Rozaini Othman (Guru Cemerlang Biologi)

Common problems among students (majority)

2012-01-01T01:34:00.002+08:00

Poor memory
Procrastination
Laziness
Addicted to computer games, TV internet
Difficulty in understanding what is taught
Easily distracted
Short attention span
Day-dreaming
Exam anxiety
Making careless mistakes
Pressure stress from parents
Too much to study and not enough time
Lack of motivation
Give up easily
Boring teachers
No interest in what they are learning

A Successful Student

2011-12-08T23:04:00.001+08:00

Introduction

The school is a friendly place; but it is also a competitive environment. The education you receive there, and the attitudes you develop, will guide you in futute. Your grades will be important. To be a successful student requires certain skills; but, these are skills that can be learned.

The Basics of Being a Good Student

- Prioritise your life: Doing well in school should be your top priority.

- Study: There is no substitute.

- Always attend class.

- Do all of the homework and assigned reading.

- Develop self-discipline.

- Manage your time.

Self-Discipline Made Easy

Human beings are creatures of habit. Therefore, form a habit of doing what you reason you should do. Is it not foolish for your behaviour to contradict your own reasoning? And what could be more harmonious than finding yourself wanting to do what you know you should?

Train yourself so there is an immediate reaction-mechanism within you:

You reason that you should do something, and thus you do it.

Other people who seem to have less difficulty with self-discipline probably have simply had more practice at it, thereby making it less difficult; because, practice is what it takes.

Time Management

No matter how you slice it, there are only 24 hours in a day. Good time-management requires:
1. Note taking on more than you can handle.
2. Reasonably estimating the time required to perform each of the tasks at hand.
3. Actually doing what needs to be done.

Only you can do these things. A couple of thoughts, though, that may help spur you on:
- A minute now is as precious as a minute later. You can't put time back on the clock.
- If you're not ahead of schedule, then you're behind schedule. Because, if you try to remain right on schedule, then any mishap or misjudgment will cause you to fall behind---perhaps right at the deadline, when no recovery is possible.

Introspection
- Understand, and be honest with, yourself. All else follows from this.
- Be both athlete and coach: Keep one eye on what you are doing, and one eye on yourself.
- Take command of, and responsibility for, yourself.
- Face your insecurities head-on. Some common signs of insecurity: Asking a question to which you already know the answer; being artificially social with teachers or other students, when the real reason is to temporarily kill the pain.
- Form a positive self-image: Those students who are first entering secondary school will probably have doubts about how well they will do. Try to do well immediately to instill an expectation of continuing to do well. Settle for nothing less. Nevertheless, try not be restricted by your past performance and experiences, good or bad. Learn from the past, but don't be bound by it. Seek out your weaknesses and attack them. Be realistic about your limitations; but, don't let this lead to becoming satisfied with them.

Taking a Course

Each student's attitude is some mixture of the following:
- He/She wants to learn the material.
- He/She wants to get a good grade.
- He/She doesn't care.

Each teacher's attitude is some mixture of the following:
- He/She wants students to learn the material.
- He/She wants grading to be fair and reflect students' knowledge and abilities.
- He/She doesn't care.

In order to do well, it is up to you (the student) to do two things:
- Learn the material.
- Learn the teacher.

As for the latter, pay attention in class to the teacher's patterns, to what he/she emphasises, etc. Gather information about the teacher from other students. A good teacher, however, will present their subject in such a way that it will be of little benefit for the student to try to learn him/her, thereby forcing their students to learn the material.

Homework
- Keep in mind that your work is being graded by a human being. Thus:
Write legibly, orderly, and coherently.
Supply any commentary necessary to make it clear what you are attempting to do.
- Making the teacher's job easier will more likely lead to you getting the benefit of doubt when it occurs.
- Don't think that getting the right answer to a homework problem implies that you have mastered the corresponding material. All you have done is solve one particular problem; that does not mean you have necessarily learned how to solve all such problems (such as the ones to appear on your exams). It's up to you to view the homework problems from this wider perspective.
- If available, always go over the solutions provided by the teacher, even if you did well on the assignment. He/She may demonstrate methods (perhaps more efficient) or provide useful information that you hadn't thought of.
Exams
- Preparation:
Roughly prioritise material as to its importance (primary, secondary, tertiary), and concentrate your studying on the most significant topics. Remember, the teacher only has a limited amount of time to test what you know and can do. Thus, keep in mind when preparing for an exam that the problems cannot be too complicated if they are to fit within the allotted time.
- Study in ways that are suited to you.
Study with a group or alone based upon which is really best for you.
Do your most strenuous and important work during those times of the day that you work best.
Summarise or outline the course or text material in your own words. Writing a summary not only forces you to examine the subject matter in detail, but provides a compendium to review just prior to the exam.
Play it safe: Memorise somewhat more than what the teacher says is required. Bring a calculator even if it's not suggested. Etc.
Study old exams if the teacher is known to give similar exams. But, don't be fooled into thinking that since you were able to work through an old exam, it means you understand all the course material in general, and can perform in a test situation.
Bring your own paper and a watch.
Fighting exam anxiety: Convince yourself that all you can do is all you can do; but, don't let that lead you to become complacent. Just be determined to be "on" for the duration of the exam. (Give yourself a pep-talk to this effect prior to each exam.)
- Starting the exam:
Read the instructions thoroughly and carefully.
Skim over the entire exam prior to beginning work.
Don't necessarily do the problems in order. Instead, get those problems out of the way you feel confident you can do quickly and well. Observe how the problems are weighted, and direct your efforts to where you believe you can pick up points most easily. This does not necessarily mean attempting the most heavily weighted problem first; rather, it means first doing the problem for which you can accumulate points at the fastest rate. Indeed, there is a good chance that this is not the most heavily weighted problem, since many instructors dislike giving any one problem significantly greater or fewer points than the average, thereby underweighting the harder problems and overweighting the easier ones.
Before writing on any given problem, think. A small investment in time at the beginning can save time overall (for you might thereby choose a more efficient method of solving the problem).
Do precisely what is requested. In particular, don't waste time doing things that will not receive credit. For example, unless explicitly required, do not rewrite the exam problems on your paper.
Pace yourself through the exam. Example: On a 50-minute exam worth a 100 points, you should be accumulating 2 points per minute; thus, a 26-point problem should be completed in 13 minutes. Do this calculation at the start of the exam if the problem weights are given.
Show your work and make clear your reasoning in order to have a chance to receive partial credit.
As with homework, and even more importantly, neatness counts.
Always check over your answers if you have time.

Further Suggestions

Unify and simplify your knowledge: A textbook presents the subject in a particular form, as does a teacher. By their very natures, however, textbooks and teachers tend to present subjects sequentially. Take the extra step of understanding the material in your terms, which may involve recognising relationships that could not be conveniently expressed in the order presented in the text(s) and lessons.
Remember, almost every logically consistent topic is simple at its foundation. Try to recognise the simple underlying relationships in the subject at hand; these are often left unstated by instructors and textbooks.
Try to learn general principles and methods. Learning by examples (putting the new in terms of the familiar) can only take you so far.
Learn as many methods of problem-solving as you can. This is especially helpful for exams, when time is of the essence.
Ask yourself questions. Why didn't the teacher or text(s) do this or that? Explore your own ideas. Try to understand the subject content in detail.
It is often said that the best way to learn something is to teach it. Do you know the subject matter well enough to explain it clearly and completely to someone else?
Learn by observing others. Notice what works for them and consider incorporating those methods into yourself. Ask yourself "Why didn't I think of that?", and try to develop the related ability.
Attempt to be methodical, neat, legible, deliberate, precise, knowledgeable, and reliable on the one hand, and creative, spontaneous, imaginative, smart, clever, articulate, and flexible on the other. The first mentality thrives on order, and inherently tries to do well what it already knows how to do; the second mentality thrives on disorder, and inherently tries to expand upon its abilities. Adopt the best of these two mentalities. Remember, every tool is a potential crutch. The first mentality may rely too heavily on already-mastered skills; but, the second mentality may fail to carefully apply those same skills.
Think about and question everything, even the statements appearing here (and, yourself!). But, realise that it is equally foolish to be different merely for the sake of being different, as it is to mindlessly conform to the norm.
For maximum efficiency, have several projects going at once. Then, if you get tired, frustrated, or bored working on one item, you can easily move onto something else, thereby staying productive as well as giving pending problems a chance to work themselves out subconsciously.
Anticipate. For example, you may need to ask the instructor about the present assignment, but he/she is only guaranteed to be available at certain times; therefore, you should look over the assignment early.
Forget pulling "all-nighters". These merely amount to borrowing from tomorrow, at which time you will find yourself considerably less functional. All-nighters are really an indication of not having properly planned your activities.
If possible, bring your textbook(s) to class.
Take your lessons notes in pencil, since any modifications can then be made quickly and neatly.

Closing

Overall, there is one basic trait that distinguishes successful students from those that are not:

Successful students force themselves to understand.

They do not merely go through the motions of attending class, reading the text(s), and doing the homework, expecting these actions to necessarily suffice. Rather, they are continually asking, "Do I really understand what's going on here?" They ask this question of themselves honestly, applying an internal barometer formed from experience to detect the slightest lack of understanding, be it ignorance or confusion. And, if the answer is "No", then the situation is viewed as unacceptable, and more effort is the response.

Facts about cell

2011-11-17T23:55:00.001+08:00

Cells are the fundamental units of life. Whether they be unicellular or multicellular life forms, all living organisms are composed of and depend on cells to function normally. Scientists estimate that our bodies contain anywhere from 75 to 100 trillion cells. Cells do everything from providing structure and stability to providing energy and a means of reproduction for an organism. The following facts about cells will provide you with well known and perhaps little known tidbits of information about cells.

1. Cells are too small to be seen without magnification.

Cells range in size from 1 to 100 micrometers. The study of cells, also called cell biology would not have been possible without the invention of the microscope. With the advance microscopes of today such as the Scanning Electron Microscope and Transmission Electron Microscope, cell biologists are able to obtain detailed images of the smallest of cell structures.

2. There are two primary types of cells.

Eukaryotic and prokaryotic cells are the two main types of cells. Eukaryotic cells are called so because they have a true nucleus. Animals, plants, fungi and protists are examples of organisms that are composed of eukaryotic cells. Prokaryotes include bacteria and archaeans.

3. Prokaryotic single-celled organisms were the earliest and most primitive forms of life on earth.
Prokaryotes can live in environments that would be deadly to most other organisms. They are able to live and thrive in various extreme habitats. Archaeans for example, live in areas such as hydrothermal vents, hot springs, swamps, wetlands, and even animal intestines.

4. There are more bacterial cells in the body than human cells.
Scientists have estimated that about 95% of all the cells in the body are bacteria. The vast majority of these microbes can be found within the digetive tract.

5. Cells contain genetic material.

Cells contain DNA (deoxyribonucleic acid), the genetic information necessary for directing cellular activities. DNA is a type of molecule known as a nucleic acid. In prokaryotic cells, the single bacterial DNA molecule is not separated from the rest of the cell but coiled up in a region of the cytoplasm called the nucleoid region. In eukaryotic cells, DNA molecules are located within the cell's nucleus. DNA and proteins are the major components of chromosomes. Human cells contain 23 pairs of chromosomes (for a total of 46). There are 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes. The X and Y sex chromosomes determine gender.

6. Cells contain structures called organelles which carry out specific functions.

Organelles have a wide range of responsibilities within a cell that include everything from providing energy to producing hormones and enzymes. Eukaryotic cells contain several types of organelles, while prokaryotic cells contain a few organelles (ribosomes) and none that are bound by a membrane. There are also differences between the kinds of organelles found within different eukaryotic cell types. Plant cells for example, contain structures such as a cell wall and chloroplasts that are not found in animal cells. Other examples of organelles include:

Nucleus
Mitochondria
Endoplasmic Reticulum
Golgi Complex
Ribosomes

7. Different types of cells reproduce through different methods.
Most prokaryotic cells reproduce by a process called binary fission. This is a type of cloning process in which two identical cells are derived from a single cell. Eukaryotic organisms have a similar type of reproductive method known as mitosis. Some eukaryotes also have the ability to reproduce sexually, which involves the fusion of sex cells or gametes. Gametes are produced by a process called meiosis.

8. Groups of similar cells form tissues.
Tissues are groups of cells with both a shared structure and function. Cells that make up animal tissues are sometimes woven together with extracellular fibers and are occasionally held together by a sticky substance that coats the cells. Different types of tissues can also be arranged together to form organs. Groups of organs can in turn form organ systems.

9. Cells have varying life spans.
Cells within the human body have different life spans based on the type and function of the cell. They can live anywhere from a few days to a year. Certain cells of the digestive tract live for only a few days, while some immune system cells can live for up to six weeks. Pancreatic cells can live for as long as a year.

10. Cells commit suicide.

When a cell becomes damaged or undergoes some type of infection, it will self destruct by a process called apoptosis. Apoptosis works to ensure proper development and to keep the body's natural process of mitosis in check. A cell's inability to undergo apoptosis can result in the development of cancer.

Respiration in Plants

2011-11-04T23:53:00.002+08:00

Plants also respire aerobically to obtain energy for metabolism. They derive most energy from cellular respiration.

During cellular respiration, energy is obtained by breaking down glucose. The energy released is stored in ATP molecules.

Although plants cannot photosynthesise without sunlight, respiration continues because plants need energy constantly to sustain vital living processes.

Gaseous exchange between plant cells and the environment occurs by diffusion mainly through the stomata and lenticels. Respiratory gases enter and leave plants via stomata in the epidermis of the leaves and the stems of herbaceous plants. Lenticels are raised pores found on the stems and roots of plants.

When stomata are open, they connect the air spaces within the leaves to the atmosphere.

Oxygen from the atmosphere diffuses into the air spaces and then dissolves in the film of water around the mesophyll cells.

Oxygen is then used in aerobic respiration.

The concentration of oxygen in the cells becomes lower than the concentration of oxygen in the air spaces.

The difference in concentration gradient allows oxygen to diffuse continuously from the air spaces into the cells.

During the day, the carbon dioxide which is produced during aerobic respiration is used in photosynthesis.

The excess carbon dioxide diffuses into the air spaces and then through the stomata into the atmosphere.

Aerobic respiration is usually carried out by all plants throughout the day and night.

However, under certain conditions, plants can carry out anaerobic respiration for short periods.

For example, in flood.

Anaerobic respiration also occurs during initial stages of seed germination.

Respiration and photosynthesis are interdependent. Photosynthesis produces the raw materials required by respiration and respiration produces the raw materials required by photosynthesis.

As light intensity increases during the day, the rate of photosynthesis also increases. Eventually a point reached at which all carbon dioxide produced during respiration is used in photosynthesis. At this point, there is no net gain or net loss in the sugar produced. The plant has reached a compensation point.

The compensation point is the light intensity at which the rate of carbon dioxide production during respiration is equal to the carbon dioxide consumption during photosynthesis.

As light intensity continues to increase during the day, the rate of photosynthesis exceeds the rate of respiration. The carbon dioxide produced during respiration is no longer sufficient fro the plants. Plants must take in carbon dioxide from the atmosphere to supplement the need for a higher concentration of carbon dioxide during photosynthesis. At the same time plants release the excess oxygen into the atmosphere.

Pathogen

2011-10-22T00:26:00.000+08:00

A microorganism that affects the human host sufficiently to cause disease or death is called a "pathogen." Not all parasites, for example, are pathogens, and not all pathogens have a parasitic origin. An example of a non-parasitic pathogen is Clostridium botulinum. Some pathogens are the result of fungi, some of viruses, or protozoa, as well as bacteria.

Anthrax infection, for example, happens only by certain strains of Bacillus anthracis, which contains plasmids that encode the anthrax toxin. It is also encapsulated, protecting the pathogen. Opportunistic pathogens are those organisms that are usually a part of the body's natural flora and only become harmful after an invasion, as when surgery or accidental injury takes place.

Different pathogens act in different ways. Some produce toxins, while others invade cells or tissues and then produce toxins. Even when localized in the body, such infections can have systemic effects. Symptoms are often a result of the body over-reacting in its own defence. For instance, inflammation is an important part of the body's natural reaction to pathogens and is a response to a signal that there is a problem in a certain area. Defences are sent to increase the exposure of a pathogen to the body's own antimicrobial factors.

How does a pathogen cause disease? The following are just a few diseases to show how a pathogen works on the body.

Botulism causes muscle paralysis and death, mainly because of respiratory failure. The pathogen (strains of Clostridium botulinum) form a toxin that binds to nerve-muscle junctions, stopping the release of acetylcholine which stimulates the muscles.

>Cholera produces vomiting and profuse watery diarrhea. The pathogen causing this are strains of Vibrio cholerae, which multiply in the intestines, forming an enterotoxin which acts on the mucosal cells in the small intestine. Within the mucosal cells, the toxin stimulates an enzyme (adenylate cyclase), which causes an increase in cellular cAMP. This, in turn, leads to a massive outflow of electroytes (Na + Cl) and water into the lumen of the intestine, resulting in massive and rapid dehydration.

Cystic fibrosis is a hereditary disease characterized by severe bronchial congestion. In some cases, the respiratory tract becomes colonized by certain strains of Pseudomonas aeruginosa, which produce an abundant supply of mucusy slime that dramatically diminishes the probability of survival.

E. coli strains invade and destroy cells in the small intestine and colon, producing abdominal pain; profuse watery diarrhea; and ultimately, rapid dehydration. Some strains can even produce a toxin after adhering to the mucosal tissues of the intestine.

Oroya fever (Bartonella bacilliformis), occurring in some parts of South America, produces fever and anemia. It is transmitted through the bites of sandflies. The bacterium grows in and on erythrocytes (red blood cells) and in the endothelial cells (cells that line the cavities of the heart, blood, and lymph vessels, as well as some cavities of the body) of the host. As the bacteria invade the red blood cells, they cause the death of the cells, producing anemia.

Tetanus causes uncontrollable contractions of skeletal muscles, often leading to death from asphyxiation or exhaustion. The disease develops when wounds are contaminated with the pathogen Clostridium tetani, which produces a toxin called tetanospasmin. This toxin acts on certain cells in the CNS, preventing the release of glycine which permits muscles to move as they should.

Typhoid is caused by Salmonella typhi, which produces intestinal symptoms and septicaemia or blood poisoning. After ingestion, the pathogen invades mucosa in the small intestine. In some cases, the ileum becomes so inflamed that it causes necrosis or death of the tissue, producing hemorrhaging.

Bacterial pathogens and the diseases they cause:

Legionella pneumophila (pneumonia)

Neisseria gonorrhoeae (gonorrhea)

Mycoplasma pneumoniae (pneumonia)

Mycoplasma hominis (UTI's, PID)

Mycobacterium tuberculosis (tuberculosis)

Mycobacterium avium (tuberculosis)

Chlamydia trachomatis (venereal syndromes, trachoma)

Listeria monocytogenes (Listeriosis)

Salmonellae spp. (GI disorders)

Shigella spp. (GI disorders)

Escherichia coli (enteropathogenic strains) (GI disorders)

Yersinia enterocolitica (GI disorders)

Staphylococcus aureus (purulent discharges - boils. Blisters, pus-forming skin infections)

Staphylococcus pyogenes (Scarlet/rheumatic fever, "strep" throat).

Viral pathogens and the diseases they cause:

Hepatitis A,B,C,D (hepatitis)

Human immunodeficiency virus -- HIV (AIDS)

Cytomegalovirus (congenital viral infections, mononucleosis)

Epstein-Barr virus (Burkitts lymphoma and other lymphoproliferative diseases)

Herpes virus - types I and II (cold sores, genital herpes)

Human papilloma virus (genital warts, cervical cancer).

Protozoal pathogens and the disease they cause:

Leishmania donovanii (Leishmaniasis)

Plasmodium spp. (malaria)

Pneumocystis carinii (pneumonia)

Trypanosoma spp. (trypanosomiasis).

Infectious diseases, agents, and estimated yearly deaths:

Data, from WHO, displays the yearly worldwide deaths from each disease during the decade preceeding its publication in 1992. There are approximately fifty million deaths per year worldwide from all causes.

Acute respiratory infections (bacteria, viruses, protozoa, fungi) (6,900,000)

Diarrheal diseases (bacteria, viruses) (4,200,000)

Tuberculosis (bacteria) (3,300,000)

Malaria (protozoa) (1-2,000,000)

Hepatitis (viruses) (1-2,000,000)

Measles (virus) (220,000)

Meningitis (bacteria) (200,000)

Schistosomiasis (parasitic worm) (200,000)

Pertussis - whooping cough (bacterium) (100,000)

Amoebiasis (protozoa) (40,000-100,000)

Hookworm (parasitic worm) (50-60,000)

Rabies (virus) (35,000)

Yellow fever (virus) (30,000)

African trypanosomiasis - sleeping sickness (protozoan) (20,000+).

Viruses and Bacteria

2011-10-01T22:18:00.000+08:00

What are viruses?

Viruses are too small to be seen by the naked eye. They can't multiply on their own, so they have to invade a 'host' cell and take over its machinery in order to be able to make more virus particles.

Viruses consist of genetic materials (DNA or RNA) surrounded by a protective coat of protein. They are capable of latching onto cells and getting inside them.

The cells of the mucous membranes, such as those lining the respiratory passages that we breathe through, are particularly open to virus attacks because they are not covered by protective skin.

What are bacteria?

Bacteria are organisms made up of just one cell. They are capable of multiplying by themselves, as they have the power to divide. Their shapes vary, and doctors use these characteristics to separate them into groups.

Bacteria exist everywhere, inside and on our bodies. Most of them are completely harmless and some of them are very useful.

But some bacteria can cause diseases, either because they end up in the wrong place in the body or simply because they are 'designed' to invade us.

How are infections with viruses and bacteria spread?

Viral and bacterial infections are both spread in basically the same ways.

A person with a cold can spread the infection by coughing and/or sneezing.
Bacteria or viruses can be passed on by touching or shaking hands with another person.
Touching food with dirty hands will also allow viruses or bacteria from the intestine to spread.
Body fluids, such as blood, saliva and semen, can contain the infecting organisms and transmission of such fluids, for example by injection or sexual contact, is important, particularly for viral infections like hepatitis or AIDS.

How to avoid infection

Wash your hands thoroughly (often one of the best ways to avoid catching a cold).
Shaking hands with someone who has a cold is risky, so avoid rubbing your eyes or nose afterwards.
Food should be cooked or cooled down as quickly as possible.
Vegetables and meat must be stored separately and prepared on separate chopping boards.
Meat should preferably be served well-done.
Remember that food with these invisible organisms does not necessarily smell bad.
Some organisms are killed as the food is cooked, but they can still leave toxic substances that may cause diarrhoea and vomiting.
The use of condoms during sexual intercourse reduces the likelihood of spreading sexually transmitted diseases.

How can the doctor treat bacterial infections?

Bacterial infections are usually treated with a special antibiotic, which only kills the bacterium that has caused the disease.

To make sure that you get the right treatment, your doctor may take a sample, for example a swab from the throat or a urine sample.

How can the doctor treat viral infections?

Viruses can't multiply until they are inside the body's cells.

This is the reason why the treatment of virus infections is usually left up to the patient's own immune system, although it may be hard to accept when the doctor says the only cure is for 'nature to take its course'.

The treatment of virus infections, such as influenza, will usually involve:

drinking plenty of water
staying at home. People who go to work or school in this condition not only risk spreading the virus to their colleagues but also run a higher risk of catching a bacterial infection
taking a painkiller, such as paracetamol (eg Panadol) or ibuprofen (eg Nurofen), to bring your temperature down
vaccines have been developed against most viral diseases. The vaccine gives the body some help in quickly and effectively fighting the virus.

An increasing number of antiviral remedies are being developed that prevent the virus multiplying and cause the illness to run its course more quickly.

Unfortunately, these remedies can still only be used on very few viruses and are of limited effectiveness.

Antibiotics have no effect upon viral infections such as colds or flu, and it's important that we limit antibiotic use only to bacterial infections that won't get better on their own.

Over-use of antibiotics reduces their effectiveness by encouraging the growth of antibiotic-resistant bacteria, which is a serious and increasing problem globally.

CFS

2011-09-28T22:46:00.000+08:00

Chronic Fatigue Syndrome is a state of chronic tiredness that happens without explanation for 6 months or more. About 200 out of 100,000 adults in the U.S have this syndrome. It occurs more in middle aged adults then adolescents. It also occurs more in women then men. CFS is a very rare syndrome.

Besides fatigue, chronic fatigue syndrome has many symptoms. Including muscle pain, joint pain, sore throat, headache, fever, chills, tender lymph nodes, problems concentrating, memory loss and low blood pressure. CFS is also known as an immune disorder due to the fact people with this syndrome get sick easily and very often.

There is no cure to chronic fatigue syndrome. So there is only treatment options. Many doctors suggest rest, exercise and proper diet. Counseling and stress relieving activities may help. Many vitamins and some drugs are believed to help. Ibuprofen can help pain and fever that come along with CFS. Anxiety medications can calm the stress that comes with this syndrome. Overall, doctors agree that strict routine is needed.

CFS effects many parts of a person's life. People effected can not do as many activities as a normal person. Without doing things a person once enjoyed can create a depression situation. CFS also can create weight gain or loss. Many become more sensitive to light, sound, food and smells. Most people can not deal with a such change very well. The best way to get through CFS is a positive attitude.

Unfortunately, there is no cure or prevention for Chronic Fatigue Syndrome. This disorder alters many parts of a person's life and is a very serious syndrome. This syndrome can put a person in the hospital for many days. This syndrome should be more publicly known so people can identify the signs before it gets to the point of extreme exhaustion. Many people may not know they have this syndrome. It may be more common them doctors realise.

Global warming

2011-09-27T21:35:00.001+08:00

The planet is warming, from North Pole to South Pole, and everywhere in between. Globally, the mercury is already up more than 1 degree Fahrenheit (0.8 degree Celsius), and even more in sensitive polar regions. And the effects of rising temperatures aren’t waiting for some far-flung future. They’re happening right now. Signs are appearing all over, and some of them are surprising. The heat is not only melting glaciers and sea ice, it’s also shifting precipitation patterns and setting animals on the move.

Some impacts from increasing temperatures are already happening.

Ice is melting worldwide, especially at the Earth’s poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice.

Researcher Bill Fraser has tracked the decline of the Adélie penguins on Antarctica, where their numbers have fallen from 32,000 breeding pairs to 11,000 in 30 years.

Sea level rise became faster over the last century.

Some butterflies, foxes, and alpine plants have moved farther north or to higher, cooler areas.

Precipitation (rain and snowfall) has increased across the globe, on average.

Spruce bark beetles have boomed in Alaska thanks to 20 years of warm summers. The insects have chewed up 4 million acres of spruce trees.

Other effects could happen later this century, if warming continues.

Sea levels are expected to rise between 7 and 23 inches (18 and 59 centimeters) by the end of the century, and continued melting at the poles could add between 4 and 8 inches (10 to 20 centimeters).

Hurricanes and other storms are likely to become stronger.

Species that depend on one another may become out of sync. For example, plants could bloom earlier than their pollinating insects become active.

Floods and droughts will become more common. Rainfall in Ethiopia, where droughts are already common, could decline by 10 percent over the next 50 years.

Less fresh water will be available. If the Quelccaya ice cap in Peru continues to melt at its current rate, it will be gone by 2100, leaving thousands of people who rely on it for drinking water and electricity without a source of either.

Some diseases will spread, such as malaria carried by mosquitoes.

Ecosystems will change—some species will move farther north or become more successful; others won’t be able to move and could become extinct. Wildlife research scientist Martyn Obbard has found that since the mid-1980s, with less ice on which to live and fish for food, polar bears have gotten considerably skinnier. Polar bear biologist Ian Stirling has found a similar pattern in Hudson Bay. He fears that if sea ice disappears, the polar bears will as well.

Ozone layer depletion

2011-09-27T21:07:00.002+08:00

Today, one of the most discussed and serious environmental issues is the ozone layer depletion, the layer of gas that forms a protective covering in the Earth's upper atmosphere. Ozone is formed when oxygen molecules absorb ultraviolet photons and undergo a chemical reaction known as photo dissociation or photolysis, where a single molecule of oxygen breaks down to two oxygen atoms. The free oxygen atom, then combines with an oxygen molecule and forms a molecule of ozone. The ozone molecules, in turn absorb ultraviolet rays between 310 to 200 nm wavelength and thereby prevent these harmful radiations from entering the Earth's atmosphere. In the process, ozone molecules split up into a molecule of oxygen and an oxygen atom. The oxygen atom again combines with the oxygen molecule to regenerate an ozone molecule. Thus, the total amount of ozone is maintained by this continuous process of destruction and regeneration.

Ozone layer depletion first captured the attention of the whole world in the later half of 1970 and since then, many discussions and researches have been carried out to find out the possible effects and the causes of ozone depletion. Many studies have also been directed to find out a possible solution.

Causes of Ozone Depletion

The cause of ozone depletion is the increase in the level of free radicals such as hydroxyl radicals, nitric oxide radicals and atomic chlorine and bromine. The most important compound, which accounts for almost 80% of the total depletion of ozone in the stratosphere are chlorofluorocarbons (CFC). These compounds are very stable in the lower atmosphere of the Earth, but in the stratosphere, they break down to release a free chlorine atom due to ultraviolet radiation. A free chlorine atom reacts with an ozone molecule and forms chlorine monoxide and a molecule of oxygen. Now chlorine monoxide reacts with an ozone molecule to form a chlorine atom and two molecules of oxygen. The free chlorine molecule again reacts with ozone to form chlorine monoxide. The process continues and the result is the reduction or depletion of ozone in the stratosphere.

Possible Effects of Ozone Depletion

If you are wondering why is the ozone layer important, then the answer lies in the harmful effects of ultraviolet rays. The ozone layer is responsible for absorbing the ultraviolet rays and thereby preventing them from passing through the atmosphere of Earth. Ultraviolet rays of the Sun are associated with a number of health related and environmental issues. The most important of these is the association between ultraviolet rays and an increased risk of developing several types of skin cancers including malignant melanoma, basal and squamous cell carcinoma. Even the incidents of cortical cataracts can also increase significantly with the increased exposure to ultraviolet rays.

Another observation in this regard is that a decrease in the ozone in the stratosphere can lead to an increase in the ozone present in the lower atmosphere. Ozone present in the lower atmosphere is mainly regarded as a pollutant and a green house gas that can contribute to global warming and climate change. However, researches have pointed out that the lifespan of atmospheric ozone is quiet less as compared to stratospheric ozone. At the same time, increase in the surface level of ozone can enhance the ability of sunlight to synthesize vitamin D, which can be regarded as an important beneficial effect of ozone layer depletion.

The effects of ozone depletion are not limited to humans only, as it can affect animals and plants as well. It can affect important food crops like rice by adversely affecting cyanobacteria, which helps them absorb and utilize nitrogen properly. Phytoplankton, an important component of the marine food chain, can also be affected by ozone depletion. Studies in this regard have shown that ultraviolet rays can influence the survival rates of these microscopic organisms by affecting their orientation and mobility.

The increasing concern for the causes and effects of ozone depletion led to the adoption of the Montreal Protocol, in the year 1987, in order to reduce and control the industrial emission of chlorofluorocarbons. International agreements have succeeded to a great extent in reducing the emission of these compounds, however, more cooperation and understanding among all the countries of the world is required to mitigate the problem.

Carbon dioxide transport

2011-09-24T23:21:00.001+08:00

There are 3 ways in which carbon dioxide is transported in the blood:

1. Dissolved carbon dioxide

Carbon dioxide is much more soluble in blood than oxygen.

About 5 % of carbon dioxide is transported unchanged, simply dissolved in the plasma

2. Bound to haemoglobin & plasma protein

Carbon dioxide combines reversibly with haemoglobin to form carbaminohaemoglobin. Carbon dioxide does not bind to iron, as oxygen does, but to amino groups on the polypeptide chains of haemoglobin.

Carbon dioxide also binds to amino groups on the polypeptide chains of plasma proteins

About 10 % of carbon dioxide is transported bound to haemoglobin and plasma proteins

3. Bicarbonate ions

The majority of carbon dioxide is transported in this way. Carbon dioxide enters red blood cells in the tissue capillaries where it combines with water to form carbonic acid. This reaction is catalysed by the enzyme carbonic anhydrase, which is found in the red blood cells. Carbonic acid then dissociates to form bicarbonate ions (HCO3-) and hydrogen ions (H+).

The hydrogen ions, formed from the dissociated carbonic acid, combine with the haemoglobin in the red blood cell. Bicarbonate ions diffuse out of the red blood cell into the plasma whilst chloride ions (Cl-) diffuse in to take their place. This is known as the chloride shift.

The diagram above shows the reversal of the reactions which occurs at the lungs. Bicarbonate ions enter the red blood cells and combine with hydrogen ions to form carbonic acid. This is broken down into carbon dioxide and water. Carbon dioxide diffuses out of the red blood cells and into the alveoli.

Trial STPM Bio Kedah

2011-09-15T23:42:00.000+08:00

Paper 1
http://www.scribd.com/doc/65081314

Paper 2
http://www.scribd.com/doc/65081515

Mark scheme
http://www.scribd.com/doc/65081697

Biological Terms

2011-09-10T23:26:00.000+08:00

One of the keys to being successful in biology is being able to understand the terminology. Difficult biology words and terms can be made easy to understand by becoming familiar with common prefixes and suffixes used in biology. These affixes, derived from Latin and Greek roots, form the basis for many difficult biology words.

Below is a list of a few biology words and terms that many biology students find difficult to understand. By breaking these words down into discrete units, even the most complex terms can be understood.

1. Autotroph

This word can be separated as follows: Auto - troph.

Auto - means self, troph - means nourish. Autotrophs are organisms capable of self nourishment.

2. Cytokinesis

This word can be separated as follows: Cyto - kinesis.

Cyto - means cell, kinesis - means movement. Cytokinesis refers to the movement of the cytoplasm that produces distinct daughter cells during cell division.

3. Eukaryote

This word can be separated as follows: Eu - karyo - te.

Eu - means true, karyo - means nucleus. A eukaryote is an organism whose cells contain a "true" membrane bound nucleus.

4. Heterozygous

This word can be separated as follows: Hetero - zyg - ous.

Hetero - means different, zyg - means yolk or union, ous - means characterized by or full of. Heterozygous refers to a union characterized by the joining of two different alleles for a given trait.

5. Hydrophilic

This word can be separated as follows: Hydro - philic.

Hydro - refers to water, philic - means love. Hydrophilic means water-loving.

6. Oligosaccharide

This word can be separated as follows: Oligo - saccharide.

Oligo - means few or little, saccharide - means sugar. An oligosaccharide is a carbohydrate that contains a small number of component sugars.

7. Osteoblast

This word can be separated as follows: Osteo - blast.

Osteo - means bone, blast - means bud or germ (early form of an organism). An osteoblast is a cell from which bone is derived.

8. Tegmentum

This word can be separated as follows: Teg - ment - um.

Teg - means cover, ment - refers to mind or brain. The tegmentum is the bundle of fibers that cover the brain.

Pneumonoultramicroscopicsilicovolcanoconiosis

Yes, this is an actual word. What does it mean? Biology can be filled with words that sometimes seem incomprehensible. By "dissecting" these words into discrete units, even the most complex terms can be understood. To demonstrate this concept, let's begin by performing biology word dissections on the word above.

To perform our biology word dissection, we'll need to proceed carefully. First, we come to the prefix (pneu-), or (pneumo-) which means lung. Next, is ultra, meaning extreme, and microscopic, meaning small. Now we come to (silico-), which refers to silicon, and (volcano-) which refers to the mineral particles that make up a volcano. Then we have (coni-), a derivative of the Greek word konis meaning dust. Finally, we have the suffix (-osis) which means affected with. Now lets rebuild what we have dissected:

Considering the prefix (pneumo-) and the suffix (-osis), we can determine that the lungs are affected with something. But what? Breaking down the rest of the terms we get extremely small (ultramicroscopic) silicon (silico-) and volcanic (volcano-) dust (coni-) particles. Thus, pneumonoultramicroscopicsilicovolcanoconiosis is a disease of the lungs resulting from the inhalation of very fine silicate or quartz dust. That wasn't so difficult, now was it?

Now that we've honed our dissection skills, let's try some frequently used biology terms. For instance:

Arthritis

(Arth-) refers to joints and (-itis) means inflammation. Arthritis is the inflammation of a joint(s).

Erythrocyte

(Erythro-) means red and (-cyte) means cell. Erythrocytes are red blood cells.

Okay, let's move on to more difficult words. For instance:

Electroencephalogram

Dissecting, we have (electro-), pertaining to electricity, (encephal-) meaning brain, and (-gram) meaning record. Together we have an electric brain record or EEG. Thus, we have a record of brain wave activity using electrical contacts.

Schizophrenia

Individuals with this disorder suffer from delusions and hallucinations. (Schis-) means split and (phren-) means mind.

Thermoacidophiles

These are ancient bacteria that live in extremely hot and acidic environments. (Therm-) means heat, next you have (-acid), and finally (phil-) means love. Together we have heat and acid lovers.

Once you understand the commonly used prefixes and suffixes, obtuse words are a piece of cake! Now that you know how to apply the word dissection technique, I'm sure you'll be able to determine the meaning of the word thigmotropism (thigmo - tropism).

Mangrove swamps (Colonisation & Succession)

2011-09-05T13:30:00.001+08:00

Mangrove swamps are mostly found in the tropical and subtropical region where fresh-water meets salt water.
They have muddy soft soil and are a hostile environment for normal plants. This is because the soil has very low levels of oxygen and a high concentration of salt.
In addition, mangrove swamps are exposed to high intensities of sunlight and strong winds.

The pioneer species of a mangrove swamp are the Sonneratia sp. and Avicennia sp.

Sonneratia sp.

Avicennia sp.

The presence of this species gradually changes the physical environment of the habitat.

Rhizophora sp.

The extensive root systems of these plants trap and collect sediments, including organic matter from decaying plant parts.

As time passes, the soil becomes more compact and firm. This condition favours the growth of Rhizophora sp. Gradually the Rhizophora sp. replaces the pioneer species.

The prop root system of the Rhizophora sp. traps silt and mud, creating a firmer soil structure over time.
The ground becomes higher. As a result, the soil is drier because it is less submerged by sea water.
The condition now becomes more suitable for the Bruguiera sp., which replaces the Rhizophora sp.

Bruguiera sp.

The buttress root system of the Bruguiera sp. forms loops which extend from the soil to trap more silt and mud.
As more sediments are deposited, the shore extends further to the sea. The old shore is now further away from the sea and is like terresterial ground.
Over time, terrestrial plants like nipah palm and Pandanus sp. begin to replace the Bruguiera sp.

Ecosystem

2011-09-05T13:19:00.000+08:00

An ecosystem is a community of living organisms interacting with one another and with non-living organisms.

A habitat is the natural environment in which an organism lives.

A species consists of a group of organisms that look alike and have similar characteristics, share the same ecological niche and are capable of interbreeding.

A population consists of organisms living in the same habitat at the same time.

A community is a natural collection of plant and animal species living within a defined area or habitat in an ecosystem.

The function of an organism or the role it plays in an ecosystem is known as the ecological niche.

Cancer

2011-08-21T23:54:00.000+08:00

Causes
There are about 200 different types of cancer. They can start in any type of body tissue. What affects one body tissue may not affect another. For example, tobacco smoke that you breathe in may help to cause lung cancer. Overexposing your skin to the sun could cause a melanoma on your leg. But the sun won't give you lung cancer and smoking won't give you melanoma.

Apart from infectious diseases, most illnesses are 'multifactorial'. Cancer is no exception. Multifactorial means that there are many factors involved. In other words, there is no single cause for any one type of cancer.

Carcinogens
A 'carcinogen' is something that can help to cause cancer. Tobacco smoke is a powerful carcinogen. But not everyone who smokes gets lung cancer. So there must be other factors at work as well as carcinogens.

Age
Most types of cancer become more common as we get older. This is because the changes that make a cell become cancerous in the first place take a long time to develop. There have to be a number of changes to the genes within a cell before it turns into a cancer cell. These changes can happen by accident when the cell is dividing. Or they can happen because the cell has been damaged by carcinogens and the damage is then passed on to future 'daughter' cells when that cell divides. The longer we live, the more time there is for genetic mistakes to happen in our cells.

Genetic make-up
There need to be a number of genetic mutations within a cell before it becomes cancerous. Sometimes a person is born with one of these mutations already. This doesn't mean they will definitely get cancer. But with one mutation from the start, it makes it more likely statistically that they will develop cancer during their lifetime. Doctors call this 'genetic predisposition'.

The BRCA1 and BRCA2 breast cancer genes are examples of genetic predisposition. Women who carry one of these faulty genes have a higher chance of developing breast cancer than women who do not.

The BRCA genes are good examples for another reason. Most women with breast cancer do not have a mutated BRCA1 or BRCA 2 gene. Less than 5% of all breast cancer is due to these genes. So although women with one of these genes are individually more likely to get breast cancer, most breast cancer is not caused by a high risk inherited gene fault.

This is true of other common cancers where some people have a genetic predisposition - for example, colon (large bowel) cancer.

Researchers are looking at the genes of people with cancer in a study called SEARCH. They also hope to find out more about how other factors might interact with genes to increase the risk of cancer. Information about this study is on our clinical trials database.

The Immune System
People who have problems with their immune systems are more likely to get some types of cancer. This group includes people who

* Have had organ transplants and take drugs to suppress their immune systems to stop organ rejection
* Have HIV or AIDS
* Are born with rare medical syndromes which affect their immunity

The types of cancers that affect these groups of people fall into two, overlapping groups

* Cancers that are caused by viruses, such as cervical cancer and other cancers of the genital or anal area, some lymphomas, liver cancer and stomach cancer
* Lymphomas

Chronic infections or transplanted organs can continually stimulate cells to divide. This continual cell division means that immune cells are more likely to develop genetic faults and develop into lymphomas.

Bodyweight, diet and physical activity
Cancer experts estimate that maintaining a healthy bodyweight, making changes to our diet and taking regular physical activity could prevent about one in three deaths from cancer in the UK. In the western world, many of us eat too much red and processed meat and not enough fresh fruit and vegetables. This type of diet is known to increase the risk of cancer. Drinking alcohol can also increase the risk of developing some types of cancer. There is more information about this in the page on diet causing cancer.

Sometimes foods or food additives are blamed for directly causing cancer and described as 'carcinogenic'. This is often not really true. Sometimes a food is found to contain a substance that can cause cancer but in such small amounts that we could never eat enough of it to do any harm. And some additives may actually protect us. There is more about food additives in the page on diet causing cancer.

Day to day environment
By environmental causes we mean what is around you each day that may help to cause cancer. This could include

* Tobacco smoke
* The sun
* Natural and man made radiation
* Work place hazards
* Asbestos

Some of these are avoidable and some aren't. Most are only contributing factors to causing cancers - part of the jigsaw puzzle that scientists are still trying to put together. There is more about this in the page on causes of cancer in the environment.

Viruses
Viruses can help to cause some cancers. But this does not mean that these cancers can be caught like an infection. What happens is that the virus can cause genetic changes in cells that make them more likely to become cancerous.

These cancers and viruses are linked

* Cervical cancer, and other cancers of the genital and anal area, and the human papilloma virus (HPV)
* Primary liver cancer and the Hepatitis B and C viruses
* Lymphomas and the Epstein-Barr Virus
* T cell leukaemia in adults and the Human T cell leukaemia virus
* HPV also probably leads to oropharyngeal cancer and non melanoma skin cancers in some people

There will be people with primary liver cancer and with T cell leukaemia who haven't had the related virus. But infection increases their risk of getting that particular cancer. With cervical cancer, scientists now believe that everyone with an invasive cervical cancer has had an HPV infection beforehand.

Many people can be infected with a cancer causing virus, and never get cancer. The virus only causes cancer in certain situations. Many women get a high risk HPV infection, but never develop cervical cancer. Another example is Epstein-Barr virus (EBV). These are some facts about EBV

* It is very common - most people are infected with EBV
* People who catch it late in life get glandular fever and have an increased risk of lymphoma
* In sub-Saharan Africa, EBV infection and repeated attacks of malaria together cause a cancer called Burkitt's lymphoma in children
* In China, EBV infection (together with other unknown factors) causes nasopharyngeal cancer
* In people with AIDs and transplant patients EBV can cause lymphoma
* About 4 out of 10 cases of Hodgkin's lymphoma and a quarter of cases of Burkitt's lymphoma (a rare type of non Hodgkin's lymphoma) seem to be related to EBV infection.

Bacterial infection
Bacterial infections have not been thought of as cancer causing agents in the past. But studies have shown that people who have helicobacter pylori infection of their stomach develop inflammation of the stomach lining, which increases the risk of stomach cancer. Helicobacter pylori infection can be treated with a combination of antibiotics.

Research is also looking at whether substances produced by particular types of bacteria in the digestive system can increase the risk of bowel cancer or stomach lymphomas. Some researchers think that particular bacteria may produce cancer causing substances in some people. But research into this issue is at an early stage.

If bacteria do play a part in causing cancer this could be important in cancer prevention. Bacterial infections can often be cured with antibiotics, so getting rid of the infection could be a way to reduce the risk of these types of cancer.

P3 Answering Technique

2011-08-10T23:40:00.003+08:00

Question 1
Observation
In 0.2M of sucrose solution, the final diameter of potato disc is 1.90 cm.
In 0.6M of sucrose solution, the final diameter of potato disc is 1.40 cm.
Your answer must be specific. Where do u get it?? From the title in the given table.

Inference
(At 0.2M of sucrose solution) water molecule diffuses into the potato disc by osmosis.
(At 0.6M of sucrose solution) water molecule diffuses out of the potato disc by osmosis.
You give reasons (why) based on your observation. But remember, inference 1 for observation 1 and inference 2 for observation 2. Jgn. silap, rugi....potong markah

Variables
Manipulated variable
Concentration of sucrose solution : Use five different concentrations of sucrose solutions

Responding variable
Final diameter of the potato disc : Measure and record the final diameter of potato disc by using a metre rule
The word record and the instrument used are important.
//
Percentage change in diameter of potato disc : Calculate the percentage change in diameter of potato disc
by using the formula :
(Final – Initial) diameter of potato disc x 100%
Initial diameter of potato disc
If you choose to write about the formula, must state clearly

Constant variable
Time taken to immerse the potato discs : Fix the time (to immerse the potato discs) at 20 minutes.
If the exact time or units are stated in the question, students must write them down. If not, telor ayam la....

Hypothesis
As the concentration of sucrose solution increases, the final diameter of potato disc / the percentage change in diameter decreases.
Just the MV + RV and the relationship(higher, lower); no need to explain further.
Majority of the students like to write `depends on', `affects', `influences'....style PMR.....1 mark only

Table
1. Title and units (must be correct)
No units will be given in the question. Students must refer the earlier page.
2. Apply readings from the table given earlier.(salin jer)
3. Some calculation.

Graph
1. Both axes with correct units and title
2. All points plotted correctly (don't simply add any readings on you own; eg. connect it to 0 ka...)
3. Smooth curve touching all points.

Relationship
The concentration of sucrose solution which is isotonic to the cell sap of potato disc is *0.49M. The percentage change in diameter is zero because
the rate of water that diffuses in and out of the cell is equal.
Must explain.

Prediction
Diameter (of potato disc) is more than 1.9 cm
Distilled water is hypotonic to the cell sap of potato disc
so more water diffuses into the potato (disc) by osmosis.
We predict more or less by referring to the data from the earlier page. Don't simply guess.

Operational definition (Give explanation based on the experiment; not theoretically. Normally combine CV,MV & RV)
Osmosis is the movement of water to / from potato disc through the plasma membrane (of potato) due to the difference concentration between sucrose solution and cell sap of potato cell that will result in changes / decrease / increase in diameter of potato disc.

We don't write osmosis is the movement of water molecules from the region of `high water concentration/low solute concentration' to the region of `low water concentration/high solute concentration' through the semi permeable membrane....as in the book (theory)

Classifying
Salin balik je...dlm kotak....kacang

Total : 33 marks

Question 2 (Latest format)
Eg.
Plan a laboratory experiment to investigate the percentage of vitamin C content in each fruit. DCPIP (dichlorophenolindophenol) 0.1% solution is used to test the presence of vitamin C in the fruit juices.
[Apple, Orange, Watermelon]

Problem statement (3 marks)
1. What is the percentage of vitamin C content in watermelon, orange and apple?/ fruits? //
2. Does apple/orange/watermelon contain more vitamin C than orange/watermelon/apple? //
3. Which fruit has more percentage of vitamin C?
(Remember, all must be in question form. Change the aim into a question form. (kacang). No question mark, deduce 1 mark)

Hypothesis (MV+RV+R) (3 marks)
Watermelon has highest content of vitamin C compare to other fruits.

Materials & Apparatus (3 marks)
DCPIP solution, Standard Ascorbic Acid, Fruit juices / watermelon juice/orange juice/apple juice, Conical flask /beaker, Syringe with needle, Specimen tube

Procedure (3 marks)
K1 : Steps to set up the apparatus & materials
K2 : Steps to handle the fixed variable
K3 : Steps to handle the manipulated variable
K4 : Steps to handle the responding variable
K5 : Precautionary steps / steps taken to get accurate results / readings
(Examiners will be looking for all these 5Ks to get 3 marks )

Eg.
K1 1. Three specimen tubes is labelled as A1, A2 and A3.
K2 2. Fill each specimen tubes with 1 ml of 0.1% DCPIP solution
K1 3 . Use a syringe to take 10 ml of standard ascorbic acid
K1 4 . Place the syringe needle into the DCPIP solution and release the ascorbic acid slowly into the DCPIP solution in A1
K4 5 Observe the change of DCPIP colour and stop releasing the ascorbic acid when the DCPIP become colourless/ no more blue traces
K4 6 Record the volume of ascorbic acid used to dicolourise the DCPIP solution.
K1/K5 7 Repeat steps 3 – 6 for A2 and A3 and calculate the average volume.
K1/K5 8 Juices from each of the fruits is obtained and kept fresh before used
K1/K2 9 Three specimen tubes is labelled as (B1, B2, B3, C1, C2, C3, D1, D2 and D3), and fill each specimen tubes with 1 ml of 0.1% DCPIP
K3 10 Repeat steps 2 – 7 by using fruit juices to replace the standard ascorbic acid.
K5 11 Do not shake the bottle to prevent from DCPIP is oxidated.
K4 12 Record the volume of watermelon juice, apple juice and orange juice that discolourise the DCPIP in the table and calculate the average volume
K4 13 Calculate the percentage of vitamin C in each of the fruit juice using the formula below:

Percentage of vitamin C in fruit juice =
volume of 0.1% ascorbic acid X 1.0 mgcm-1
volume of fruit juice

Tak payah tulis all the Ks in front. For reference only.

Presentation of Data (2 marks)

No data is required. Just the title and the correct units.
Total : 17 marks

Studying skills in Biology

2011-08-07T23:57:00.000+08:00

1. Successful biology students study a minimum of 2 to 3 hours per day, 7 days a week, throughout the term.

2. Biology is hard work, so be aggressive. Take it as a challenge and give it your time and your energy.

3. Know and understand all your terminology. This is one of the keys to success in any field. This is the basis for many seemingly difficult terms. Study these roots. Make 3" x 5" flash cards to help you memorizse them and later do the same with your terminology.

4. Pay attention.

5. Make it a practice to read over the topic or chapter before going to your biology class.

6. Attend all classes and be an active listener. It is important to be alert and concentrate on what is said in class. Successful students take full and comprehensive notes, writing down about 66% of what is said in class, while failing students write half as much. It is most important to stay current. Do not allow yourself to miss classes and fall behind or the entire course will become an effort and a struggle for you.

7. After class go over the material as soon as possible and again 8 hours later. Studies have shown that you are more likely to remember the information later. Fill in all the missing words or incomplete explanations. Recite important concepts in your own words.

8. Always remember you have the right to ask questions before, during and after class. See your teachers during their office hours for help. Notice when you are beginning to get in trouble and seek help immediately.

9. Read and study all your textbook explanations. You may wish to use at least two or more books. These books are often available in the library. Each book has a different discussion and examples on your topic, and one of these is likely to be helpful to you.

10. Whenever possible explain aloud to another person what you are learning. Work with a classmate and explain terminology and concepts to each other.

11. Describe in your own words the similarities and differences between the different concepts you are learning. Do this aloud with someone else.

12. If biology is your most difficult subject, then always study it before all other subjects. You must study biology when you are most alert and fresh. Make sure to take 5 or 10 minute breaks every 2040 minutes in order to clear your mind.

13. Write up summary sheets of biology terminology and concepts and review often. The more you review the more you'll remember. Also visually picture the terms in your minds eye. Visualising is a powerful technique for remembering terms. Break words into small chunks and picture each chunk until you can recall it. Then put the chunks together. Remember, the knowledge of roots can be extremely helpful.

14. Making up mnemonics memory techniques may be fun as well as beneficial. For example, if you need to remember the 12 cranial nerves you can take the first letter of each nerve and make up a sentence where each word begins with the first letter of each nerves.

15. Create sample tests for yourself and test yourself often.

16. Give yourself timed tests similar to those you expect in class. Time yourself with a kitchen timer or an alarm. Practice, practice, practice.

17. Review the types of errors you make and types of questions that cause you difficulty. Give yourself more practice in these areas of difficulty.

18. If possible, have a friend or family member quiz you on your notes and text information. Done regularly this commits more information to longterm memory.

Good luck.

Double Fertilisation

2011-07-27T14:00:00.000+08:00

After landing on a receptive stigma, a pollen grain absorbs moisture and germinates; that is, it produces a pollen tube that extends down between the cells of the style toward the ovary.

The nucleus of the generative cell divides by mitosis and forms two sperm. Directed by a chemical attractant, possibly calcium, the tip of the pollen tube enters the ovary, probes through the micropyle (a gap in the integuments of the ovule), and discharges its two sperm near or within the embryo sac.

The events that follow are a distinctive feature of the angiosperm life cycle. One sperm fertilises the egg to form the zygote. The other sperm combines with the two polar nuclei to form a triploid (3n) nucleus in the centre of the large central cell of the embryo sac. This large cell will give rise to the endosperm, a food–storing tissue of the seed. The union of two sperm cells with different nuclei of the embryo sac is called double fertilisation. Double fertilisation ensures that the endosperm will develop only in ovules where the egg has been fertilised, thereby preventing angiosperms from squandering nutrients.

The tissues surrounding the embryo sac have prevented researchers from being able to directly observe fertilisation in plants grown under normal conditions. Recently, however, scientists have isolated sperm from germinated pollen grains and eggs from embryo sacs and have observed the merging of plant gametes in vitro (in an artificial environment). The first cellular event that takes place after gamete fusion is an increase in the cytoplasmic calcium (Ca2+) levels of the egg, as also occurs during animal gamete fusion. Another similarity to animals is the establishment of a block to polyspermy, the fertilisation of an egg by more than one sperm cell. Thus, maize (Zea mays ) sperm cannot fuse with zygotes in vitro. In maize, this barrier to polyspermy is established as early as 45 seconds after the initial sperm fusion with the egg.

From Ovule to Seed
After double fertilisation, each ovule develops into a seed, and the ovary develops into a fruit enclosing the seed(s). As the embryo develops from the zygote, the seed stockpiles proteins, oils, and starch to varying extents, depending on the species. This is why seeds are such major sugar sinks. Initially, these nutrients are stored in the endosperm, but later in seed development in many species, the storage function of the endosperm is more or less taken over by the swelling cotyledons of the embryo.

Endosperm Development
Endosperm development usually precedes embryo development. After double fertilisation, the triploid nucleus of the ovule’s central cell divides, forming a multinucleate “supercell” having a milky consistency. This liquid mass, the endosperm, becomes multicellular when cytokinesis partitions the cytoplasm by forming membranes between the nuclei. Eventually, these “naked” cells produce cell walls, and the endosperm becomes solid. Coconut “milk” is an example of liquid endosperm; coconut “meat” is an example of solid endosperm. The white fluffy part of popcorn is also solid endosperm.

In grains and most other monocots, as well as many eudicots, the endosperm stores nutrients that can be used by the seedling after germination. In other eudicots (including bean seeds), the food reserves of the endosperm are completely exported to the cotyledons before the seed completes its development; consequently, the mature seed lacks endosperm.

Digestive System

2011-07-27T13:52:00.000+08:00

Each organ of the mammalian digestive system has specialised food–processing functions.

The general principles of food processing are similar for a diversity of animals, so we can use the digestive system of mammals as a representative example. The mammalian digestive system consists of the alimentary canal and various accessory glands that secrete digestive juices into the canal through ducts.

After food is chewed and swallowed, it takes only 5–10 seconds for it to pass down the oesophagus and into the stomach, where it spends 2–6 hours being partially digested. Final digestion and nutrient absorption occur in the small intestine over a period of 5–6 hours. In 12–24 hours, any undigested material passes through the large intestine, and faeces are expelled through the anus.

The general principles of food processing are similar for a diversity of animals, so we can use the digestive system of mammals as a representative example. The mammalian digestive system consists of the alimentary canal and various accessory glands that secrete digestive juices into the canal through ducts.

Peristalsis, rhythmic waves of contraction by smooth muscles in the wall of the canal, pushes the food along the tract. At some of the junctions between specialised segments of the digestive tube, the muscular layer is modified into ringlike valves called sphincters, which close off the tube like drawstrings, regulating the passage of material between chambers of the canal. The accessory glands of the mammalian digestive system are three pairs of salivary glands, the pancreas, the liver and the gallbladder, which stores a digestive juice.

Using the human digestive system as a model, let′s now follow a meal through the alimentary canal, examining in more detail what happens to the food in each of the processing stations along the way.

The Oral Cavity, Pharynx, and Oesophagus
Both physical and chemical digestion of food begin in the mouth. During chewing, teeth of various shapes cut, smash, and grind food, making it easier to swallow and increasing its surface area. The presence of food in the oral cavity triggers a nervous reflex that causes the salivary glands to deliver saliva through ducts to the oral cavity. Even before food is actually in the mouth, salivation may occur in anticipation because of learned associations between eating and the time of day, cooking odours, or other stimuli. Humans secrete more than a liter of saliva each day.

Saliva contains a slippery glycoprotein (carbohydrate–protein complex) called mucin, which protects the lining of the mouth from abrasion and lubricates food for easier swallowing. Saliva also contains buffers that help prevent tooth decay by neutralising acid in the mouth. Antibacterial agents in saliva kill many of the bacteria that enter the mouth with food.

Chemical digestion of carbohydrates, a main source of chemical energy, begins in the oral cavity. Saliva contains salivary amylase, an enzyme that hydrolyses starch (a glucose polymer from plants) and glycogen (a glucose polymer from animals). The main products of this enzyme′s action are smaller polysaccharides and the disaccharide maltose.

The tongue tastes food, manipulates it during chewing, and helps shape the food into a ball called a bolus. During swallowing, the tongue pushes a bolus to the back of the oral cavity and into the pharynx.

The region we call our throat is the pharynx, a junction that opens to both the oesophagus and the windpipe (trachea). When we swallow, the top of the windpipe moves up so that its opening, the glottis, is blocked by a cartilaginous flap, the epiglottis. You can see this motion in the bobbing of the “Adam′s apple” during swallowing. This tightly controlled mechanism normally ensures that a bolus is guided into the entrance of the oesophagus.

Food or liquids may go “down the wrong pipe” because the swallowing reflex didn′t close the opening of the windpipe in time. The resulting blockage of airflow (choking) stimulates vigorous coughing, which usually expels the material. If it is not expelled quickly, the lack of airflow to the lungs can be fatal.

The oesophagus conducts food from the pharynx down to the stomach by peristalsis. The muscles at the very top of the oesophagus are striated (voluntary). Thus, the act of swallowing begins voluntarily, but then the involuntary waves of contraction by smooth muscles in the rest of the esophagus take over.

The Stomach
The stomach stores food and performs preliminary steps of digestion. This large organ is located in the upper abdominal cavity, just below the diaphragm. With accordionlike folds and a very elastic wall, the stomach can stretch to accommodate about 2 L of food and fluid. It is because the stomach can store an entire meal that we do not need to eat constantly. Besides storing food, the stomach performs important digestive functions: It secretes a digestive fluid called gastric juice and mixes this secretion with the food by the churning action of the smooth muscles in the stomach wall.

Gastric juice is secreted by the epithelium lining numerous deep pits in the stomach wall. With a high concentration of hydrochloric acid, gastric juice has a pH of about 2—acidic enough to dissolve iron nails. One function of the acid is to disrupt the extracellular matrix that binds cells together in meat and plant material. The acid also kills most bacteria that are swallowed with food. Also present in gastric juice is pepsin, an enzyme that begins the hydrolysis of proteins. Pepsin breaks peptide bonds adjacent to specific amino acids, cleaving proteins into smaller polypeptides, which are later digested completely to amino acids in the small intestine. Pepsin is one of the few enzymes that works best in a strongly acidic environment. The low pH of gastric juice denatures (unfolds) the proteins in food, increasing exposure of their peptide bonds to pepsin.

What prevents pepsin from destroying the cells of the stomach wall? First, pepsin is secreted in an inactive form called pepsinogen by specialised cells called chief cells located in gastric pits.

Other cells, called parietal cells, also in the pits, secrete hydrochloric acid. The acid converts pepsinogen to active pepsin by removing a small portion of the molecule and exposing its active site. Because different cells secrete the acid and pepsinogen, the two ingredients do not mix—and pepsinogen is not activated—until they enter the lumen (cavity) of the stomach. Activation of pepsinogen is an example of positive feedback: Once some pepsinogen is activated by acid, activation occurs at an increasingly rapid rate because pepsin itself can activate additional molecules of pepsinogen. Many other digestive enzymes are also secreted in inactive forms that become active within the lumen of the digestive tract.

The stomach′s second defense against self–digestion is a coating of mucus, secreted by the epithelial cells of the stomach lining. Still, the epithelium is constantly eroded, and mitosis generates enough cells to completely replace the stomach lining every three days. Gastric ulcers, lesions in this lining, are caused mainly by the acid–tolerant bacterium Helicobacter pylori

Though treatable with antibiotics, gastric ulcers may worsen if pepsin and acid destroy the lining faster than it can regenerate.

About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles. You may feel hunger pangs when your empty stomach churns. (Sensations of hunger are also associated with brain centres that monitor the blood′s nutritional status and levels of the appetite–controlling hormones discussed earlier in this chapter.) As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient–rich broth known as acid chyme.

Most of the time, the stomach is closed off at both ends. The opening from the oesophagus to the stomach, the cardiac orifice, normally dilates only when a bolus arrives. The occasional backflow of acid chyme from the stomach into the lower end of the oesophagus causes heartburn. (If backflow is a persistent problem, an ulcer may develop in the oesophagus.) At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine, one squirt at a time. It takes about 2 to 6 hours after a meal for the stomach to empty in this way.

The Small Intestine
With a length of more than 6 m in humans, the small intestine is the longest section of the alimentary canal (its name refers to its small diameter, compared with that of the large intestine). Most of the enzymatic hydrolysis of food macromolecules and most of the absorption of nutrients into the blood occur in the small intestine.

Most digestion is completed early in this journey, while the chyme is still in the duodenum. The remaining regions of the small intestine, called the jejunum and ileum, function mainly in the absorption of nutrients and water

Absorption of Nutrients
To enter the body, nutrients in the lumen must cross the lining of the digestive tract. A few nutrients are absorbed in the stomach and large intestine, but most absorption occurs in the small intestine. This organ has a huge surface area—300 m2, roughly the size of a tennis court. Large circular folds in the lining bear fingerlike projections called villi, and each epithelial cell of a villus has many microscopic appendages called microvilli that are exposed to the intestinal lumen

(The microvilli′s shape is the basis of the term brush border for the intestinal epithelium.) This enormous microvillar surface is an adaptation that greatly increases the rate of nutrient absorption.

Penetrating the core of each villus is a net of microscopic blood vessels (capillaries) and a small vessel of the lymphatic system called a lacteal. (In addition to their circulatory system, vertebrates have an associated network of vessels—the lymphatic system—that carries a clear fluid called lymph. Nutrients are absorbed across the intestinal epithelium and then across the unicellular epithelium of the capillaries or lacteals. Only these two single layers of epithelial cells separate nutrients in the lumen of the intestine from the bloodstream.

In some cases, transport of nutrients across the epithelial cells is passive. The simple sugar fructose, for example, apparently moves by diffusion down its concentration gradient from the lumen of the intestine into the epithelial cells and then into capillaries. Other nutrients, including amino acids, small peptides, vitamins, and glucose and several other simple sugars, are pumped against concentration gradients by the epithelial membranes. This active transport allows the intestine to absorb a much higher proportion of the nutrients in the intestine than would be possible with passive diffusion.

Amino acids and sugars pass through the epithelium, enter capillaries, and are carried away from the intestine by the bloodstream. After glycerol and fatty acids are absorbed by epithelial cells, they are recombined into fats within those cells. The fats are then mixed with cholesterol and coated with proteins, forming small globules called chylomicrons, most of which are transported by exocytosis out of the epithelial cells and into lacteals

The lacteals converge into the larger vessels of the lymphatic system. Lymph, containing chylomicrons, eventually drains from the lymphatic system into large veins that return blood to the heart.

In contrast to the lacteals, the capillaries and veins that drain nutrients away from the villi all converge into the hepatic portal vein, a blood vessel that leads directly to the liver. This ensures that the liver—which has the metabolic versatility to interconvert various organic molecules—has first access to amino acids and sugars absorbed after a meal is digested. Therefore, blood that leaves the liver may have a very different balance of these nutrients than the blood that entered via the hepatic portal vein. For example, the liver helps regulate the level of glucose molecules in the blood, and blood exiting the liver usually has a glucose concentration very close to 0.1%, regardless of the carbohydrate content of a meal (see Figure 41.3). From the liver, blood travels to the heart, which pumps the blood and the nutrients it contains to all parts of the body.

The large intestine or colon, is connected to the small intestine at a T–shaped junction, where a sphincter (a muscular valve) controls the movement of material. One arm of the T is a pouch called the caecum. Compared to many other mammals, humans have a relatively small caecum. The human cecum has a fingerlike extension, the appendix, which is dispensable. (Lymphoid tissue in the appendix makes a minor contribution to body defense.) The main branch of the human colon is about 1.5 m long.

A major function of the colon is to recover water that has entered the alimentary canal as the solvent of the various digestive juices. About 7 L of fluid are secreted into the lumen of the digestive tract each day, which is much more liquid than most people drink. Most of this water is reabsorbed when nutrients are absorbed in the small intestine. The colon reclaims much of the remaining water that was not absorbed in the small intestine. Together, the small intestine and colon reabsorb about 90% of the water that enters the alimentary canal.

The wastes of the digestive tract, the faeces, become more solid as they are moved along the colon by peristalsis. The movement is sluggish, and it generally takes about 12 to 24 hours for material to travel the length of the organ. If the lining of the colon is irritated—by a viral or bacterial infection, for instance—less water than normal may be reabsorbed, resulting in diarrhea. The opposite problem, constipation, occurs when peristalsis moves the feces along the colon too slowly. An excess of water is reabsorbed, and the faeces become compacted.

Living in the large intestine is a rich flora of mostly harmless bacteria. One of the common inhabitants of the human colon is Escherichia coli, a favourite research organism of molecular biologists. The presence of Escherica coli in lakes and streams is an indication of contamination by untreated sewage. Intestinal bacteria live on unabsorbed organic material. As by–products of their metabolism, many colon bacteria generate gases, including methane and hydrogen sulfide. Some of the bacteria produce vitamins, including biotin, folic acid, vitamin K, and several B vitamins. These vitamins, absorbed into the blood, supplement our dietary intake of vitamins.

Faeces contain masses of bacteria, as well as cellulose and other undigested materials. Although cellulose fibers have no caloric value to humans, their presence in the diet helps move food along the digestive tract.

The terminal portion of the colon is called the rectum, where faeces are stored until they can be eliminated. Between the rectum and the anus are two sphincters, one involuntary and the other voluntary. One or more times each day, strong contractions of the colon create an urge to defecate.

A hole in the heart

2011-07-21T23:27:00.001+08:00

We always talk about conditions affecting the heart later in life such as hypertension, coronary heart disease and heart failure. We don't talk much of any conditions of the heart which are present at birth, known as congenital heart disease or defects.

Congenital heart disease, also abbreviated to CHD and not to be confused with coronary heart disease, is a type of defect or malformation in one or more structures of the heart or blood vessels that occurs before birth. These defects happen as the foetus is developing.

CHD is more common than one thinks, occurring around 8 to 10 out of every 1,000 births. The cause is unknown in the majority of cases although certain conditions or factors can predispose a child to being born with CHD. They include genetic or chromosomal abnormalities in the child such as Down's Syndrome, viral infections in the mother during pregnancy such Rubella, and consumption of certain drugs or alcohol by the mother during pregnancy.

There are many different types of CHD and they range from a mild form that can go undetected until much later in life to the very severe where the baby is cyanosed - bluish discolouration of the lips and face because of lack of oxygen in the blood - within days of being born.

Let us just limit the discussion here to atrial and ventricular septal defects, known as ASD and VSD respectively. In layman's term, they are also known as hole-in-the-heart.

You all knoe that the heart is divided into four chambers - two on the left where blood rich in oxygen from the lungs passes through to get to the body - and two on the right where blood lacking in oxygen returning from the body goes to before it gets back to the lungs.

It is vital that the wall separating the two sides called the septum is intact. Any breach in the wall will mean that blood with different oxygen concentrations are mixed together. ASD is when the breach is in the septum between the two atria and likewise, VSD denotes a defect in the ventricular septum.

This may not be a big problem in the beginning as the left chambers which have a higher pressure system than the right will direct blood to the right chambers via the hole or defect in the wall. However, as the pressure rises in the right chambers through the years because of constant flow of high pressure from the left, it can damage the lung causing pulmonary hypertension.

When it comes to a point where both sides have the same blood pressure level, there is then a free mixing of high and low oxygenated blood on both sides resulting in body tissues being compromised of good oxygenation. The person will be cyanosed and breathless and may also have symptoms of heart failure.

Of course, that is the extreme end of the spectrum. For most with ASD or VSD, they are fairly asymptomatic and the condition only gets discovered during a routine medical examination when a murmur - a characteristic sound heard by using a stethoscope placed on the chest over the heart - is detected. The definitive test is an echocardiogram which is an ultrasound scan test of the heart.

When the septal defect is small the doctor will usually advise the person concerned to come back for a checkup every year or so. No regular medication is needed.

He will be advised to take antibiotics as a preventative measure against bacterial infection affecting the heart (endocarditis) if he is going to have a dental procedure or any procedure that may cause bleeding.

If the defect is big from the echocardiogram, then an interventional procedure or surgery to close the hole has to be considered.

If you are a parent and you notice the following in your child - cyanosis of the skin, lips and fingernails, poor weight gain, fast breathing, recurrent lung infections and inability to exercise well, it is suggested that you bring your child to the attention of your doctor or paediatrician. There is a possibility that he or she has a congenital heart disease.

Photosynthesis (SPM Level)

2011-07-19T00:20:00.002+08:00

Photosynthesis – takes place in the chloroplast
There two main stages : light reaction and dark reaction
Light reaction occurs only in the presence of light. Dark reaction occurs during day and night.
Light reaction - occurs in grana.
Chlorophyll captures light energy - excites the electrons to higher energy levels.
Electrons then leave the chlorophyll.
Light energy is also used to split water molecule into hydrogen ions and hydroxyl ions. This is known as photolysis of water.
Hydrogen ions combine with electrons released by chlorophyll to form hydrogen atoms.
The energy from excited electrons is used to form adenosine triphosphate (ATP).
At the same time, hydroxyl ion loses an electron to form hydroxyl group.
This electron is then received by chlorophyll.
The hydroxyl groups then combine to form water and gaseous oxygen.
Oxygen is released into the atmosphere and used for cellular respiration. The ATP molecules provide energy while the hydrogen atoms provide reducing power for the dark reaction.

Dark reaction - also known as Calvin cycle.
Occurs in stroma. Hydrogen atoms are used to fix carbon dioxide into glucose.
The glucose monomers then undergo condensation to form starch which is temporarily stored as starch grains in the chloroplasts.

Conclusion
Light reaction - occurs in the grana (contained chlorophyll) - takes place in the presence of sunlight and chlorophyll - chlorophyll absorbs light; then it becomes activated and this energy is used to :
i) produce energy in the form of – ATP (used for dark reaction)
ii) split up water molecules (photolysis) into hydroxyl ions(OH-) and hydrogen ions (H+) - oxygen is released; but hydrogen enters dark reaction.

Dark reaction (Light independent reaction) - takes place in the stroma -ATP combined with hydrogen atoms (from the light reaction) are used to reduce carbon dioxide to form glucose.

Glucose produced –
i) converted to starch (stored),
ii) transformed - sucrose ; transported to other parts
iii) synthesis of cellulose
iv) converted to a. acids and fatty acids

Spermatogenesis and Oogenesis

2011-06-26T23:11:00.002+08:00

Spermatogenesis
- takes place in seminiferous tubules
- 2 types of cells : Germinal epithelial cells & Sertoli cells

Stages
1. Germinal epithelial cells divide by mitosis - produce diploid(2n) spermatogonia
2. Spermatogonium grows - primary spermatocyte(2n)
3. Primary spermatocyte undergoes meiosis I - form 2 secondary spermatocytes(n)
4. Secondary spermatocytes divide through meiosis II - form 2 spermatids
5. Spermatids obtain nutrients from Sertoli cells - mature into sperms/spermatozoa

Oogenesis
- takes place in the ovaries
- form oocytes in the ovary of foetus (begins before birth)

Stages

1. Germinal epithilial cells multiply by mitosis - form oogonia/oogonium(2n)
2. Oogonium grows - form primary oocyte(2n)
3. Oocyte surrounded by follicle cells (follicle cell - nourishing the oocyte & secrete oestrogen)
4. Primary oocyte + follicle - Primary follicle
5. Feotus grows, primary oocytes undergo meiosis I but stops at Prophase 1.
6. During birth - 2 millions primary oocytes
7. At puberty - 400 000 primary oocytes
8. Every month, primary oocytes become active (meiosis) - only 1 primary follicle matures
9. Meiosis I forms 2 cells
i. First polar body - degenerates (Meiosis II may/may not occur)
ii. Secondary oocyte starts Meiosis II - until Metaphase II
10. Secondary oocyte + follicle = Secondary follicle
11. Secondary follicle matures into Graafian follicle
12. Ovarian wall ruptures - releases Secondary oocyte/Egg (ovulation process)
13. If a sperm penetrates the secondary oocyte, Meiosis II completes and form 2 haploid cells.
i. Ovum (n)
ii. Second polar body (smaller cell)
15. Nucles of sperm + nucles of ovum - zygote (2n/diploid)
16. Graafian follicle (left over in ovary) - forms corpus luteum
17. No pregnancy - corpus luteum degenerates (after 10 days)
18. Pregnancy occurs - corpus luteum secretes progesterone and oestrogen until placenta takes over the tasks (3 months)

My name is cholesterol

2011-05-29T17:13:00.000+08:00

CHOLESTEROL is a type of fat that is a normal component of most body tissues, and is required for good health. Yet, high levels can increase the risk of developing diseases (eg heart disease).

High cholesterol levels are asymptomatic, and in many cases, the first sign of any problem is a serious health issue. To help reduce the risk of this occuring, cholesterol levels are measured by a simple blood test. Your healthcare professional can organise this for you, along with other measurements of your cardiovascular health, such as blood pressure testing.

Cholesterol is transported through the blood stream in particles known as lipoproteins. The two most important varieties of lipoproteins to be aware of are low-density lipoproteins (LDL) and high-density lipoproteins (HDL).

High levels of LDL-cholesterol can lead to fatty deposits in the artery walls, referred to as atherosclerosis, or “hardening of the arteries”. Atherosclerosis makes the blood vessels narrower and stiffer, and consequently, increases the risk of heart disease and stroke.

This form of cholesterol is sometimes referred to as “bad” cholesterol.

High-density lipoproteins (HDL-cholesterol) help to reduce the risk of heart disease as they have the ability to help remove excess cholesterol from the arteries and other parts of the body. For this reason, they are sometimes referred to as “good” cholesterol.

The narrowing of the arteries associated with high cholesterol levels can sometimes cause symptoms that include chest pain (angina), or leg pain (intermittent claudication), especially with exercise.

High production of cholesterol by the liver may contribute to the development of gallstones, symptoms of which include episodic abdominal and back pain, especially after consumption of fatty foods.

Cholesterol levels in the blood depend on dietary factors and the amount of cholesterol manufactured by the body. High consumption of saturated fat, trans fat and cholesterol in foods may make your total cholesterol and LDL cholesterol levels rise.

Genetics also play a role in some people with high cholesterol. Your genes will partly determine how much cholesterol you naturally produce. Familial hypercholesterolaemia is more likely to be present in people who experience a heart attack at an early age or who have a family member who had a heart attack at an early age.

Being overweight contributes to increased LDL-cholesterol.

Other blood markers that may be associated with high cholesterol levels and are also risk factors for cardiovascular disease include high levels of a compound called homocysteine and high blood levels of triglycerides (fats).

Free radical damage to cholesterol molecules is believed to increase their ability to damage blood vessels.

Remember that cholesterol is not a disease in itself, but an indicator of the risk of developing heart disease. Your healthcare professional will consider your cholesterol level in the context of other risk factors, such as your family history, blood pressure, level of physical activity, and whether you are diabetic or smoke cigarettes.

Measures you can take to help reduce cholesterol levels include:

● To help maintain healthy cholesterol levels, reduce the quantity of cholesterol and saturated and trans fats in your diet. This involves avoiding animal fats (meat and full-fat dairy products) and sources of hidden fat such as pastries and pies.

● At the same time, increase the amount of fish in your diet (but not deep fried fish), and eat more fruit, vegetables and whole grains.

● A diet high in soluble fibre is highly recommended in order to promote the excretion of cholesterol. Good sources include legumes, oats and psyllium.

● Eating moderate amounts of foods that contain monounsaturated fats may support the management of healthy normal cholesterol levels. Important foods to include in your diet include nuts (especially walnuts), seeds and olive oil.

● Garlic and onion have cholesterol-lowering properties and are valuable additions to your diet.

● Limit your alcohol consumption to one to two standard drinks per day, and avoid binge drinking.

● Quit smoking. Cigarette smoking significantly increases the risk of cardiovascular disease and other health problems, and can exacerbate the negative effects of high cholesterol levels.

● Regular aerobic exercise can be of benefit to those with high cholesterol levels. Aim for at least 30 minutes of brisk walking per day. Always seek the advice of your healthcare professional before commencing an exercise programme.

● If you are overweight, talk to your healthcare professional about ways to address this, as being overweight may contribute to raised LDL and triglyceride levels.

There are also certain natural alternatives you can consider:

● Plant sterols (also known as phytosterols) may help reduce LDL-cholesterol levels and assist in improving the LDL:HDL ratio to healthier levels. They work by lowering cholesterol absorption and reabsorption. Take a daily dose of 2-3 grams of plant sterols, as recommended by the National Heart Foundation of Australia. Choose a formula that also supplies a healthy dose of betacarotene, which may become depleted when taking plant sterols.

● Coenzyme Q10 helps maintain heart and artery health and inhibits the oxidation of LDL–cholesterol.

● Omega-3 fatty acids EPA and DHA from fish oil, may help decrease fat in the blood (triglycerides) in healthy people. Omega-3s also help to maintain the flexibility of the blood vessels, help maintain healthy heart rates, and help maintain healthy blood pressure.

● Antioxidant nutrients such as vitamin C and vitamin E help reduce the oxidation of LDL-cholesterol. Antioxidants are often taken with folic acid and the vitamins B6 and B12. Low intake of these B-group vitamins is a common cause of elevated plasma homocysteine.

● If you’re overweight, achieving a healthy body weight may aid the management of healthy cholesterol levels.

Your cholesterol level is only one aspect of your cardiovascular health profile and should be addressed in conjunction with other risk factors. Talk to your healthcare professional for more information.

Regulation of Kidney Function

2011-05-12T15:51:00.000+08:00

One of the most important aspects of the mammalian kidney is its ability to adjust both the volume and osmolarity of urine, depending on the animal′s water and salt balance and the rate of urea production. In situations of high salt intake and low water availability, a mammal can excrete urea and salt with minimal water loss in small volumes of hyperosmotic urine. But if salt is scarce and fluid intake is high, the kidney can get rid of the excess water with little salt loss by producing large volumes of hypoosmotic urine (as dilute as 70 mosm/L, compared to about 300 mosm/L for human blood). This versatility in osmoregulatory function is managed with a combination of nervous and hormonal controls.

One hormone that is important in regulating water balance is antidiuretic hormone (ADH).

ADH is produced in the hypothalamus of the brain and is stored in and released from the posterior pituitary gland, which is positioned just below the hypothalamus. Osmoreceptor cells in the hypothalamus monitor the osmolarity of blood; when it rises above a set point of 300 mosm/L (perhaps due to water loss from sweating or to ingestion of salty food), more ADH is released into the bloodstream and reaches the kidney. The main targets of ADH are the distal tubules and collecting ducts of the kidney, where the hormone increases the permeability of the epithelium to water. This amplifies water reabsorption, which reduces urine volume and helps prevent further increase of blood osmolarity above the set point. By negative feedback, the subsiding osmolarity of the blood reduces the activity of osmoreceptor cells in the hypothalamus, and less ADH is then secreted. But only the gain of additional water in food and drink can bring osmolarity all the way back down to 300 mosm/L.

Conversely, if a large intake of water has reduced blood osmolarity below the set point, very little ADH is released. This decreases the permeability of the distal tubules and collecting ducts, so water reabsorption is reduced, resulting in increased discharge of dilute urine. (Increased urination is called diuresis, and it is because ADH opposes this state that it is called anti diuretic hormone.) Alcohol can disturb water balance by inhibiting the release of ADH, causing excessive urinary water loss and dehydration (which may cause some of the symptoms of a hangover). Normally, blood osmolarity, ADH release, and water reabsorption in the kidney are all linked in a feedback loop that contributes to homeostasis.

A second regulatory mechanism involves a specialised tissue called the juxtaglomerular apparatus (JGA), located near the afferent arteriole that supplies blood to the glomerulus. When blood pressure or blood volume in the afferent arteriole drops (for instance, as a result of reduced salt intake or loss of blood), the enzyme renin initiates chemical reactions that convert a plasma protein called angiotensinogen to a peptide called angiotensin II. Functioning as a hormone, angiotensin II raises blood pressure by constricting arterioles, decreasing blood flow to many capillaries, including those of the kidney. Angiotensin II also stimulates the proximal tubules of the nephrons to reabsorb more NaCl and water. This reduces the amount of salt and water excreted in the urine and consequently raises blood volume and pressure. Another effect of angiotensin II is stimulation of the adrenal glands to release a hormone called aldosterone. This hormone acts on the nephrons′ distal tubules, making them reabsorb more sodium (Na+) and water and increasing blood volume and pressure. In summary, the renin–angiotensin–aldosterone system (RAAS) is part of a complex feedback circuit that functions in homeostasis. A drop in blood pressure and blood volume triggers renin release from the JGA. In turn, the rise in blood pressure and volume resulting from the various actions of angiotensin II and aldosterone reduce the release of renin.

The functions of ADH and the RAAS may seem to be redundant, but this is not the case. Both increase water reabsorption, but they counter different osmoregulatory problems. The release of ADH is a response to an increase in the osmolarity of the blood, as when the body is dehydrated from excessive water loss or inadequate intake of water. However, a situation that causes an excessive loss of both salt and body fluids—an injury, for example, or severe diarrhea—will reduce blood volume without increasing osmolarity. This will not induce a change in ADH release, but the RAAS will respond to the fall in blood volume and pressure by increasing water and Na+ reabsorption. ADH and the RAAS are partners in homeostasis; ADH alone would lower blood Na+ concentration by stimulating water reabsorption in the kidney, but the RAAS helps maintain balance by stimulating Na+ reabsorption.

Still another hormone, a peptide called atrial natriuretic factor (ANF), opposes the RAAS. The walls of the atria of the heart release ANF in response to an increase in blood volume and pressure. ANF inhibits the release of renin from the JGA, inhibits NaCl reabsorption by the collecting ducts, and reduces aldosterone release from the adrenal glands. These actions lower blood volume and pressure. Thus, ADH, the RAAS, and ANF provide an elaborate system of checks and balances that regulate the kidney′s ability to control the osmolarity, salt concentration, volume, and pressure of blood. The precise regulatory role of ANF is an area of active research.

Mammalian Kidney

2011-05-03T19:04:00.001+08:00

The excretory system of mammals centres on the kidneys, which are also the principal site of water balance and salt regulation. Mammals have a pair of kidneys. Each kidney, bean–shaped and about 10 cm long in humans, is supplied with blood by a renal artery and drained by a renal vein.

Blood flow through the kidneys is voluminous. In humans, the kidneys account for less than 1% of body weight, but they receive about 20% of resting cardiac output. Urine exits each kidney through a duct called the ureter, and both ureters drain into a common urinary bladder. During urination, urine is expelled from the urinary bladder through a tube called the urethra, which empties to the outside near the vagina in females or through the penis in males. Sphincter muscles near the junction of the urethra and the bladder, which are under nervous system control, regulate urination.

The mammalian kidney has two distinct regions, an outer renal cortex and an inner renal medulla. Packing both regions are microscopic excretory tubules and their associated blood vessels. The nephron—the functional unit of the vertebrate kidney—consists of a single long tubule and a ball of capillaries called the glomerulus. The blind end of the tubule forms a cup–shaped swelling, called Bowman′s capsule, which surrounds the glomerulus. Each human kidney contains about a million nephrons, with a total tubule length of 80 km.

Filtration of the Blood

Filtration occurs as blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman′s capsule. The porous capillaries, along with specialised cells of the capsule called podocytes, are permeable to water and small solutes but not to blood cells or large molecules such as plasma proteins. Filtration of small molecules is nonselective, and the filtrate in Bowman′s capsule contains salts, glucose, amino acids, and vitamins; nitrogenous wastes such as urea; and other small molecules—a mixture that mirrors the concentrations of these substances in blood plasma.

Pathway of the Filtrate

From Bowman′s capsule, the filtrate passes through three regions of the nephron: the proximal tubule; the loop of Henle, a hairpin turn with a descending limb and an ascending limb; and the distal tubule. The distal tubule empties into a collecting duct, which receives processed filtrate from many nephrons. This filtrate flows from the many collecting ducts of the kidney into the renal pelvis, which is drained by the ureter.

In the human kidney, approximately 80% of the nephrons, the cortical nephrons, have reduced loops of Henle and are almost entirely confined to the renal cortex. The other 20%, the juxtamedullary nephrons, have well–developed loops that extend deeply into the renal medulla. Only mammals and birds have juxtamedullary nephrons; the nephrons of other vertebrates lack loops of Henle. It is the juxtamedullary nephrons that enable mammals to produce urine that is hyperosmotic to body fluids, an adaptation that is extremely important for water conservation.

The nephron and the collecting duct are lined by a transport epithelium that processes the filtrate to form the urine. One of this epithelium′s most important tasks is reabsorption of solutes and water. Between 1,100 and 2,000 L of blood flows through a pair of human kidneys each day, a volume about 275 times the total volume of blood in the body. From this enormous traffic of blood, the nephrons and collecting ducts process about 180 L of initial filtrate, equivalent to two or three times the body weight of an average person. Of this, nearly all of the sugar, vitamins, and other organic nutrients and about 99% of the water are reabsorbed into the blood, leaving only about 1.5 L of urine to be voided.

Blood Vessels Associated with the Nephrons

Each nephron is supplied with blood by an afferent arteriole, a branch of the renal artery that subdivides into the capillaries of the glomerulus. The capillaries converge as they leave the glomerulus, forming an efferent arteriole. This vessel subdivides again, forming the peritubular capillaries, which surround the proximal and distal tubules. More capillaries extend downward and form the vasa recta, the capillaries that serve the loop of Henle. The vasa recta also form a loop, with descending and ascending vessels conveying blood in opposite directions.

Although the excretory tubules and their surrounding capillaries are closely associated, they do not exchange materials directly. The tubules and capillaries are immersed in interstitial fluid, through which various substances diffuse between the plasma within capillaries and the filtrate within the nephron tubule. This exchange is facilitated by the relative direction of blood flow and filtrate flow in the nephrons.

Secretion and reabsorption in the proximal tubule substantially alter the volume and composition of filtrate. For example, the cells of the transport epithelium help maintain a relatively constant pH in body fluids by the controlled secretion of H+. The cells also synthesise and secrete ammonia, which neutralises the acid and keeps the filtrate from becoming too acidic. The more acidic the filtrate, the more ammonia the cells produce and secrete, and the urine of a mammal usually contains some ammonia from this source (even though most nitrogenous waste is excreted as urea). The proximal tubules also reabsorb about 90% of the important buffer bicarbonate (HCO3−). Drugs and other poisons that have been processed in the liver pass from the peritubular capillaries into the interstitial fluid, and then are secreted across the epithelium of the proximal tubule into the nephron′s lumen. Conversely, valuable nutrients, including glucose, amino acids, and potassium (K+), are actively or passively transported from the filtrate to the interstitial fluid and then are moved into the peritubular capillaries.

One of the most important functions of the proximal tubule is reabsorption of most of the NaCl (salt) and water from the huge initial filtrate volume. Salt in the filtrate diffuses into the cells of the transport epithelium, and the membranes of the cells actively transport Na+ into the interstitial fluid. This transfer of positive charge is balanced by the passive transport of Cl− out of the tubule. As salt moves from the filtrate to the interstitial fluid, water follows by osmosis. The exterior side of the epithelium has a much smaller surface area than the side facing the lumen, minimizing leakage of salt and water back into the tubule. Instead, the salt and water now diffuse from the interstitial fluid into the peritubular capillaries.

Reabsorption of water continues as the filtrate moves into the descending limb of the loop of Henle. Here the transport epithelium is freely permeable to water but not very permeable to salt and other small solutes. For water to move out of the tubule by osmosis, the interstitial fluid bathing the tubule must be hyperosmotic to the filtrate. The osmolarity of the interstitial fluid does in fact become progressively greater from the outer cortex to the inner medulla of the kidney. Thus, filtrate moving downward from the cortex to the medulla within the descending limb of the loop of Henle continues to lose water to interstitial fluid of greater and greater osmolarity, which increases the solute concentration of the filtrate.

The filtrate reaches the tip of the loop, deep in the renal medulla in the case of juxtamedullary nephrons, then moves back to the cortex within the ascending limb. In contrast to the descending limb, the transport epithelium of the ascending limb is permeable to salt but not to water. The ascending limb has two specialized regions: a thin segment near the loop tip and a thick segment adjacent to the distal tubule. As filtrate ascends in the thin segment, NaCl, which became concentrated in the descending limb, diffuses out of the permeable tubule into the interstitial fluid. This movement increases the osmolarity of the interstitial fluid in the medulla. The exodus of salt from the filtrate continues in the thick segment of the ascending limb, but here the epithelium actively transports NaCl into the interstitial fluid. By losing salt without giving up water, the filtrate is progressively diluted as it moves up to the cortex in the ascending limb of the loop.

The distal tubule plays a key role in regulating the K+ and NaCl concentration of body fluids by varying the amount of the K+ that is secreted into the filtrate and the amount of NaCl reabsorbed from the filtrate. Like the proximal tubule, the distal tubule also contributes to pH regulation by the controlled secretion of H+ and reabsorption of bicarbonate (HCO3−).

The collecting duct carries the filtrate through the medulla to the renal pelvis. By actively reabsorbing NaCl, the transport epithelium of the collecting duct plays a large role in determining how much salt is actually excreted in the urine. Though its degree of permeability is under hormonal control, the epithelium is permeable to water. However, it is not permeable to salt or, in the renal cortex, to urea. Thus, as the collecting duct traverses the gradient of osmolarity in the kidney, the filtrate becomes increasingly concentrated as it loses more and more water by osmosis to the hyperosmotic interstitial fluid. In the inner medulla, the duct becomes permeable to urea. Because of the high urea concentration in the filtrate at this point, some urea diffuses out of the duct and into the interstitial fluid. Along with NaCl, this urea contributes to the high osmolarity of the interstitial fluid in the medulla. This high osmolarity enables the mammalian kidney to conserve water by excreting urine that is hyperosmotic to the general body fluids.

Weird Facts

2011-04-26T00:05:00.000+08:00

Can you feel the pulse in your wrist? For humans the normal pulse is 70 heartbeats per minute. Elephants have a slower pulse of 27 and for a canary it is 1000!

If all the blood vessels in your body were laid end to end, they would reach about 60,000 miles.

Abraham Lincoln probably had a medical condition called Marfans syndrome. Some of its symptoms are extremely long bones, curved spine, an arm span that is longer than the persons height, eye problems, heart problems and very little fat. It is a rare, inherited condition.

In one day your heart beats 100,000 times.

By the time you are 70 you will have easily drunk over 12,000 gallons of water.

Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!

Germs only cause disease, right? But a common bacterium, E. coli, found in the intestine helps us digest green vegetables and beans (also making gases - pew!). These same bacteria also make vitamin K, which causes blood to clot. If we didn't have these germs we would bleed to death whenever we got a small cut!

It takes more muscles to frown than it does to smile.

That dust on rugs and your furniture is not only dirt. It's mostly made of dead skin cells. Everybody loses millions of skin cells every day which fall on the floor and get kicked up to land on all the surfaces in a room. You could say, "That's me all over."

It takes food seven seconds to go from the mouth to the stomach via the oesophagus.

A human's small intestine is 6 meters long.

The human body is 75% water.

Your blood takes a very long trip through your body. If you could stretch out all of a human's blood vessels, they would be about 60,000 miles long. That's enough to go around the world twice.

The width of your armspan stretched out is the length of your whole body.

The average human dream lasts only 2 to 3 seconds.

The average American over fifty will have spent 5 years waiting in lines.

The farthest you can see with the naked eye is 2.4 million light years away! (140,000,000,000,000,000,000 miles.) That's the distance to the giant Andromeda Galaxy. You can see it easily as a dim, large gray "cloud" almost directly overhead in a clear night sky.

The average person has at least seven dreams a night.

Your brain is move active and thinks more at night than during the day.

Your brain is 80% water.

85% of the population can curl their tongue into a tube.

Your tongue has 3,000 taste buds.

Your forearm (from inside of elbow to inside of wrist) is the same length as your foot.

A sneeze travels at over 100 miles per hour. Gesundheit!

Your thigh bone is stronger than concrete.

Your fingernails grow almost four times as fast as your toenails.

You blink your eyes over 10,000,000 a year.
There were about 300 bones in your body when you were born, but by the time you reach adulthood you only have 206.

Nucleic Acids

2011-04-24T22:53:00.001+08:00

If the primary structure of polypeptides determines the conformation of a protein, what determines primary structure? The amino acid sequence of a polypeptide is programmed by a unit of inheritance known as a gene. Genes consist of DNA, which is a polymer belonging to the class of compounds known as nucleic acids.

The Roles of Nucleic Acids

There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) . These are the molecules that enable living organisms to reproduce their complex components from one generation to the next. Unique among molecules, DNA provides directions for its own replication. DNA also directs RNA synthesis and, through RNA, controls protein synthesis.

The figure above shows DNA → RNA → protein: a diagrammatic overview of information flow in a cell. In a eukaryotic cell, DNA in the nucleus programs protein production in the cytoplasm by dictating the synthesis of messenger RNA (mRNA), which travels to the cytoplasm and binds to ribosomes. As a ribosome (greatly enlarged in this drawing) moves along the mRNA, the genetic message is translated into a polypeptide of specific amino acid sequence.

DNA is the genetic material that organisms inherit from their parents. Each chromosome contains one long DNA molecule, usually consisting of from several hundred to more than a thousand genes. When a cell reproduces itself by dividing, its DNA molecules are copied and passed along from one generation of cells to the next. Encoded in the structure of DNA is the information that programs all the cell’s activities. The DNA, however, is not directly involved in running the operations of the cell, any more than computer software by itself can print a bank statement or read the bar code on a box of cereal. Just as a printer is needed to print out a statement and a scanner is needed to read a bar code, proteins are required to implement genetic programs. The molecular hardware of the cell—the tools for most biological functions—consists of proteins. For example, the oxygen carrier in the blood is the protein haemoglobin, not the DNA that specifies its structure.

How does RNA, the other type of nucleic acid, fit into the flow of genetic information from DNA to proteins? Each gene along the length of a DNA molecule directs the synthesis of a type of RNA called messenger RNA (mRNA). The mRNA molecule then interacts with the cell’s protein–synthesizsng machinery to direct the production of a polypeptide. We can summarise the flow of genetic information as DNA → RNA → protein. The actual sites of protein synthesis are cellular structures called ribosomes. In a eukaryotic cell, ribosomes are located in the cytoplasm, but DNA resides in the nucleus. Messenger RNA conveys the genetic instructions for building proteins from the nucleus to the cytoplasm. Prokaryotic cells lack nuclei, but they still use RNA to send a message from the DNA to the ribosomes and other equipment of the cell that translate the coded information into amino acid sequences.

The Structure of Nucleic Acids

Nucleic acids are macromolecules that exist as polymers called polynucleotides.

The components of nucleic acids.

(a) A polynucleotide has a regular sugar–phosphate backbone with variable appendages, the four kinds of nitrogenous bases. RNA usually exists in the form of a single polynucleotide, like the one shown here. (

b) A nucleotide monomer is made up of three components: a nitrogenous base, a sugar, and a phosphate group, linked together as shown here. Without the phosphate group, the resulting structure is called a nucleoside.

(c) The components of the nucleoside include a nitrogenous base (either a purine or a pyrimidine) and a pentose sugar (either deoxyribose or ribose).

As indicated by the name, each polynucleotide consists of monomers called nucleotides . A nucleotide is itself composed of three parts: a nitrogenous base, a pentose (five–carbon sugar), and a phosphate group. The portion of this unit without the phosphate group is called a nucleoside.

The DNA double helix and its replication. The DNA molecule is usually double–stranded, with the sugar–phosphate backbone of the antiparallel polynucleotide strands (symbolized here by blue ribbons) on the outside of the helix. Holding the two strands together are pairs of nitrogenous bases attached to each other by hydrogen bonds. As illustrated here with symbolic shapes for the bases, adenine (A) can pair only with thymine (T), and guanine (G) can pair only with cytosine (C). When a cell prepares to divide, the two strands of the double helix separate, and each serves as a template for the precise ordering of nucleotides into new complementary strands (orange). Each DNA strand in this figure is the structural equivalent of the polynucleotide diagrammed below.

DNA double helix

The RNA molecules of cells consist of a single polynucleotide chain like the one shown in the figure above .In contrast, cellular DNA molecules have two polynucleotides that spiral around an imaginary axis, forming a double helix.

The figure above shows the DNA double helix and its replication. The DNA molecule is usually double–stranded, with the sugar–phosphate backbone of the antiparallel polynucleotide strands (symbolised here by blue ribbons) on the outside of the helix. Holding the two strands together are pairs of nitrogenous bases attached to each other by hydrogen bonds. As illustrated here with symbolic shapes for the bases, adenine (A) can pair only with thymine (T), and guanine (G) can pair only with cytosine (C). When a cell prepares to divide, the two strands of the double helix separate, and each serves as a template for the precise ordering of nucleotides into new complementary strands (orange). Each DNA strand in this figure is the structural equivalent of the polynucleotide in the diagram.

James Watson and Francis Crick, working at Cambridge University, first proposed the double helix as the three–dimensional structure of DNA in 1953. The two sugar–phosphate backbones run in opposite 5′ → 3′ directions from each other, an arrangement referred to as antiparallel, somewhat like a divided highway. The sugar–phosphate backbones are on the outside of the helix, and the nitrogenous bases are paired in the interior of the helix. The two polynucleotides, or strands, as they are called, are held together by hydrogen bonds between the paired bases and by van der Waals interactions between the stacked bases. Most DNA molecules are very long, with thousands or even millions of base pairs connecting the two chains. One long DNA double helix includes many genes, each one a particular segment of the molecule.

Only certain bases in the double helix are compatible with each other. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). If we were to read the sequence of bases along one strand as we traveled the length of the double helix, we would know the sequence of bases along the other strand. If a stretch of one strand has the base sequence 5′–AGGTCCG–3′, then the base–pairing rules tell us that the same stretch of the other strand must have the sequence 3′–TCCAGGC–5′. The two strands of the double helix are complementary, each the predictable counterpart of the other. It is this feature of DNA that makes possible the precise copying of genes that is responsible for inheritance. In preparation for cell division, each of the two strands of a DNA molecule serves as a template to order nucleotides into a new complementary strand. The result is two identical copies of the original double–stranded DNA molecule, which are then distributed to the two daughter cells. Thus, the structure of DNA accounts for its function in transmitting genetic information whenever a cell reproduces.

DNA and Proteins as Tape Measures of Evolution

We are accustomed to thinking of shared traits, such as hair and milk production in mammals, as evidence of shared ancestors. Because we now understand that DNA carries heritable information in the form of genes, we can see that genes and their products (proteins) document the hereditary background of an organism. The linear sequences of nucleotides in DNA molecules are passed from parents to offspring; these sequences determine the amino acid sequences of proteins. Siblings have greater similarity in their DNA and proteins than do unrelated individuals of the same species. If the evolutionary view of life is valid, we should be able to extend this concept of “molecular genealogy” to relationships between species: We should expect two species that appear to be closely related based on fossil and anatomical evidence to also share a greater proportion of their DNA and protein sequences than do more distantly related species. In fact, that is the case. For example, if we compare a polypeptide chain of human hemoglobin with the corresponding hemoglobin polypeptide in five other vertebrates, we find the following. In this chain of 146 amino acids, humans and gorillas differ in just 1 amino acid, humans and gibbons differ in 2 amino acids, and humans and rhesus monkeys differ in 8 amino acids. More distantly related species have chains that are less similar. Humans and mice differ in 27 amino acids, and humans and frogs differ in 67 amino acids. Molecular biology has added a new tape measure to the toolkit biologists use to assess evolutionary kinship.

How to study Biology and succeed

2011-04-14T16:33:00.000+08:00

There are no tricks or short-cuts when it comes to succeeding in Biology class. Biology is difficult and there is no substitute for hard work. But what is meant by "hard work"? One component is time spent on task. When we speak of time, we should consider both the quantity of time spent and the quality of time spent.

There is so much material to be understood that a substantial time commitment is required. There is time spent in class, but also time spent preparing for class, reading the assigned pages, upgrading notes, and studying for tests (which might cover as many as 15 chapters). Yet, a student can devote a lot of time to these activities and still do poorly in Biology. This is because the quality of time spent is also an important factor. Many students become discouraged when, though they spend hours and even days studying for tests, they still get unsatisfactory scores. Usually this occurs because what they do when they study is low-quality work.

What are some examples of low-quality work? One example would be reading the textbook just to get the reading assignment out of the way. A student who reads properly, on the other hand, reads with a critical eye, constantly asking him/herself questions like: "If I had to teach this to someone, could I do it?" or "What if this process where screwed up somehow; then how would the results differ?" or "The text's treatment of this topic differs from what I learned in lower secondary (or what I learned in class today); what question could I ask in class that might clear this up?"

Another example of low-quality work is going over and over your class notes. This is an activity that assumes one will be tested in a low-quality fashion, i.e. with test items that require you to do nothing but recall and repeat. This is a false assumption. You will be asked to integrate concepts from different classes, to apply the principles of biology covered in class to situations that were not covered in the class or text, to evaluate new situations in light of the material covered during the test unit. High-quality work entails preparing for such questions. Preparing entails organising the mass of new information in such a way that it helps you understand the way the concepts are related to each other.

A final example of low-quality work is coming to class regularly and just taking notes. Why is this low-quality work? Because many people go on auto-pilot when they takes notes. They switch off their brains and become passive sponges or tape recorders, assuming that later on, they will only need to act like a pair of speakers to play back what was written down. As in other things, your attendance at classes or tuitions can be either low-quality or high-quality. High-quality attendance entails being critical during the classes, asking questions like: "Why does it work that way?" or "How do we know that? What is the evidence?" "How does that relate to what the teacher said the other day about...?" There is a world of difference between questions such as those listed above and questions like: "Could you repeat that?" or "Could you spell that?" or "Do we have to know this for the test?" The answers to these questions might be important, but asking them does not indicate that critical thinking has been going on, as do the earlier questions.

As you can see, the successful student will necessarily have to work hard. The suggestions above are labour-intensive; they require more mental gymnastics. But just as a gymnast would be foolish to expect to succeed at a complex manoeuver on the first try at an important competition, as foolish would be a student who expected to pass tests requiring higher-order thought processes without first practicing these same processes.

Successful students take pains to carry out some sort of class follow-up activity. For many, this means rewriting their class notes. A lot of students find this activity to be very tedious. An alternative follow-up activity is a strategy known as Concept Mapping. Like rewriting notes, this is an activity that helps you reorganise the information in a way that conforms to your mental "landscape." Better than rewriting your notes, it helps you to discern the patterns and relationships between concepts. Much research supports the effectiveness of this strategy in helping students learn complex material. The process will be detailed in the presentation that accompanies this handout. Below is a summary of the steps in constructing a concept map, followed by guidelines to use in constructing the most helpful maps possible.

Steps in Making A Concept Map

1. Make a list of the concepts from the class.

2. Rank the concepts from most general to most specific.

3. Start each map at the center of the top of the page with the most general concept, which will generally be the chief topic of a particular topic. Below it, place the second-most general concept(s), etc...

4. Circle these two concepts and link them with a solid line.

5. Label the line with a linking phrase.

6. Work your way down the page, adding increasingly specific concepts and looking for crosslinks, which should be drawn with dashed lines.

7. Add details (examples).

8. Do a second version of the map with the goal being to add formerly unnoticed crosslinks and to organise the map so that it flows as logically and as clearly as possible.

Guidelines for the Most Helpful Maps

1. A typical 80-minute class should contain at least 20 (and not more than 45) concepts. Concepts are usually nouns.

2. Label ALL links and crosslinks with linking phrases. Links generally consist of verbs, but other words may be used where appropriate.

3. Circle the concepts, leave examples uncircled.

4. Each concept should only appear once in a given map. Redundancy of concepts usually indicates that you missed an important conceptual relationship.

5. Concept maps should flow down the page only.

6. Concept maps should NOT resemble flow charts or chronologically based outlines of the class. They should not be sentences with some words diagrammed. An important goal is to accurately relate as many concepts as possible using crosslinks. Maps with long strings of concepts or with several isolated and unlinked branches indicate misunderstanding of the goal of concept mapping.

Further Suggestions:

1. Attend ALL classes: This gives you a good idea of what the teacher(s) think most important. It also allows you to learn by hearing and seeing simultaneously -- much more effective than either one of these alone.

2. Make a regular appointment with your teacher to go over questions you have, or test your own understanding by explaining material back to him/her. It is always better not to be an anonymous face in a crowd -- get to know you teachers.

3. Come to class prepared by having outlined the assigned pages ahead of time. This will help you make more sense of the class as you listen to it and this, in turn, will help you to...

4. Engage your brain in the class. Don't allow yourself to become a note-taking automaton. Think! Be critical! Be skeptical! Ask questions! If you are shy, ask questions after class or during office hours.

5. Put proper closure on each class. Within 24 hours of each class -- the sooner the better -- (1) ask yourself what the class was about without using your notes, and (2) write your answer in the form of a concept map. This is the best time to spot points of confusion or discrepancies between text and notes, which you should write down and follow-up on. It is very important to spend time in this fashion if you are serious about succeeding in biology.

6. Pay attention to the figures in your text, especially the summary figures, like Fig. 17.26 in Campbell's Biology, 7th edition. Figures are expensive to produce and publishers try to use them sparingly in order to reinforce main points.

7. Budget your time. There is such a huge amount of material to be mastered that studying cannot be put off into an all-night cram session before tests. This is a time-tested recipe for failure; if not failure of the test itself, then failure to understand biology. Will you have a cumulative final exam? What is your plan for keeping material from the beginning of the semester fresh and in mind? You would be well-advised to have such a plan.

8. Don't be a hermit. Once you have studied a good bit on your own, get together with a few others who are interested in understanding biology in order to bounce questions off each other, compare concept maps, create sample test questions, explain concepts to each other, and to be able to answer your colleagues' questions regarding those same explanations.

9. Don't miss the forest for the trees. Concentrate on the concepts, not on the minutiae. You will not be asked to recall picky details or to memorise tables (like the genetic code). You will be asked to apply broad concepts to solve specific problems.

Good luck.

Fake Egg

2011-04-08T23:36:00.001+08:00

Fake eggs are still going strong in China. Danwei.org published a small report in 2004 and several blogs reported on fake eggs such as The Raw Feed and Chinaview (in 2007 and 2006), but a look at the stories from Chinese language sources show that the problem is still there, if not bigger than before.

The profit margin for fake eggs, estimated at USD$70 per day, is more than enough for the common Chinese to engage in the business and there’s nothing China’s poor won’t do to get ahead. The list of faulty (or deadly) products coming out of China is long and will continue to lengthen for some time to come. It’s simply a matter of economy and history.

A cursory search of Chinese language news sites brought up more than 8,000 hits for “man-made eggs” including numerous news reports, instructional videos and most galling of all, dozens of ads for training manuals for interested entrepreneurs

In order to tell the difference between man-made and natural eggs, the first method is to inspect the shell. Man-made eggshells are particularly shiny and if the egg is opened, the egg white is not as sticky as a natural egg and is easily mixed in with the egg yolk. There may also be a light chemical smell coming from the egg yolk/white, whereas natural eggs have a fresh smell.

Man-made eggshells are made from Calcium Carbonate. The egg whites and egg yolks are made from the following materials: Alginic Acid, Potassium Alum, Gelatin, Calcium Chloride (with water) and artificial colouring. If fake, the yolk will quickly break up when fried

Man-made eggs are manufactured with chemicals, most importantly through the calcification of Alginic Acid. Man-made eggs are basically solidified gel. Most of the ingredients are additives that are regulated under Chinese law. None of these additives have any health benefits; man-made eggs cannot be considered a viable alternative to natural eggs.

Many of the ingredients involved in the manufacture of man-made eggs come in industrial and commercial forms. Considering the extremely low cost price of man-made eggs, it is uncertain what form of these additives the manufacturers are using. Research has shown that long-term consumption of man-made eggs can lead to memory-loss and dementia.

Check out this Health News Sohu story written by a journalist for the Qilu Evening News in Shandong.

In this story, the journalist follows the trail of one of the ads to a man in Shandong who claims to be the “Father of Man-made eggs”. The man, never named, tells how he charges 800RMB (US$120) per student. In his classes, the “Father” teaches how to make the egg-shell (the most important part of the process) as well as the yolk and white. According to the report, the man has taught college graduates as well as peasants and enjoys a comfortable living — safe from the authorities or anyone else — teaching down and out Chinese how to make fake eggs and get rich.

Carbohydrates

2011-03-26T23:14:00.000+08:00

Carbohydrates include both sugars and the polymers of sugars. The simplest carbohydrates are the monosaccharides, or single sugars, also known as simple sugars. Disaccharides are double sugars, consisting of two monosaccharides joined by a condensation reaction. The carbohydrates that are macromolecules are polysaccharides, polymers composed of many sugar building blocks.

Sugars

Monosaccharides (from the Greek monos, single, and sacchar, sugar) generally have molecular formulas that are some multiple of the unit CH2O.

The structure and classification of some monosaccharides. Sugars may be aldoses (aldehyde sugars, top row) or ketoses (ketone sugars, bottom row), depending on the location of the carbonyl group (dark orange). Sugars are also classified according to the length of their carbon skeletons. A third point of variation is the spatial arrangement around asymmetric carbons (compare, for example, the purple portions of glucose and galactose).

Glucose, the most common monosaccharide, is of central importance in the chemistry of life. In the structure of glucose, we can see the trademarks of a sugar: The molecule has a carbonyl group and multiple hydroxyl groups (–OH). Depending on the location of the carbonyl group, a sugar is either an aldose (aldehyde sugar) or a ketose (ketone sugar). Glucose, for example, is an aldose; fructose, a structural isomer of glucose, is a ketose. (Most names for sugars end in –ose.) Another criterion for classifying sugars is the size of the carbon skeleton, which ranges from three to seven carbons long. Glucose, fructose, and other sugars that have six carbons are called hexoses. Trioses (three–carbon sugars) and pentoses (five–carbon sugars) are also common.

Still another source of diversity for simple sugars is in the spatial arrangement of their parts around asymmetric carbons. Glucose and galactose, for example, differ only in the placement of parts around one asymmetric carbon. What seems like a small difference is significant enough to give the two sugars distinctive shapes and behaviours.

Although it is convenient to draw glucose with a linear carbon skeleton, this representation is not completely accurate. In aqueous solutions, glucose molecules, as well as most other sugars, form rings.

Monosaccharides, particularly glucose, are major nutrients for cells. In the process known as cellular respiration, cells extract the energy stored in glucose molecules. Not only are simple sugar molecules a major fuel for cellular work, but their carbon skeletons serve as raw material for the synthesis of other types of small organic molecules, such as amino acids and fatty acids. Sugar molecules that are not immediately used in these ways are generally incorporated as monomers into disaccharides or polysaccharides.

A disaccharide consists of two monosaccharides joined by a glycosidic linkage , a covalent bond formed between two monosaccharides by a dehydration reaction. For example, maltose is a disaccharide formed by the linking of two molecules of glucose.

Also known as malt sugar, maltose is an ingredient used in brewing beer. The most prevalent disaccharide is sucrose, which is table sugar. Its two monomers are glucose and fructose. Plants generally transport carbohydrates from leaves to roots and other nonphotosynthetic organs in the form of sucrose. Lactose, the sugar present in milk, is another disaccharide, in this case a glucose molecule joined to a galactose molecule.

Polysaccharides

Polysaccharides are macromolecules, polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkages. Some polysaccharides serve as storage material, hydrolyzed as needed to provide sugar for cells. Other polysaccharides serve as building material for structures that protect the cell or the whole organism. The architecture and function of a polysaccharide are determined by its sugar monomers and by the positions of its glycosidic linkages.

Storage Polysaccharides

Starch , a storage polysaccharide of plants, is a polymer consisting entirely of glucose monomers. Most of these monomers are joined by 1–4 linkages (number 1 carbon to number 4 carbon), like the glucose units in maltose. The angle of these bonds makes the polymer helical. The simplest form of starch, amylose, is unbranched. Amylopectin, a more complex form of starch, is a branched polymer with 1–6 linkages at the branch points.

Plants store starch as granules within cellular structures called plastids, which include chloroplasts.

Synthesising starch enables the plant to stockpile surplus glucose. Because glucose is a major cellular fuel, starch represents stored energy. The sugar can later be withdrawn from this carbohydrate “bank” by hydrolysis, which breaks the bonds between the glucose monomers. Most animals, including humans, also have enzymes that can hydrolyse plant starch, making glucose available as a nutrient for cells. Potato tubers and grains—the fruits of wheat, corn, rice, and other grasses—are the major sources of starch in the human diet.

Animals store a polysaccharide called glycogen , a polymer of glucose that is like amylopectin but more extensively branched. Humans and other vertebrates store glycogen mainly in liver and muscle cells. Hydrolysis of glycogen in these cells releases glucose when the demand for sugar increases. This stored fuel cannot sustain an animal for long, however. In humans, for example, glycogen stores are depleted in about a day unless they are replenished by consumption of food.

Structural Polysaccharides

Organisms build strong materials from structural polysaccharides. For example, the polysaccharide called cellulose is a major component of the tough walls that enclose plant cells. On a global scale, plants produce almost 1011 (100 billion) tons of cellulose per year; it is the most abundant organic compound on Earth. Like starch, cellulose is a polymer of glucose, but the glycosidic linkages in these two polymers differ. The difference is based on the fact that there are actually two slightly different ring structures for glucose .

When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below or above the plane of the ring. These two ring forms for glucose are called alpha (α) and beta (β), respectively. In starch, all the glucose monomers are in the α configuration. In contrast, the glucose monomers of cellulose are all in the β configuration, making every other glucose monomer upside down with respect to its neighbours.

The differing glycosidic links in starch and cellulose give the two molecules distinct three–dimensional shapes. Whereas a starch molecule is mostly helical, a cellulose molecule is straight (and never branched), and its hydroxyl groups are free to hydrogen–bond with the hydroxyls of other cellulose molecules lying parallel to it. In plant cell walls, parallel cellulose molecules held together in this way are grouped into units called microfibrils.

These cable–like microfibrils are a strong building material for plants as well as for humans, who use wood, which is rich in cellulose, for lumber.

Enzymes that digest starch by hydrolysing its α linkages are unable to hydrolyze the β linkages of cellulose because of the distinctly different shapes of these two molecules. In fact, few organisms possess enzymes that can digest cellulose. Humans do not; the cellulose in our food passes through the digestive tract and is eliminated with the feces. Along the way, the cellulose abrades the wall of the digestive tract and stimulates the lining to secrete mucus, which aids in the smooth passage of food through the tract. Thus, although cellulose is not a nutrient for humans, it is an important part of a healthful diet. Most fresh fruits, vegetables, and whole grains are rich in cellulose. On food packages, “insoluble fiber” refers mainly to cellulose.

Some microbes can digest cellulose, breaking it down to glucose monomers. A cow harbors cellulose–digesting bacteria in the rumen, the first compartment in its stomach.

The bacteria hydrolyse the cellulose of hay and grass and convert the glucose to other nutrients that nourish the cow. Similarly, a termite, which is unable to digest cellulose by itself, has microbes living in its gut that can make a meal of wood. Some fungi can also digest cellulose, thereby helping recycle chemical elements within Earth’s ecosystems.

Another important structural polysaccharide is chitin , the carbohydrate used by arthropods (insects, spiders, crustaceans, and related animals) to build their exoskeletons.

An exoskeleton is a hard case that surrounds the soft parts of an animal. Pure chitin is leathery, but it becomes hardened when encrusted with calcium carbonate, a salt. Chitin is also found in many fungi, which use this polysaccharide rather than cellulose as the building material for their cell walls. Chitin is similar to cellulose, except that the glucose monomer of chitin has a nitrogen–containing appendage.

Learning from Mistakes

2011-03-23T15:12:00.002+08:00

One of the best ways to relieve stress is to learn from your mistakes. Unfortunately, it’s difficult to find the balance between seeing too many things as someone else’s fault and seeing too many things as your fault. And in both cases, rumination can take root and cause too much stress. But how can you learn from your mistakes if you don’t realise when you’ve made one?

There’s no easy answer on how to learn from your mistakes that will work every time, though chapters have been written about it in classic books like The Road Less Travelled, and opportunities to address the topic have been missed in others, like The Four Agreements. However, there are some strategies you can use to learn from your mistakes that will work in various situations most of the time. When you’re trying to learn from your mistakes, consider the following:

Reframe Your Mistakes

First, use reframing to stop thinking of your mistakes as failures. They can be more accurately described as opportunities for learning—people generally learn more from mistakes than they learn from successes. With each mistake, you can learn valuable information that can be used for future success.

Be Forgiving

Next, maintain perspective and don’t take mistakes too seriously. Blaming others for our mistakes can be a defense mechanism for those who are harsh with ourselves when we mess up—we stay in denial because we can’t take our own harsh self-condemnation. Be forgiving. Just changing your outlook on this can make it less threatening to recognise when you’re responsible or partially responsible for things going other than you’d planned. And that makes you more able to learn from your mistakes.

See What You Can Change

Rather than thinking of who is more responsible for a situation—you or another person—look at the situation as a whole in terms of what you can change. If you view taking responsibility through the lens of personal control—what can you change next time, what do you have control over?—makes it an empowering experience to learn from your mistakes.

Look Beyond

Look at other sides of the same situation. How do different people in the situation feel. How might things have gone differently if you’d made different choices? Look at the situation in different ways. Play with it. And see what you can learn for next time.

Ask Questions

Ask for impartial opinions. Have a few trusted friends who will tell you the truth, and who can see things from both sides, and ask them what they see. Sometimes we’re too close to a situation to make sense of it at first, but an observer who isn’t so emotionally attached, and who can deliver their opinion with love and tact, is what we need to help us learn from our mistakes.

Pat Yourself On The Back

Congratulate yourself for whatever growth you’ve gained from dealing with each difficult situation you encounter and each mistake you make. Remember that these things add value to life as much as the more pleasant experiences we all value. And be glad that you always have the opportunity to learn from your mistakes in one way or another.

Radioactive Effects on Human

2011-03-14T20:56:00.002+08:00

Radioactive pollution can be defined as the emission of high energy particles or radioactive substance into air, water or land due to human activities in the form of radioactive waste. Radioactive waste is usually the product of a nuclear process such as nuclear fission, which is extensively used in nuclear reactors, nuclear weapons and other nuclear fuel-cycles.

The radioactivity of nuclear waste diminishes with time. That means the waste needs to be isolated from the reach of living beings until it no longer pose a threat to living beings. This time period may take from days to months and to years depending upon the radioactive nature of the waste.

Radioactive pollution that is spread through the earth’s atmosphere is called “Fallout”. The atmospheric nuclear pollution become prominent during the World War 2 period when United States, Britain and Soviet Union started conducting nuclear tests in the atmosphere. The best example of fallout is the nuclear bomb attack on Hiroshima and Nagasaki, Japan in 1945 by United States of America during World War 2.

As a result of nuclear bomb attack, nearly 2,250,000 people had died as a result of long-term exposure to radiation from the bomb blast within 5 years of attack due to radiation effect and cancer.

In land and water, the major source of radioactive pollution remains with the nuclear fuel cycle. The nuclear fuel cycle is used in nuclear power plants, extraction and refinement of materials from nuclear substance to be used in nuclear reactors and nuclear weapons, where the contaminants are left behind after the useful material (Nuclear Isotope) is extracted.

The effects of radioactive pollution or exposure to nuclear radiations were first reported in early 20th century when people working in uranium mines suffered from skin burn and cancer. The effects vary from organism to organism and from level of radioactivity of nuclear isotopes. The radiations destroy the cells in human body and causes cancer.

Radioactive particles forms ions when it reacts with biological molecules. These ions then form free radicals which slowly and steadily start destroying proteins, membranes, and nucleic acids. A longer exposure to radioactive radiations can damage the DNA cells that results in cancer, genetic defects for the generations to come and even death.

Long Term Effects on Humans
Long after the acute effects of radiation have subsided, radiation damage continues to produce a wide range of physical problems. These effects- including leukemia, cancer, and many others- appear two, three, even ten years later.

Blood Disorders

According to Japanese data, there was an increase in anaemia among persons exposed to the bomb. In some cases, the decrease in white and red blood cells lasted for up to ten years after the bombing.

Cataracts

There was an increase in cataract rate of the survivors at Hiroshima and Nagasaki, who were partly shielded and suffered partial hair loss.

Malignant Tumors

All ionising radiation is carcinogenic, but some tumour types are more readily generated than others. A prevalent type is leukaemia. The cancer incidence among survivors of Hiroshima and Nagasaki is significantly larger than that of the general population, and a significant correlation between exposure level and degree of incidence has been reported for thyroid cancer, breast cancer, lung cancer, and cancer of the salivary gland. Often a decade or more passes before radiation-caused malignancies appear.

Keloids

Beginning in early 1946, scar tissue covering apparently healed burns began to swell and grow abnormally. Mounds of raised and twisted flesh, called keloids, were found in 50 to 60 percent of those burned by direct exposure to the heat rays within 1.2 miles of the hypocenter. Keloids are believed to be related to the effects of radiation.

The Skeletal System

2011-03-10T23:35:00.000+08:00

Newborn and Jaundice (Demam Kuning)

2011-03-07T00:23:00.001+08:00

A common condition in newborns, jaundice refers to the yellow colour of the skin and whites of the eyes caused by excess bilirubin in the blood. Bilirubin is produced by the normal breakdown of red blood cells.

Normally, bilirubin passes through the liver and is excreted as bile through the intestines. Jaundice occurs when bilirubin builds up faster than a newborn's liver can break it down and pass it from the body. Reasons for this include:

Newborns make more bilirubin than adults do since they have more turnover of red blood cells.
A newborn baby's still-developing liver may not yet be able to remove adequate bilirubin from the blood.
Too large an amount of bilirubin is reabsorbed from the intestines before the baby gets rid of it in the stool.

High levels of bilirubin — usually above 25 mg — can cause deafness, cerebral palsy, or other forms of brain damage in some babies. In less common cases, jaundice may indicate the presence of another condition, such as an infection or a thyroid problem. It is recommended that all infants should be examined for jaundice within a few days of birth.

Types of Jaundice

The most common types of jaundice are:

Physiological (normal) jaundice: occurring in most newborns, this mild jaundice is due to the immaturity of the baby's liver, which leads to a slow processing of bilirubin. It generally appears at 2 to 4 days of age and disappears by 1 to 2 weeks of age.
Jaundice of prematurity: occurs frequently in premature babies since they are even less ready to excrete bilirubin effectively. Jaundice in premature babies needs to be treated at a lower bilirubin level than in full term babies in order to avoid complications.
Breastfeeding jaundice: jaundice can occur when a breastfeeding baby is not getting enough breast milk because of difficulty with breastfeeding or because the mother's milk isn’t in yet. This is not caused by a problem with the breast milk itself, but by the baby not getting enough to drink.
Breast milk jaundice: in 1% to 2% of breastfed babies, jaundice may be caused by substances produced in their mother's breast milk that can cause the bilirubin level to rise. These can prevent the excretion of bilirubin through the intestines. It starts after the first 3 to 5 days and slowly improves over 3 to 12 weeks.
Blood group incompatibility (Rh or ABO problems): if a baby has a different blood type than the mother, the mother might produce antibodies that destroy the infant's red blood cells. This creates a sudden buildup of bilirubin in the baby's blood. Incompatibility jaundice can begin as early as the first day of life. Rh problems once caused the most severe form of jaundice, but now can be prevented with an injection of Rh immune globulin to the mother within 72 hours after delivery, which prevents her from forming antibodies that might endanger any subsequent babies.

Symptoms and Diagnosis

Jaundice usually appears around the second or third day of life. It begins at the head and progresses downward. A jaundiced baby's skin will usually appear yellow first on the face, followed by the chest and stomach, and finally, the legs. It can also cause the whites of an infant's eyes to appear yellow.

Since many babies are now released from the hospital at 1 or 2 days of life, it is best for the baby to be seen by a doctor within 1 to 2 days of leaving the hospital to check for jaundice. Parents should also keep an eye on their infants to detect jaundice.

If you notice your baby’s skin or eyes looking yellow you should contact your child's doctor to see if significant jaundice is present.

At the doctor's office, a small sample of your infant's blood can be tested to measure the bilirubin level. Some offices use a light meter to get an approximate measurement, and then if it is high, check a blood sample. The seriousness of the jaundice will vary based on how many hours old your child is and the presence of other medical conditions.

When to Call the Doctor

Your doctor should be called immediately if:

jaundice is noted during the first 24 hours of life
the jaundice is spreading or getting more intense
your baby develops a fever over 100° Fahrenheit (37.8° Celsius) rectally
if your child starts to look or act sick

Also call the doctor right away if the colour deepens, your baby is not feeding well, or if you feel your baby is sleepier than usual. It is difficult to tell how significant jaundice is just by looking at a baby, so any baby who has yellow eyes or skin should be checked by the doctor.

Treatments

In mild or moderate levels of jaundice, by 1 to 2 weeks of age the baby will take care of the excess bilirubin on its own. For high levels of jaundice, phototherapy — treatment with a special light that helps rid the body of the bilirubin by altering it or making it easier for your baby's liver to get rid of it — may be used.

More frequent feedings of breast milk or supplementing with formula to help infants pass the bilirubin in their stools may also be recommended. In rare cases, a blood exchange may be required to give a baby fresh blood and remove the bilirubin.

If your baby develops jaundice that seems to be from breast milk, your doctor may ask you to temporarily stop breastfeeding. During this time, you can pump your breasts so you can keep producing breast milk and you can start nursing again once the condition has cleared.

If the amount of bilirubin is high, your baby may be readmitted to the hospital for treatment. Once the bilirubin level drops and the treatment is stopped, it is unlikely that treatment for jaundice will need to be restarted.

Depression

2011-02-28T22:19:00.001+08:00

Simple Ways to Fight Depression

If you feel depressed, it's best to do something about it — depression doesn't just go away on its own. In addition to getting help from a doctor or therapist, here are few things you can do to feel better.

Exercise. Take a 15- to 30-minute brisk walk every day — or dance, jog, or bike if you prefer. People who are depressed may not feel much like being active. But make yourself do it anyway (ask a friend to exercise with you if you need to be motivated). Once you get in the exercise habit, it won't take long to notice a difference in your mood.

Nurture yourself with good nutrition. Depression can affect appetite. One person may not feel like eating at all, but another might overeat. If depression has affected your eating, you'll need to be extra mindful of getting the right nourishment. Proper nutrition can influence a person's mood and energy. So eat plenty of fruits and vegetables and get regular meals (even if you don't feel hungry, try to eat something light, like a piece of fruit, to keep you going).

Identify troubles, but don't dwell on them. Try to identify any situations that have contributed to your depression. When you know what's got you feeling blue and why, talk about it with a caring friend. Talking is a way to release the feelings and to receive some understanding. If there's no one to tell, pouring your heart out to a journal works just as well.

Once you air out these thoughts and feelings, turn your attention to something positive. Take action to solve problems. Ask for help if you need it. Feeling connected to friends and family can help relieve depression. (It may also help them feel there's something they can do instead of just watching you hurt.)

Express yourself. With depression, a person's creativity and sense of fun may seem blocked. Exercise your imagination (painting, drawing, doodling, sewing, writing, dancing, composing music, etc.) and you not only get those creative juices flowing, you also loosen up some positive emotions. Take time to play with a friend or a pet, or do something fun for yourself. Find something to laugh about — a funny movie, perhaps. Laughter helps lighten your mood.

Look on the bright side. Depression affects a person's thoughts, making everything seem dismal, negative, and hopeless. If depression has you noticing only the negative, make an effort to notice the good things in life. Try to notice one thing, then try to think of one more. Consider your strengths, gifts, or blessings. Most of all, don't forget to be patient with yourself. Depression takes time to heal.

IN and OUT

2011-02-28T21:55:00.001+08:00

PASSIVE TRANSPORT

Plasma membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells. Some substances can cross the plasma membrane without any input of energy by the cell. The movement of such substances across the membrane is known as passive transport.

The activities of a cell depend on the materials that enter and leave the cell.

To stay alive, a cell must exchange materials such as food, oxygen and wastes with its surroundings.

These materials must cross the plasma membrane.

Small molecules like water, oxygen and carbon dioxide can move in and out freely, since they can squeeze between the molecules of the membrane.

Large or charged molecules like proteins, sugars and ions cannot.

The plasma membrane is thus said to be partially permeable.

A selectively permeable membrane only allows certain molecules to pass through.

SIMPLE DIFFUSION

The simplest type of passive transport, diffusion does not require the cell to use energy. Only small molecules can cross the plasma membrane by simple diffusion.

Diffusion is the movement of molecules from an area of high concentration to one of low concentration.

This difference in the concentration of molecules across a space is called the concentration gradient.

Diffusion is driven by the kinetic energy of the molecules. Because of their KE, molecules are in constant motion. Diffusion occurs when molecules move randomly away from each other in a liquid or gas.

The rate of diffusion depends on the temperature, size and the type of molecules that are diffusing.

Molecules diffuse faster at higher temperatures than at lower temperatures, and smaller molecules diffuse faster than large molecules.

Most transport of materials into and out of cells occurs by diffusion.

The concentration gradient is the difference between the concentration of a solute in one place and its concentration in an adjacent area.

Diffusion always occurs down a concentration gradient, i.e. from the area of higher concentration to the area of lower concentration.

When molecules are dispersed evenly, there is no longer any diffusion because there is no longer a concentration gradient.
Diffusion will eventually cause the concentration of molecules to be the same throughout the space the molecules occupy, when they will be in equilibrium.

OSMOSIS

Osmosis is “The process by which water molecules diffuse across a partially permeable membrane from a region of higher water potential/higher water concentration to a region of lower water potential/concentration”

Water moves by diffusion, like any other molecule, from a region of high concentration to one of low concentration, i.e. down its concentration gradient. Confusion occurs because ‘concentration’ normally refers to the solute concentration, whereas, in this case, we are referring to the solvent concentration.

For this reason, the use of the term ‘water potential/water concentration' is essential; water then simply moves ‘down the water potential gradient’ – easy!

The water potential of pure water is zero (0), so, since a solution must always be less than 100% pure water, all solutions (and cells) have a negative (-) water potential.

Insoluble molecules do not affect the solute potential (obviously), so have no osmotic effect. Such molecules are used for storage – starch, lipids, and very large proteins (albumin).

Water potential is actually a pressure, and is measured in Pascals (Pa), but since these are so small the normal unit is the kilo Pascal (kPa). Typical plant values are -200 to -2000kPa.

Plants have a cell wall which normally presses on the cell membrane, giving us the pressure potential (Ψp). Since this opposes the tendency of the cell to expand due to osmosis, it therefore follows that the pressure potential (Ψp) is always positive.

Since animals have no cell wall, and so no pressure potential, the solute potential and the water potential must be the same:

Similar logic shows that the water potential of every cell in an animals’ body must be the same, since they are all in contact with blood, and thus in equilibrium (‘two values that are equal to a third value, must be equal to each other’)

When a plant cell is turgid (its normal state), the net movement of water into and out of the cell is zero. Thus:

Note that calculations on this will not be set in the exam.

The net direction of osmosis depends on the relative concentration of solutes on the two sides of the cell membrane.
In a hypertonic solution, the concentration of solutes in the solution is higher and so it has a lower (i.e. more negative) water potential (Ψw). Therefore, when placed in a hypertonic solution, water leaves the cell by osmosis, until equilibrium is established.

If the cell loses too much water, the cell will shrivel and shrink. Eventually they die, as their metabolism is disrupted i.e. badly wilted plants never recover fully.

Conversely, cells in a hypotonic (or weaker) solution will absorb water by osmosis until equilibrium is reached, since the cell has the lower water potential, and water ‘flows downhill’.

This flow of water into a cell causes it to swell:

a. Animal cells placed in a hypotonic solution will swell and often burst because of osmosis. N.B. The bursting of cells is called cytolysis.

b. Plant, fungal and bacterial cells do not burst because of their cell wall. The pressure that the cell exerts against the cell wall is its pressure potential Ψp. These cells are normally in this state, i.e. turgid.

In an isotonic solution, the concentration of solutes on both sides of the membrane is the same and so the net movement of water is zero. This is the normal position inside an animal’s body.

HOW CELLS DEAL WITH OSMOSIS

Cells that are exposed to an isotonic environment have no difficulty keeping the movement of water across the cell membrane in balance. This includes all land and most marine animals.

However, cells functioning in a hypotonic environment, such as Protoctista living in fresh water have a problem, as water will constantly enter them, down the water potential gradient, from their surroundings.

Since they cannot lower their water potential to near-zero, such organisms must rid themselves of the excess water.

Some (e.g. Paramecium sp. – see above) have contractile vacuoles, which actively pump water out of the cell.

This pumping action requires energy – so is a form of active transport. Up to 30% of the cell’s energy may be used in this way.

Plant root cells also live in hypotonic environment, so water (only!) normally moves by osmosis into the root hair cells, until they are turgid. Water then moves from these cells into the xylem down the water potential gradient.

In a hypertonic environment, water leaves the cells by osmosis, the cell membrane shrinks away from the cell wall, and turgor is lost. This condition is called plasmolysis, and is the reason plants wilt.

FACILITATED DIFFUSION

Passive transport across a membrane requires no energy input from the cell and always goes down the concentration gradient. Simple diffusion and osmosis are examples of passive transport.

However, most molecules cannot cross the membrane by simple diffusion; to do so, the molecule must either be very small (H2O, CO2) or be soluble in both water and lipid (ethanol).

Some molecules are carried across the membrane by carrier proteins which are embedded in the cell membrane.

Carrier proteins often change shape when molecules attach to them, and this change in shape enables the molecule to cross the membrane.

Because the carrier protein has to fit around the molecule, it is specific to one molecule, or related class of molecules.

This use of carrier proteins to cross the membrane is known as facilitated diffusion, and can be used by those molecules to cross the membrane in either direction – into or out of the cell.

Like simple diffusion, facilitated diffusion always goes down the concentration gradient, and therefore continues until equilibrium is reached, for that molecule.

A good example of facilitated diffusion is the transport of glucose into the cell. Once inside the cell, the glucose is immediately turned into glucose phosphate, for which no carrier protein exists. Glucose will thus continue to enter the cell, since equilibrium can never be reached!

Facilitated diffusion is therefore another form of passive transport, since it requires no energy input from the cell.

Some molecules, mainly ions (e.g. Na+, K+) cross the membrane through tunnels made of protein called ion channels.

Some ion channels are always open, but others (e.g. in neurones) have ‘gates’ that open to allow ions to pass or close to stop their passage.

Gates open and close in response to conditions in the external environment, or in the cell. It is the opening and closing of the sodium and potassium gates that allows a nerve impulse to be formed and passed along a neurone.

ACTIVE TRANSPORT (using ATP energy)

Cells often move molecules across the membrane against the concentration gradient, i.e. from an area of low concentration to an area of high concentration.

This requires energy (uses ATP), and is known as active transport.

Active transport involves the use of carrier proteins, similar to those of facilitated diffusion, but these carrier proteins act as pumps, using the energy from splitting ATP to pump specific molecules against the concentration gradient.

These carrier proteins are known as membrane pumps, and are particularly important in maintaining the Na+ /K+ ion balance between Eukaryotic cells and their external environment.

The sodium/potassium (Na+ /K+) pump maintains a high concentration of Na+ ions outside the cell, and a high concentration of K+ ions inside the cell. This is particularly important in muscle contractions, nerve impulses and the absorption of nutrients from the gut.

The Na+/K+ ion pump moves Na+ ions out of the cell, and K+ ions into the cell, against their concentration gradient, using ATP to supply the energy needed.

In plants, active transport enables roots to absorb mineral ions from the soil, which are therefore more concentrated inside plant cells than in the soil.

This requires ATP energy from aerobic respiration, and therefore roots need oxygen to allow mineral uptake and a waterlogged (thus anaerobic) soil will kill most roots.

Osmosis using osmometer

2011-02-27T23:19:00.000+08:00

Fluid Mosaic Model

2011-02-23T22:56:00.000+08:00

A Frog's Fate

2011-02-15T23:32:00.000+08:00

What is AIDS?

2011-02-08T23:05:00.001+08:00

What does AIDS mean?

AIDS stands for Acquired Immune Deficiency Syndrome:

Acquired means you can get infected with it;

Immune Deficiency means a weakness in the body's system that fights diseases.

Syndrome means a group of health problems that make up a disease.

AIDS is caused by a virus called HIV, the Human Immunodeficiency Virus. If you get infected with HIV, your body will try to fight the infection. It will make "antibodies," special molecules to fight HIV.

A blood test for HIV looks for these antibodies. If you have them in your blood, it means that you have HIV infection. People who have the HIV antibodies are called "HIV-Positive.

Being HIV-positive, or having HIV disease, is not the same as having AIDS. Many people are HIV-positive but don't get sick for many years. As HIV disease continues, it slowly wears down the immune system. Viruses, parasites, fungi and bacteria that usually don't cause any problems can make you very sick if your immune system is damaged. These are called "opportunistic infections."

How do you get AIDS?

You don't actually "get" AIDS. You might get infected with HIV, and later you might develop AIDS. You can get infected with HIV from anyone who's infected, even if they don't look sick and even if they haven't tested HIV-positive yet. The blood, vaginal fluid, semen, and breast milk of people infected with HIV has enough of the virus in it to infect other people. Most people get the HIV virus by:

* having sex with an infected person

* sharing a needle (shooting drugs) with someone who's infected

* being born when their mother is infected, or drinking the breast milk of an infected woman

Getting a transfusion of infected blood used to be a way people got AIDS, but now the blood supply is screened very carefully and the risk is extremely low.

There are no documented cases of HIV being transmitted by tears or saliva, but it is possible to be infected with HIV through oral sex or in rare cases through deep kissing, especially if you have open sores in your mouth or bleeding gums.

What happens if I'm HIV positive?

You might not know if you get infected by HIV. Some people get fever, headache, sore muscles and joints, stomach ache, swollen lymph glands, or a skin rash for one or two weeks. Most people think it's the flu. Some people have no symptoms.

The virus will multiply in your body for a few weeks or even months before your immune system responds. During this time, you won't test positive for HIV, but you can infect other people.

When your immune system responds, it starts to make antibodies. When this happens, you will test positive for HIV.

After the first flu-like symptoms, some people with HIV stay healthy for ten years or longer. But during this time, HIV is damaging your immune system.

One way to measure the damage to your immune system is to count your CD4 cells you have. These cells, also called "T-helper" cells, are an important part of the immune system. Healthy people have between 500 and 1,500 CD4 cells in a milliliter of blood.

Without treatment, your CD4 cell count will most likely go down. You might start having signs of HIV disease like fevers, night sweats, diarrhea, or swollen lymph nodes. If you have HIV disease, these problems will last more than a few days, and probably continue for several weeks.

How do I know if I have AIDS?

HIV disease becomes AIDS when your immune system is seriously damaged. If you have less than 200 CD4 cells or if your CD4 percentage is less than 14%, you have AIDS. See If you get an opportunistic infection, you have AIDS. There is an "official" list of these opportunistic infections put out by the Centers for Disease Control (CDC). The most common ones are:

* PCP (Pneumocystis pneumonia), a lung infection;

* KS (Karposi's sarcoma), a skin cancer;

* CMV (Cytomegalovirus), an infection that usually affects the eyes

* Candida, a fungal infection that can cause thrush (a white film in your mouth) or infections in your throat or vagina

AIDS-related diseases also includes serious weight loss, brain tumours, and other health problems. Without treatment, these opportunistic infections can kill you.

AIDS is different in every infected person. Some people die a few months after getting infected, while others live fairly normal lives for many years, even after they "officially" have AIDS. A few HIV-positive people stay healthy for many years even without taking antiretroviral medications (ARVs).

Is there a cure for AIDS?

There is no cure for AIDS. There are drugs that can slow down the HIV virus, and slow down the damage to your immune system. There is no way to "clear" the HIV out of your body.

Other drugs can prevent or treat opportunistic infections (OIs). In most cases, these drugs work very well. The newer, stronger ARVs have also helped reduce the rates of most OIs. A few OIs, however, are still very difficult to treat.

Movement of water from soil to leaves

2011-02-08T22:56:00.001+08:00

i) from soil to roots
- water diffuse into the cell of root hairs by osmosis
- concentration of water in the cell is lower than outside the cell/soil
- cell becomes hypotonic to the adjacent cells by osmosis
- osmosis goes on until water molecules reach the xylem vessels

ii) roots up the stem
- transpirational pull draws water upwards
- cohesive forces between water molecules
- adhesive forces between water molecules and the wall of xylem vessels
- generates capillary action

iii) from the leaves to the atmosphere
- water evaporates from the surface of the mesophyll cells into the air spaces/surrounding
- water which is lost, is replaced by water in the xylem by osmosis
- water vapour diffuses out/evaporates into the atmosphere through the stomata

Analogy of the cell

2011-02-01T00:16:00.000+08:00

Nucleus (a cell's information center) would be the school's general office where all information about the student , school etc are.

Nucleolus would be the principal who is "located" inside the nucleus controlling the running of the school.

Like how important the nucleus & the nucleolus is to the cell, the principal & the school's general office are very important to the school too & they both control the running of the cell & school.

Plasma membrane (regulates the movement of water, nutrients and wastes into and out of the cell.) would be like the school's security guard.

Like the plasma membrane, the school's security guard prevents students from leaving the school during school hours & prevents strangers from entering the school.

Mitochondria (the power generators) would be the school's canteen where all types of food are & where all students and teachers get their food .

Like the mitochondria, the school canteen provides food for the students & teachers giving them energy to last for the day.

Rough Endoplasmic Reticulum (moves materials around the cell) would be like the teachers in the school.

Like the rough endoplasmic reticulum, the teachers teach the students thus providing them with information, circulating their knowledge around the school.

Ribosomes (make proteins) would be like the students in the school.

Like the ribosomes , students would produce good results for the school like how ribosomes make proteins for the cell .

Lysosomes (chemicals used to digest waste) would be like the cleaners we have in the school.

Like the lysosomes , the cleaners in the school help to clear all rubbish and help clean the school in turn making the school a clean environment to study in. Like the importance of the lysosomes, the cleaners are important in a school too.

Golgi apparatus (packing & secreting of energy) would be like the Head of the panel (Ketua Panitia).

Like the golgi apparatus, the Head of the panel,decides in what way should the teachers be teaching the students . Like how the golgi apparatus and the rough endoplasmic reticulum work closely together, the Head of each panels work closely with the teachers too.

Tata.....my cell analogy of school

Dissecting the Frog

2011-01-24T22:48:00.001+08:00

Background

As members of the class Amphibia, frogs may live some of their adult lives on land, but they must return to water to reproduce. Eggs are laid and fertilised in water. On the outside of the frog’s head are two external nares, or nostrils; two tympani, or eardrums; and two eyes, each of which has three lids. The third lid, called the nictitating membrane, is transparent. Inside the mouth are two internal nares, or openings into the nostrils; two vomerine teeth in the middle of the roof of the mouth; and two maxillary teeth at the sides of the mouth. Also inside the mouth behind the tongue is the pharynx, or throat.

In the pharynx, there are several openings: one into the oesophagus, the tube into which food is swallowed; one into the glottis, through which air enters the larynx, or voice box; and two into the Eustachian tubes, which connect the pharynx to the ear. The digestive system consists of the organs of the digestive tract, or food tube, and the digestive glands. From the oesophagus, swallowed food moves into the stomach and then into the small intestine. Bile is a digestive juice made by the liver and stored in the gallbladder. Bile flows into a tube called the common bile duct, into which pancreatic juice, a digestive juice from the pancreas, also flows. The contents of the common bile duct flow into the small intestine, where most of the digestion and absorption of food into the bloodstream takes place.

Indigestible materials pass through the large intestine and then into the cloaca, the common exit chamber of the digestive, excretory, and reproductive systems. The respiratory system consists of the nostrils and the larynx, which opens into two lungs, hollow sacs with thin walls. The walls of the lungs are filled with capillaries, which are microscopic blood vessels through which materials pass into and out of the blood. The circulatory system consists of the heart, blood vessels, and blood. The heart has two receiving chambers, or atria, and one sending chamber, or ventricle. Blood is carried to the heart in vessels called veins. Veins from different parts of the body enter the right and left atria. Blood from both atria goes into the ventricle and then is pumped into the arteries, which are blood vessels that carry blood away from the heart.

The urinary system consists of the frog’s kidneys, ureters, bladder, and cloaca. The kidneys are organs that excrete urine. Connected to each kidney is a ureter, a tube through which urine passes into the urinary bladder, a sac that stores urine until it passes out of the body through the cloaca. The organs of the male reproductive system are the testes, sperm ducts, and cloaca. Those of the female system are the ovaries, oviducts, uteri, and cloaca. The testes produce sperm, or male sex cells, which move through sperm ducts, tubes that carry sperm into the cloaca, from which the sperm move outside the body. The ovaries produce eggs, or female sex cells, which move through oviducts into the uteri, then through the cloaca outside the body.

The central nervous system of the frog consists of the brain, which is enclosed in the skull, and the spinal cord, which is enclosed in the backbone. Nerves branch out from the spinal cord. The frog’s skeletal and muscular systems consist of its framework of bones and joints, to which nearly all the voluntary muscles of the body are attached. Voluntary muscles, which are those over which the frog has control, occur in pairs of flexors and extensors. When a flexor of a leg or other body part contracts, that part is bent. When the extensor of that body part contracts, the part straightens.

Objectives:

• Describe the appearance of various organs found in the frog.

• Name the organs that make up various systems of the frog.

Purpose:

You will dissect a frog in order to observe the external and internal structures of frog anatomy.

Materials:

• safety goggles, gloves, and a lab apron

• forceps

• preserved frog

• dissecting pins (6–10)

• dissecting tray and paper towels

• plastic storage bag and twist tie

• scissors

• marking pen

• dissecting needle

Procedure:

1. Put on safety goggles, gloves, and a lab apron.

2. Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its "thumbs," which is one external difference between the sexes, as shown in the diagram below. Male frogs are also usually smaller than female frogs. Observe several frogs to see the difference between males and females.

3. Use the diagram below to locate and identify the external features of the head. Find the mouth, external nares, tympani, eyes, and nictitating membranes.

4. Turn the frog on its back and pin down the legs. Cut the hinges of the mouth and open it wide. Use the diagram below to locate and identify the structures inside the mouth. Use a probe to help find each part: the vomerine teeth, the maxillary teeth, the internal nares, the tongue, the openings to the Eustachian tubes, the oesophagus, the pharynx, and the slit-like glottis.

5. Look for the opening to the frog’s cloaca, located between the hind legs. Use forceps to lift the skin and use scissors to cut along the center of the body from the cloaca to the lip. Turn back the skin, cut toward the side at each leg, and pin the skin flat. The diagram above shows how to make these cuts.

6. Lift and cut through the muscles and breast bone to open up the body cavity. If your frog is a female, the abdominal cavity may be filled with dark-colored eggs. If so, remove the eggs on one side so you can see the organs underlying them.

7. Use the diagram below to locate and identify the organs of the digestive system: esophagus, stomach, small intestine, large intestine, cloaca, liver, gallbladder, and pancreas.

8. Again refer to the diagram below to identify the parts of the circulatory and respiratory systems that are in the chest cavity. Find the left atrium, right atrium, and ventricle of the heart. Find an artery attached to the heart and another artery near the backbone. Find a vein near one of the shoulders. Find the two lungs.

9. Use a probe and scissors to lift and remove the intestines and liver. Use the diagram on the next page to identify the parts of the urinary and reproductive systems. Remove the peritoneal membrane, which is connective tissue that lies on top of the red kidneys. Observe the yellow fat bodies that are attached to the kidneys. Find the ureters; the urinary bladder; the testes and sperm ducts in the male; and the ovaries, oviducts, and uteri in the female.

10. Remove the kidneys and look for threadlike spinal nerves that extend from the spinal cord. Dissect a thigh, and trace one nerve into a leg muscle. Note the size and texture of the leg muscles.

11. Dispose of your materials according to the directions from your teacher.

12. Clean up your work area and wash your hands before leaving the lab.

Plant Tissues

2011-01-22T15:58:00.001+08:00

A mature vascular plant, e.g., a tobacco plant, contains several differentiated cell types. These are grouped together in tissues. Some tissues contain only one type of cell. Some consist of several.

Meristematic

The main function of meristematic tissue is mitosis. The cells are small, thin-walled, with no central vacuole and no specialised features.

Meristematic tissue is located in
-the apical meristems at the growing points of roots and stems.
-the secondary meristems (lateral buds) at the nodes of stems (where branching occurs), and in some plants,
-a ring of meristematic tissue, called the cambium, that is found within the mature stem.
The cells produced in the meristems soon become differentiated into one or another of several types.

Protective

Protective tissue covers the surface of leaves and the living cells of roots and stems. Its cells are flattened with their top and bottom surfaces parallel. The upper and lower epidermis of the leaf are examples of protective tissue.

Parenchyma

The cells of parenchyma are large, thin-walled, and usually have a large central vacuole. They are often partially separated from each other. They are usually stuffed with plastids.

In areas not exposed to light, colorless plastids predominate and food storage is the main function. The cells of the white potato are parenchyma cells.

Where light is present, e.g., in leaves, chloroplasts predominate and photosynthesis is the main function.

Sclerenchyma

The walls of these cells are very thick and built up in a uniform layer around the entire margin of the cell. Often, the protoplasts die after the cell wall is fully formed. Sclerenchyma cells are usually found associated with other cells types and give them mechanical support.

Sclerenchyma is found in stems and also in leaf veins. Sclerenchyma also makes up the hard outer covering of seeds and nuts.

Collenchyma

Collenchyma cells have thick walls that are especially thick at their corners. These cells provide mechanical support for the plant. They are most often found in areas that are growing rapidly and need to be strengthened. The petiole ("stalk") of leaves is usually reinforced with collenchyma.

Vascular Tissues
Xylem

Xylem conducts water and dissolved minerals from the roots to all the other parts of the plant.

In angiosperms, most of the water travels in the xylem vessels. These are thick-walled tubes that can extend vertically through several feet of xylem tissue. Their diameter may be as large as 0.7 mm. Their walls are thickened with secondary deposits of cellulose and are usually further strengthened by impregnation with lignin. The secondary walls of the xylem vessels are deposited in spirals and rings and are usually perforated by pits.

Xylem vessels arise from individual cylindrical cells oriented end to end. At maturity the end walls of these cells dissolve away and the cytoplasmic contents die. The result is the xylem vessel, a continuous non-living duct. The vessels carry water and some dissolved solutes, such as inorganic ions, up the plant.

Xylem also contains tracheids. These are individual cells tapered at each end so the tapered end of one cell overlaps that of the adjacent cell. Like xylem vessels, they have thick, lignified walls and, at maturity, no cytoplasm. Their walls are perforated so that water can flow from one tracheid to the next. The xylem of ferns and conifers contains only tracheids.

In woody plants, the older xylem ceases to participate in water transport and simply serves to give strength to the trunk. Wood is xylem. When counting the annual rings of a tree, one is counting rings of xylem.

Phloem
The main components of phloem are
-sieve elements and
-companion cells.

Sieve elements are so-named because their end walls are perforated. This allows cytoplasmic connections between vertically-stacked cells. The result is a sieve tube that conducts the products of photosynthesis - sugars and amino acids - from the place where they are manufactured (a "source"), e.g., leaves, to the places ("sinks") where they are consumed or stored; such as

-roots
-growing tips of stems and leaves
-flowers
-fruits, tubers, corms, etc.

Sieve elements have no nucleus and only a sparse collection of other organelles. They depend on the adjacent companion cells for many functions.

Companion cells move sugars and amino acids into and out of the sieve elements. In "source" tissue, such as a leaf, the companion cells use transmembrane proteins to take up - by active transport - sugars and amino acids from the cells manufacturing them. Water follows by osmosis. These materials then move into adjacent sieve elements by diffusion through plasmodesmata. The pressure created by osmosis drives the flow of materials through the sieve tubes.

In "sink" tissue, the sugars and amino acids leave the sieve tubes by diffusion through plasmodesmata connecting the sieve elements to the cells of their destination. Again, water follows by osmosis where it may

-leave the plant by transpiration or
-increase the volume of the cells or
-move into the xylem for recycling through the plant.

Animal and Plant Cells

2011-01-22T15:46:00.000+08:00

Fluid Exchange

2011-01-16T23:46:00.001+08:00

Capillaries are composed of a single layer of squamos epithelium surrounded by a thin basement membrane. Most capillaries (except those servicing the nervous system) have pores (spaces) between the individual cells that make up the capillary wall. Plasma fluid and small nutrient molecules leave the capillary and enter the interstitial fluid through these pores, in a process called bulk flow. Bulk flow facilitates the efficient transfer of nutrient out of the blood and into the tissues. However, blood cells and plasma proteins, which are too large to fit through the pores, do not filter out of the capillaries by bulk flow.

Together, blood plasma and interstitial fluid make up the extracellular fluid (ECF). Plasma constitutes 20%, while interstitial fluid constitutes 80% of the ECF. The distribution of extracellular fluid between these two compartments is determined by the balance between two opposing forces: hydrostatic pressure and osmotic pressure.

The beating of the heart generates hydrostatic pressure, which, in turn, causes bulk flow of fluid from plasma to interstitial fluid through walls of the capillaries. In other words, the pressure in the system forces plasma to filter out into the interstitial compartment. The composition of the interstitial fluid and the plasma is essentially the same except that plasma also contains plasma proteins not found in the interstitial fluid. Because of the presence of plasma proteins, the plasma has a higher solute concentration than does the interstitial fluid. Consequently, osmotic pressure causes interstitial fluid to be absorbed into the plasma compartment. In other words, the plasma proteins drive the reabsorption of water back into the capillaries via osmosis.

The magnitudes of filtration and absorption are not equal. The net filtration of fluid out of the capillaries into the interstitial compartment is greater than the net absorption of fluid back into the capillaries. The excess filtered fluid is returned to the blood stream via the lymphatic system. In addition to its roles in digestion and immunity, the lymphatic system functions to return filtered plasma back to the circulatory system. The smallest vessels of the lymphatic system are the lymphatic capillaries (shown in yellow). These porous, blind-ended ducts form a large network of vessels that infiltrate the capillary beds of most organs. Excess interstitial fluid enters the lymphatic capillaries to become lymph fluid.

Lymphatic capillaries converge to form lymph vessels that ultimately return lymph fluid back to the circulatory system via the subclavian vein. The presence of one-way valves in the lymph vessels ensures unidirectional flow of lymph fluid toward the subclavian vein.

If excess fluid cannot be returned to the blood stream then interstitial fluid builds up, leading to swelling of the tissues with fluid, this is called oedema.

Causes of Oedema

1. Reduced concentration of plasma proteins. When the concentration of plasma proteins drops, the osmotic potential of plasma drops, thus less interstitial fluid is absorbed into the capillaries. The rate of filtration, however, remain unchanged. Therefore, the ratio of filtration to absorption increases, leading to a build up of interstitial fluid. Any condition that would lead to a reduction in plasma proteins could potentially cause edema. Examples of conditions that reduce plasma proteins include:

a) Kidney disease can result in the loss of plasma proteins in the urine.
b) Liver disease can decrease the synthesis of plasma proteins.
c) A protein-deficient diet will decrease plasma proteins.
d) Severe burns result in a loss of plasma proteins (albumin) at the burn site

2. Increased capillary permeability. During an inflammatory response, tissue damage leads to the release of histamine from immune cells. Histamine causes an increase in the size of capillary pores. As capillaries become more permeable, the rate of filtration increases.

3. Increase in venous pressure. If venous pressure is increased then blood dams up in the upstream capillary bed, resulting in excess filtration. Examples of this condition include:

a) Left heart failure. The left half of the heart drains blood from the lungs. When the left ventricle fails to adequately pump blood, venous pressure in the lungs increases. This increases in hydrostatic pressure causes an increase in the rate of filtration of fluid out of the capillaries and into the interstitial compartment. As a result, the lungs fill with fluid, a condition called, pulmonary oedema.

b) Standing still. If one stands still for long period of time, then blood will pool in the veins of the legs. This will increase venous pressure and lead to weeping of fluid into the tissues. You can actually feel your feet swell if you stand motionless for a long time.

4. Blocked Lymphatic Vessels. If lymph vessels become blocked, then lymph fluid will not be drained from the affected area and the area will swell. Any condition that causes blockage or removal of lymph vessels can lead to oedema. Examples of this condition include:

a) Filaria round worms are transmitted to humans by some species of mosquitoes. The worms migrate to the lymph vessels and block them. This causes dramatic swelling of the affected area, a condition called elephantiasis.

b) Treatment for breast cancer may include removal of lymph vessels from breast and arms. This is done to limit the metastasis (spread) of cancerous cells to other parts of the body through the lymph. Removal of lymph vessels results in swelling of the affected area.

Heart Attack

2011-01-16T23:35:00.001+08:00

Heart With Muscle Damage and a Blocked Artery

A heart attack occurs when blood flow to a section of heart muscle becomes blocked. If the flow of blood isn’t restored quickly, the section of heart muscle becomes damaged from lack of oxygen and begins to die.

Fortunately, today there are excellent treatments for heart attack that can save lives and prevent disabilities. Treatment is most effective when started within 1 hour of the beginning of symptoms.

Heart attacks occur most often as a result of a condition called coronary artery disease (CAD). In CAD, a fatty material called plaque builds up over many years on the inside walls of the coronary arteries (the arteries that supply blood and oxygen to your heart). Eventually, an area of plaque can rupture, causing a blood clot to form on the surface of the plaque. If the clot becomes large enough, it can mostly or completely block the flow of oxygen-rich blood to the part of the heart muscle fed by the artery.

Figure A is an overview of a heart and coronary artery showing damage (dead heart muscle) caused by a heart attack. Figure B is a cross-section of the coronary artery with plaque buildup and a blood clot.

During a heart attack, if the blockage in the coronary artery isn’t treated quickly, the heart muscle will begin to die and be replaced by scar tissue. This heart damage may not be obvious, or it may cause severe or long-lasting problems.

Severe problems linked to heart attack can include heart failure and life-threatening arrhythmias (irregular heartbeats). Heart failure is a condition in which the heart can’t pump enough blood throughout the body. Ventricular fibrillation is a serious arrhythmia that can cause death if not treated quickly.

Acting fast at the first sign of heart attack symptoms can save your life and limit damage to your heart. Treatment is most effective when started within 1 hour of the beginning of symptoms.

The most common heart attack signs and symptoms are:

Chest discomfort or pain—uncomfortable pressure, squeezing, fullness, or pain in the center of the chest that can be mild or strong. This discomfort or pain lasts more than a few minutes or goes away and comes back.
Upper body discomfort in one or both arms, the back, neck, jaw, or stomach.
Shortness of breath may occur with or before chest discomfort.
Other signs include nausea (feeling sick to your stomach), vomiting, lightheadedness or fainting, or breaking out in a cold sweat.

Susah ka nak score Bio nie??

2011-01-06T21:28:00.002+08:00

1. Slow down !!

The flow of a biology book is not like the flow of a novel. A novel can be read effortlessly, smoothly and rapidly, but biology books cannot. If you are reading a novel and are somewhat distracted, you can still get the idea of what it is about. When you are not concentrating on biology you will get very little out of it, and it will seem more difficult than it really is.

2. Every word counts.

Biology books are usually not repetitive, so there is little chance of picking something up from reading on. Writers of biology texts believe that extra words and repeats get in the way of clarity.

3. It is best to tackle each chapter at least three times.

The first time you should skim the chapter, noting topic sentences, words in bold print, all tables, diagrams and summary charts. This is best read before the class. The second reading should be in more detail, studying each area and not proceeding until each section is understood. Reread each section as many times as necessary until you understand its meaning. Mastery can take minutes or hours or days. The last major reading is for writing down terms and definitions and important concepts (see #5 below).

4. Talk to yourself as you read.

Explain what you have read aloud and make up your own examples to better understand what you have read. Rereading the material aloud, especially in your own words helps clarify the information. Hearing yourself makes a lot of difference.

5. Words and symbols of biology have specific meanings.

Each time you come to a new term or concept, cover up the text and see if you can express the idea aloud in your own words. Write down all the words you do not know. Emphasise words in bold type. Whenever possible write out the definitions in your own words. Strive for understanding the definitions so that you can easily state them in your own words; you are more likely to remember them that way. By saying it out loud and writing it, you are more like to recall it later, when needed.

6. Study all diagrams and charts.

They condense a lot of valuable information. Cover up and see if you can visualise them.

7. Write as you read.

During your first reading write nothing in the text.
Do not highlight ¬ it slows down reading and it is often used as an excuse for not concentrating.
In a later reading, call attention to important words or phrases by underlining them (do not overdo this).
Complete sentences or paragraphs should be bracketed and not underlined.
Write summarising statements to yourself in the margin.
Make notes to yourself right in the text.
Note questions that you need to have clarified.
DO NOT WORRY ABOUT THE RESALE VALUE OF THE TEXT.

8. Record all key points on a separate sheet.

9. If there are study questions at the end of the chapters, be sure you can answer them. They are good practice for the exam.

10. Make flash cards with terminology and concepts.

11. Keep testing yourself on a separate sheet of paper.

12. Without looking back, write out and say aloud the important points.

13. Create tasks for yourself as you read the text.

14. After reading an example and working it out for yourself, try to think of other examples that would fit the idea being discussed.

15. Use more than one book on the topic you are studying whenever possible.

16. Pick books that appeal to you.

If you are very verbal, a book with long explanations is likely to be most helpful. If you are more visual, you might choose a book that has more illustrations.

17. Read the chapter before, and again after, class.
You will get the most out of class if you have read the material before the teacher presents it. Even if you feel that you understood the material in class, read it over again in the text. The more you review it the more likely you are to recall it.

18. If possible, have a friend or family member quiz you on your notes and text information.

Done regularly, this commits more information to long-term memory.

Good luck guys...

Circulation

2011-01-06T21:14:00.000+08:00

In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system. There is no distinction between blood and interstitial fluid, and this general body fluid is more correctly termed haemolymph. One or more hearts pump the haemolymph into an interconnected system of sinuses, which are spaces surrounding the organs. Here, chemical exchange occurs between the haemolymph and body cells. In insects and other arthropods, the heart is an elongated tube located dorsally. When the heart contracts, it pumps haemolymph through vessels out into sinuses. When the heart relaxes, it draws haemolymph into the circulatory system through pores called ostia. Body movements that squeeze the sinuses help circulate the haemolymph.

The mammalian cardiovascular system : Note that the dual circuits operate simultaneously, not in the serial fashion that the numbering in the diagram suggests. The two ventricles pump almost in unison; while some blood is traveling in the pulmonary circuit, the rest of the blood is flowing in the systemic circuit.

Located beneath the breastbone (sternum), the human heart is about the size of a clenched fist and consists mostly of cardiac muscle. The two atria have relatively thin walls and serve as collection chambers for blood returning to the heart, most of which flows into the ventricles as they relax. Contraction of the atria completes filling of the ventricles. The ventricles have thicker walls and contract much more strongly than the atria—especially the left ventricle, which must pump blood to all body organs through the systemic circuit.

The cardiac cycle. For an adult human at rest with a pulse of about 75 beats per minute, one complete cardiac cycle takes about 0.8 second.

1 During a relaxation phase (atria and ventricles in diastole), blood returning from the large veins flows into the atria and ventricles.

2 A brief period of atrial systole then forces all remaining blood out of the atria into the ventricles.

3 During the remainder of the cycle, ventricular systole pumps blood into the large arteries.

Note that seven–eighths of the time—all but 0.1 second of the cardiac cycle—the atria are relaxed and are filling with blood returning via the veins.

A region of the heart called the sinoatrial (SA) node, or pacemaker, sets the rate and timing at which all cardiac muscle cells contract. Composed of specialised muscle tissue, the SA node is located in the wall of the right atrium, near the point where the superior vena cava enters the heart. Because the pacemaker of the human heart (and of other vertebrates) is made up of specialised muscle tissues and located within the heart itself, the vertebrate heart is referred to as a myogenic heart.

The SA node generates electrical impulses much like those produced by nerve cells. Because cardiac muscle cells are electrically coupled (by the intercalated disks between adjacent cells), impulses from the SA node spread rapidly through the walls of the atria, causing both atria to contract in unison.

The impulses also pass to another region of specialised cardiac muscle tissue, a relay point called the atrioventricular (AV) node, located in the wall between the right atrium and right ventricle. Here the impulses are delayed for about 0.1 second before spreading to the walls of the ventricles. The delay ensures that the atria empty completely before the ventricles contract. Specialised muscle fibres called bundle branches/his and Purkinje fibres then conduct the signals to the apex of the heart and throughout the ventricular walls.

The impulses that travel through cardiac muscle during the heart cycle produce electrical currents that are conducted through body fluids to the skin, where the currents can be detected by electrodes and recorded as an electrocardiogram (ECG or EKG).

TSA/V Ratio

2011-01-06T20:58:00.000+08:00

Geometric relationships between surface area and volume. In this diagram, cells are represented as boxes. Using arbitrary units of length, we can calculate the cell’s surface area (in square units), volume (in cubic units), and ratio of surface area to volume. The smaller the cell, the higher the surface–to–volume ratio. A high surface–to–volume ratio facilitates the exchange of materials between a cell and its environment.

Tips on note taking

2011-01-04T22:53:00.001+08:00

Note Taking

There are basically two types of note taking that a student will be faced with:
1. Making notes in class
2. Making notes as a result of private study and reading

There are many ways of writing notes, each with its own advantages and disadvantages, and it is best to try them all to see which method works for you. Certain subjects or topics may lend themselves to one particular method. The most important point is that they are useful later when you wish to re-use them.

Why make notes?
Notes make you concentrate on what you are learning
Notes make you put ideas into your own words and so aid understanding
Notes help you remember things better
Notes are excellent for revision
Taking notes in class - how to improve your technique

Thankfully, fewer and fewer educators dictate notes these days, realising that dictation goes from ears to hand without stopping in the brain in between! However, many adopt a lecture style where students are required to take notes. In such a situation the following may be helpful:

Don't try to write down everything the educator says

Concentrate on picking out the relevant points only

Write notes in point form with separate sub headings

Develop your own shorthand (see examples below)

Leave plenty of space between your notes for later additions

Jot down any references given in class to read later

Number any handouts issued with a corresponding number in the relevant place in your notes

Underline key phrases in red, or with a highlighter pen

It is always advisable to date and number each sheet of A4 as you use it

Before your next lesson expand on your class notes from text books, etc. using the tips given below

Finally, always ask the teacher for a further explanation if there is something you do not understand - you can be sure there is someone else in the class who has difficulties too!

Taking notes from written sources - how to improve your technique

Using the SQ3R technique outlined in the Reading section you will have read and absorbed information. The next stage is to make a written record in note form using the appropriate method for you. Below are 5 possible methods you may wish to try:

Making notes on books or handouts

Advantages

Quick

Key phrases can be underlined

Comments can be added in the margin

Disadvantages

Can only be used if you own the book!

You haven't summarised points in your own words to reinforce understanding

It is very difficult to revise from these notes later; you will probably have to re-read the whole book/article

In summary, quick in the short term only.

Making summary notes or a precis

This involves reading all the information, working on each paragraph in turn, re-writing in your own words. A brief introductory and concluding paragraph is advisable.

Advantages
Detailed notes obtained
Helps to develop your written style

Disadvantages
Time consuming
Continuous prose is difficult to revise from
The salient points do not stand out easily

In summary, a useful exercise but not 'user friendly' in the future.

Sprays
This involves quickly jotting down all your ideas on a subject and linking them up.

Advantages
Very quick
Good practice for essay plans in the examination
Makes you think analytically

Disadvantages
May not be suitable for more complex notes
Could be difficult to revise from later

In summary, very useful in organising thought processes, especially in the exam room but has limitations for general use.

Example: A spray about the effects of a strong £

Practice this technique by making a spray about regional unemployment problems
Visual and pattern notes

This method involves using flow diagrams or 'concept trees' (another name for pattern notes) to record information.

Advantages
Can sum up many pages of written notes
You concentrate on the fundamentals
Very active form of learning
Visual images are a great aid to recall
Add a 'fun' element to note taking

Disadvantages
Could be too absorbing!
May be difficult to express more complex ideas clearly

In summary, a valuable supplement to 'linear notes'.

Linear Notes

This method involves reorganising information in a written format using your own shorthand and personal style.

Advantages
Makes you think analytically
Aids your understanding
Simple to revise from and use later

Disadvantages
Initially quite time consuming
Doesn't aid visual memory like pattern notes

In summary, initially takes some thought and time but probably most useful method for expressing complex ideas clearly.

Some tips!

Use titles, subtitles and bullet points

Avoid lengthy prose

Underline key points in red or with a highlighter

Produce a summary list/table at the end of a section

Don't be afraid to produce tables e.g. Advantages & Disadvantages of...

Include topical examples and case study references in your notes as you go along but remember you would only have time to write a paragraph in an examination answer so this is how long it should be!

Write memory jogs to yourself in the margin e.g. 'Good diagram p 146 in Book X'

Develop your own shorthand

Wanna be a good student?

2011-01-02T00:07:00.004+08:00

Have you ever wondered why some students get all the A's? It's not luck. Good students have consistent, productive behaviours that work. If you would like to know what they are, read on.

Come to class on time. Students who walk in late are not only disrupting the teacher, they may be missing valuable information or the best seat in the classroom. Arriving a few minutes early is a lot different than arriving a few minutes late.

Sit in the front row. Not only will you be able to see and hear the teacher better, you will also be far away from mooching students who tend to sit in the back.

Be sure that you know the syllabus and then study it carefully. If your teacher goes through it during class, be sure to write down any additional information he or she may provide. Put your syllabus in a safe place and DO NOT LOSE IT.

Learn your teacher's name and what he or she likes to be called. "Mr." "Ms." "Puan" "Cikgu" may be appropriate. Unless your teacher requests otherwise, use his or her last name to convey the proper respect.

Come to class ready to learn. Be sure that you have gone to the bathroom, got something to eat, and have all your necessary books, pens, and paper. You should not be getting up and leaving in the middle of class on a regular basis. Save those types of behaviours for an emergency.

Be prepared by taking good notes. What if you never taken notes before and you're not sure how? The only answer is to practice. Some guidance classes will teach you how to write notes if you need help, but mostly, learning how to listen for and write down important information comes from the experience of actually doing it. You should be taking notes every time your teacher teaches and then storing them in a safe place. Refer to your notes just after leaving class; this way your mind will still be fresh.

Get the phone numbers of at least two other class members. That way, if you miss a class, you can call to find out what you missed. Remember, it is your responsibility to know the information that your teacher presents and that is covered in the book. Don't expect a teacher to regive a lecture that they already gave in class. If you haven't spoken to anyone in the class, simply approach them and ask, "Would you like to exchange phone numbers? I always like to have someone's number in case I miss anything." Most students are happy to have a buddy they can rely on. Its a win-win situation.

Start working on an assignment as soon as possible. Time goes by faster than you expect it to, and we can't always foresee incidents that will get in the way of our homework. Also, if you plan to get an A on your assignment, you will probably need to spend hours working on it. A lot of people aren't willing to do the work required to get an A. Others are. If you have any questions about how to do the assignment or when to turn it in, consult your syllabus and then your teacher.

Turn in all assignments/homework! (extra credit is only optional if you are earning a good grade.) This would seem like a no-brainer, but many students fail to do this. Also, be very familiar with assignment make-up policies. If you have a special situation, talk to your teacher.

If you are assigned to do group work, whether its discussion or turning in a presentation, be a good group member. That means that in a group, you are working just as hard as if you were on your own. Bring your ideas and your feedback to the table. Be serious about the assignment. Taking the attitude of, "I'm so bad at this stuff; you guys can handle it. Your ideas are way better than mine," is not being modest; it's being lazy. In the case of discussion, you are depriving your classmates of the feedback they should have received from you. And in the case of an assignment, you are making your group members do all the work! Don't cop out. In contrast, dominating a group and not allowing everyone to contribute ideas is just as bad. Even if you don't like someone else's ideas, you may need to compromise and go along with it, because group work is supposed to be a group effort.

Learn from your mistakes. That means if your teacher writes, "Use better grammar" than you should study grammar. If your teacher says, "Excellent! But I feel your conclusion is a little weak" than study how to write a conclusion. If you completely bomb a test, that should be a wake-up call to you. If you procrastinate so long that you are not ready with your project, and it turns into a humiliating experience, you need to ask yourself, "What went wrong? Why did I fail, and how could I do it better next time?" Go to your teacher and ask for feedback if you need more clarification.

Have a good attitude. People who show up to a class and complain all the time, writing sms behind the teacher's back, are really only displaying their immaturity. Leave your personal problems at home, show up with a smile, and try to imagine why you might need to know this information, if it doesn't seem obvious.

Tips

When studying, think about your personal learning style and what helps you to remember things. Is it writing notes? Drawing a picture? Teaching it to someone else?
Remember, you are not given a grade, you earn it! Instead of arguing with your teacher about why you should have got an A, ask how you could have done better.

Adios...

What is Biology?

2010-12-31T22:41:00.000+08:00

Happy New Year 2011

2010-12-31T20:11:00.002+08:00

Bygones are bygones! New Year has finally arrived. Time to express gratitude, clear off all the blemishes and complains, motivate the week, congratulate the winners and play pranks on friends. A new start ought to be marked with love and care.

I wish you Health...

So you may enjoy each day in comfort.

I wish you the Love of friends and family...

And Peace within your heart.

I wish you the Beauty of nature...

That you may enjoy the work of God.

I wish you Wisdom to choose priorities...

For those things that really matter in life.

I wish you Generosity so you may share...

All good things that come to you.

I wish you Happiness and Joy...

And Blessings for the New Year.

I wish you the best of everything...

That you so well deserve.

HAPPY NEW YEAR!

New Year's Resolution Tips

2010-12-28T00:22:00.001+08:00

Chances are, at some time in your life, you've made a New Year's Resolution -- and then broken it. This year, stop the cycle of resolving to make change, but then not following through. If your resolution is to take better care of yourself and get your inflammatory bowel disease (IBD) under control, you'll have a much better year if your resolution sticks. Here are some tips to help get you started.

Be realistic

The surest way to fall short of your goal is to make your goal unattainable. For instance, resolving to never eat your favourite food again because it bothers your IBD could be a bad choice. Strive for a goal that is attainable, such as avoiding it more often than you do now.

Plan ahead

Don't make your resolution on New Year's Eve. If you wait until the last minute, it will be based on your mindset that particular day. Instead, it should be planned well before December 31 arrives.

Outline your plan

Decide how you will deal with the temptation to skip that exercise class or have one more cigarette. This could include calling on a friend for help, practicing positive thinking and self-talk, or reminding yourself how your bad habit affects your IBD.

Make a "pro" and "con" list

It may help to see a list of items on paper to keep your motivation strong. Develop this list over time, and ask others to contribute to it. Keep your list with you and refer to it when you need help keeping your resolve.

Talk about it

Don't keep your resolution a secret. Tell friends and family members who will be there to support your resolve to change yourself for the better or improve your health. The best case scenario is to find yourself a buddy who shares your New Year's resolution and motivate each other.

Reward yourself

This doesn't mean that you can eat an entire box of chocolates if your resolution is to diet. Instead, celebrate your success by treating yourself to something that you enjoy that does not contradict your resolution. If you've been sticking to your promise to eat better, for example, perhaps your reward could be going to a movie with a friend.

Track your progress

Keep track of each small success you make toward reaching your larger goal. Short-term goals are easier to keep, and small accomplishments will help keep you motivated. Instead of focusing on losing 30 pounds, say, focus on losing that first 5. Keeping a food diary or a symptom journal may help you stay on track.

Don't beat yourself up

Obsessing over the occasional slip won't help you achieve your goal. Do the best you can each day, and take each day one at a time.

Stick to it

Experts say it takes about 21 days for a new activity, such as exercising, to become a habit, and 6 months for it to become part of your personality. Your new healthful habits will become second-nature in no time.

Keep trying

If your resolution has totally run out of steam by mid-February, don't despair. Start over again! There's no reason you can't make a "New Year's resolution" any time of year.

Fast Facts About New Year's Resolutions

63% of people say they are keeping their resolutions after two months

67% of people make three or more resolutions

Top four resolutions:

Increase exercise

Be more conscientious about work or school

Develop better eating habits

Stop smoking, drinking, or using drugs (including caffeine)

People make more resolutions to start a new habit than to break an old one.

Adios.....

Tips for Time Management

2010-12-26T23:54:00.000+08:00

Perhaps you have a heavy workload and want to find ways to become more effective so you can get more done in less time.

Maybe you feel overwhelmed or “stressed out” and want to find ways to do less and enjoy more. Or maybe you simply want to feel more focused and in control of your time, instead of feeling like you rush madly from one activity to the next until you fall into bed exhausted every night.

Benjamin Franklin said, “Do you love life? Then do not squander time, for that's the stuff that life is made of.”

Time management is a set of principles, practices, skills, tools, and systems working together to help you get more value out of your time with the aim of improving the quality of your life.

The important point is that time management is not necessarily about getting lots of stuff done, because much more important than that is making sure that you are working on the right things, the things that truly need to be done.

Smart time managers know that there is much more to do than anyone could possibly accomplish. So instead of trying to do it all, smart time managers are very picky about how they spend their time.

They choose to focus and spend their time doing a few vital projects that will really make a difference, rather than spending all their time doing many trivial things that don't really matter all that much.

If you become a good time manager, you’ll not only get a lot more done in less time, but you’ll feel more relaxed, focused and in control of your life.

You’ll be able to use your time in a much more balanced and effective way, and you’ll be able to make time for the people and activities that you love. When you get to the end of a busy day, you’ll feel a strong sense of accomplishment from everything that you actually got done.

Improving your time management skills can even help you get better results by doing less work, because you're focusing on the things that really matter rather than all the low-priority busywork that just keeps you busy.

If you don’t learn how to manage your time well, you’ll be far less productive than you could be and you’ll get a lot less done. You’ll also feel much more stressed and overwhelmed, and you’ll struggle to find time to spend with the people you care about and to do the things you enjoy.

In the end, time management comes down to choices. Good choices lead to better results, while poor choices lead to wasted time and energy.

The good news is that time management skills can be learned and mastered by anyone. All it takes is practice and dedication.

Like any other skill, you can learn time management the easy way or you can learn it the hard way.

The hard way usually involves years of trial and error and lots of false starts trying to figure out what works and what doesn't.

If you'd like to save yourself some time, money and effort, I recommend you try the easy way: learn from someone who has already done it.

Makes sense, right?

15 Time Management Tips

In the meantime, here are 15 practical time management tips to help you get started...

1. Write things down

A common time management mistake is to try to use your memory to keep track of too many details leading to information overload. Using a to-do list to write things down is a great way to take control of your projects and tasks and keep yourself organised.

2. Prioritise your list

Prioritising your to-do list helps you focus and spend more of your time on the things that really matter to you. Rate your tasks into categories using the ABCD prioritisation system described in the time management course.

3. Plan your week

Spend some time at the beginning of each week to plan your schedule. Taking the extra time to do this will help increase your productivity and balance your important long-term projects with your more urgent tasks. All you need is fifteen to thirty minutes each week for your planning session.

4. Carry a notebook

You never know when you are going to have a great idea or brilliant insight. Carry a small notebook with you wherever you go so you can capture your thoughts. If you wait too long to write them down you could forget. Another option is to use a digital recorder.

5. Learn to say no

Many people become overloaded with too much work because they overcommit; they say yes when they really should be saying no. Learn to say no to low priority requests and you will free up time to spend on things that are more important.

6. Think before acting

How many times have you said yes to something you later regretted? Before committing to a new task, stop to think about it before you give your answer. This will prevent you from taking on too much work.

7. Continuously improve yourself

Make time in your schedule to learn new things and develop your natural talents and abilities. For example, you could take a class, attend a training program, or read a book. Continuously improving your knowledge and skills increases your marketability, can help boost your career, and is the most reliable path to financial independence.

8. Think about what you are giving up to do your regular activities

It is a good idea to evaluate regularly how you are spending your time. In some cases, the best thing you can do is to stop doing an activity that is no longer serving you so you can spend the time doing something more valuable. Consider what you are giving up in order to maintain your current activities.

9. Use a time management system

Using a time management system can help you keep track of everything that you need to do, organize and prioritise your work, and develop sound plans to complete it. An integrated system is like glue that holds all the best time management practices together.

10. Identify bad habits

Make a list of bad habits that are stealing your time, sabotaging your goals, and blocking your success. After you do, work on them one at a time and systematically eliminate them from your life. Remember that the easiest way to eliminate a bad habit, it to replace it with a better habit.

11. Don’t do other people’s work

Are you in the habit of doing other people’s work because or a ‘hero’ mentality? Doing this takes up time that you may not have. Instead, focus on your own projects and goals, learn to delegate effectively, and teach others how to do their own work.

12. Keep a goal journal

Schedule time to set and evaluate your goals. Start a journal and write down your progress for each goal. Go through your goal journal each week to make sure you are on the right track.

Keeping a journal on your computer has never been easier!

13. Don’t be a perfectionist

Some tasks don’t require your best effort. Sending a short email to a colleague, for example, shouldn’t take any more than a few minutes. Learn to distinguish between tasks that deserve to be done excellently and tasks that just need to be done.

14. Beware of “filler” tasks

When you have a to-do list filled with important tasks, be careful not to get distracted by “filler” tasks. Things such as organising your bookcase or filing papers can wait until you tackle the items that have the highest priority.

15. Avoid “efficiency traps”

Being efficient doesn’t necessarily mean that you are being productive. Avoid taking on tasks that you can do with efficiency that don’t need to be done at all. Just because you are busy and getting things done doesn’t mean you are actually accomplishing anything significant.

Memorising facts in Biology

2010-12-25T01:11:00.001+08:00

Mnemonics can be used wherever possible. don't give it up totally.
Sometimes writing the first letters of names & amp; reading them in a nonsensical & amp; funny way can help.
Write down the points, after reading the answers; draw pictures like parts of the plant, body parts, nerves etc. to connect to the point.,
Write the number of points you have to learn for an answer & amp; arrange them in a sequence easy for you to remember.
When learning objective type answers you can request a family member to ask the qns. This may look funny but mothers are a wonderful support in this.
Divide your portions & amp; learn thoroughly before going to the next one
Don't accumulate too much of study material.
Prepare a time table & amp; follow it sincerely.
Keep your goal in mind & amp; work towards it.

Nothing is impossible when you work hard.
Like what you are doing at present.
Best of luck.

Understand what you are learning and have confidence.

Good relationship with your teachers

2010-12-23T21:37:00.000+08:00

A good relationship between students and teachers makes the classroom a more inviting place. When you like your teacher, it's easier to pay attention to his explanations and improve your grades. When you consider your teacher a friend, you'll certainly have more respect for him. When your teachers consider you to be a friend and not only a student, they'll feel freer in class and that will probably affect the classroom in a very positive way. Now here are some tips to develop a friendly relationship with your teachers:

Ask questions. If you have any questions about that subject, ask them. Teachers like to teach and asking questions is the first way of interacting with them. Show them that you're interested in their subject. That will make them notice you. But never ask questions that you already know the answer to. If your teachers realise that you are not asking real questions, they might think that you're not actually trying to learn, but only trying to make an impression.

No need for compliments. Don't say things like "You look lovely today, Mrs. Lim" or "Did you lose weight, Mr. Smith?" Your teacher will probably think you're being false and only trying to get some advantage, and that's not what you want. Instead, you could do some innocent jokes (jokes that won't offend your teacher). The moment they start doing some of the same jokes (but towards you), then you'll know that your relationship is becoming friendly.

When you see one of your teachers in the hall, greet him and ask if he's going to that concert or if he's seen that movie. That way you'll show that you consider him a friend, and that's why you talk about common subjects. Some teachers don't like to have a friendly relationship with a student, but most of them want to have those simple talks with their students. And after a while, they will start to talk with you about non-school subjects in the class. That will make more students in your class get involved in those talks, and everyone will start to consider that teacher to be a friend.

The rest is totally up to you; it is very easy to develop a friendly relationship with any of your teachers. If you want to be friends with your teachers, just treat them as friends, but don't forget that no matter how good of friends you are, they will still be your teachers and deserve your respect.

Tata.....

Don't give up

2010-12-22T12:06:00.000+08:00

Careers in Bio

2010-12-18T19:09:00.000+08:00

Pursuing a career in biology can be immensely rewarding and exciting. Studying biology teaches us to ask questions, make observations, evaluate evidence, and solve problems. Biologists learn how living things work, how they interact with one another, and how they evolve. They may study cells under a microscope, insects in a rainforest, viruses that affect human beings, plants in a greenhouse, or lions in the African grasslands. Their work increases our understanding about the natural world in which we live and helps us address issues of personal well being and worldwide concern, such as environmental depletion, threats to human health, and maintaining viable and abundant food supplies.

What do biologists do?

There are several career paths you can follow as a biologist, including these:

Research: Research biologists study the natural world, using the latest scientific tools and techniques in both laboratory settings and the outdoors, to understand how living systems work. Many work in exotic locations around the world, and what they discover increases our understanding of biology and may be put to practical use to find solutions to specific problems.

Health care: Biologists may develop public health campaigns to defeat illnesses such as tuberculosis, AIDS, cancer, and heart disease. Others work to prevent the spread of rare, deadly diseases, such as the now infamous Ebola virus. Veterinarians tend to sick and injured animals, and doctors, dentists, nurses, and other health care professionals maintain the general health and well being of their patients.

Environmental management and conservation: Biologists in management and conservation careers are interested in solving environmental problems and preserving the natural world for future generations. Park rangers protect state and national parks, help preserve their natural resources, and educate the general public. Zoo biologists carry out endangered species recovery programs. In addition, management and conservation biologists often work with members of a community such as landowners and special interest groups to develop and implement management plans.

Education: Life science educators enjoy working with people and encouraging them to learn new things, whether in a classroom, a research lab, the field, or a museum.

Colleges and universities: Professors and lecturers teach introductory and advanced biology courses. They may also mentor students with projects and direct research programs.

Secondary school: Teaching younger students requires a general knowledge of science and skill at working with different kinds of learners. Secondary school teachers often specialise in biology and teach other courses of personal interest.

Science museums, zoos, aquariums, parks, and nature centres: Educators in these settings may design exhibits and educational programs, in addition to teaching special classes or leading tours and nature hikes.

New directions in biological careers: There are many careers for biologists who want to combine their scientific training with interests in other fields. Here are some examples:

Biotechnology: Biologists apply scientific principles to develop and enhance products, tools, and technological advances in fields such as agriculture, food science, and medicine.

Forensic science: Forensic biologists work with police departments and other law enforcement agencies using scientific methods to discover and process evidence that can be used to solve crimes.

Business and industry: Biologists work with drug companies and providers of scientific products and services to research and test new products. They also work in sales, marketing, and public relations positions.

Mathematics: Biologists in fields such as bioinformatics and computational biology apply mathematical techniques to solve biological problems, such as modeling ecosystem processes and gene sequencing.

Science writing and communication: Journalists and writers with a science background inform the general public about relevant and emerging biological issues.

Art: All the illustrations in your biology textbook, as well as in newspaper and magazine science articles, were created by talented artists with a thorough understanding of biology.

Human papillomavirus

2010-12-17T00:57:00.001+08:00

Vaccinating 13 year old girls with human papillomavirus vaccine (HPV) can help reduce cases of cervical cancer and genital warts. Studies had shown that teenage girls aged less than 15 have a better immunity response compared with older girls or women.

Immunity among teenagers (15 years and below) vaccinated with HPV is very high even after five and a half years. Free HPV vaccination programme carried out by the government for teenage students was an initiative to prevent cervical cancer. HPV is a common virus that is passed on through genital contact, most often during sex and most sexually active people will get HPV at some time in their lives, though most will never even know it and is most common among people in their late teens and early 20s. Malaysian women were at a high risk of HPV which can led to cervical cancer due to their smoking habits, diet and family history.

According to the World Health Organisation (WHO) 80 percent of women who have reached 50 years would have been affected by HPV and almost 20 percent of them would have reached a chronic stage, resulting in cervical cancer. The government would be spending RM150 million to vaccinate about 300,000 teenagers throughout the country.

A human papillomavirus (HPV) is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in the stratified epithelium of the skin or mucous membranes. While the majority of the nearly 200 known types of HPV cause no symptoms in most people, some types can cause warts (verrucae), while others can – in a minority of cases – lead to cancers of the cervix, vulva, vagina, and anus in women or cancers of the anus and penis in men.

More than 30 to 40 types of HPV are typically transmitted through sexual contact and infect the anogenital region. Some sexually transmitted HPV types may cause genital warts. Persistent infection with "high-risk" HPV types—different from the ones that cause skin warts—may progress to precancerous lesions and invasive cancer. HPV infection is a cause of nearly all cases of cervical cancer; however, most infections with these types do not cause disease.

Most HPV infections in young females are temporary and have little long-term significance. 70% of infections are gone in 1 year and 90% in 2 years. However, when the infection persists—in 5% to 10% of infected women—there is high risk of developing precancerous lesions of the cervix, which can progress to invasive cervical cancer. This process usually takes 15–20 years, providing many opportunities for detection and treatment of the pre-cancerous lesion. Progression to invasive cancer can be almost always prevented when standard prevention strategies are applied - however the lesions still cause considerable burden necessitating preventive surgeries which do in many cases involve loss of fertility.

In more developed countries, a cervical Papanicolaou (Pap) test is used to detect abnormal cells which may develop into cancer. During a colposcopic inspection biopsies can be taken and abnormal areas can be removed with a simple procedure, typically with a cauterizing loop or—more common in the developing world—by freezing (cryotherapy).

Pap smears have reduced the incidence and fatalities of cervical cancer in the developed world, but even so there were 11,000 cases and 3,900 deaths in the U.S. in 2008. Cervical cancer has substantial mortality in resource-poor areas; worldwide, there are 490,000 cases and 270,000 deaths.

HPV vaccines (Cervarix and Gardasil), which prevent infection with the HPV types (16 and 18) that cause 70% of cervical cancer, may lead to further decreases.

Highly sensitive person?

2010-12-12T23:02:00.000+08:00

Are you?

Now, as an introduction to the trait of high sensitivity, see if some of these statements resonate with you, or relate to someone important in your life...

You, your partner, or someone important to you have a heightened awareness of subtleties in your environment, whether it's sight, sound, touch, taste, or smell.
You can become stressed out and upset when overwhelmed and may find it necessary to get away, maybe into a darkened room, to seek solitude, relief and comfort.
You are very creative.
You are very conscientious, hard working, and meticulous, but may become uncomfortable and less efficient or productive when being watched or scrutinised.
You feel compelled to file and organise things and thoughts, also enjoy simplicity and may become overwhelmed or even immobilised by chaos, clutter, or stress.
You are very uncomfortable when feeling things are getting out of your control.
You get a sense of comfort and well being when around a lake, river, stream, the ocean, or even a fountain.
You may experience mood swings, sometimes occurring almost instantly and can also be affected by other people's moods, emotions and problems.
You have a deep, rich, inner life, are very spiritual, and may also have vivid dreams.
You are very intuitive and you feel that you can usually sense if someone isn't telling the truth or if something else is wrong.
You get concerned and think or worry about many things, and have also been told "you take things too personally."
You have had the experience of "cutting people out" of your life.
You were considered quiet, introverted, timid, or shy as a child.

Here are a few more to consider... Can be startled easily. Cautious in new situations. May have trouble sleeping. Extra sensitive to pain. Don't like crowds (unless they are kindred spirits). Avoids violent movies and TV shows. Has a deep respect and appreciation of nature, music and art.

Do some, or many, of these statements ring true for you, your partner, or someone important in your life? If so, you or they may be a highly sensitive person.

Tata....

Scientific Names

2010-12-11T22:11:00.001+08:00

There are many times where you might need to know or write down the scientific name of a plant or an animal. Scientific names allow us to talk about species with a greater degree of accuracy than if we were to just use the common name. Many plants and animals have a more than one common name and so using the correct scientific terms makes talking about plant and animal species less ambiguous.

The scientific name of a species is made up of a combination of two special terms The first name is the genus of the organism and is capitalised, while the second is the species which is not capitalised. Below I will show you the conventions used when writing down a scientific name correctly.

Genus name

The genus name of a species is always written first and it is also underlined (in written) or italicised (only when using computers). Another point to note is that the first letter of the genus name is always capitalised.

in the STPM if students write in italic the scientific names, you'll get 0 mark
students must underline separately; don't underline the whole thing

Species name

The species name of an organism is written second and the specific epithet is always underlined (in written) or italicised (using computers).

Example of a correct scientific names :

Homo sapiens for human

Oryza sativa for paddy

Nephelium lappaceum for rambutan

Once you get to understand the convention then you will find that learning the correct scientific name for a plant or animal is not that hard. By learning the correct scientific names for a plant or animal you will be able to communicate with other scientists around the world unambiguously.

Kingdom : Animalia

Phylum : Chordata

Class           : Mammalia
Order          : Primates
Family         : Hominidae
Genus         : Homo
Species       : sapiens