Aug 13, 2013

Feeling depressed??

Here are 10 ways to detect depression early and let the healing begin.

1. You are over-confident and fearless.
Many people–and especially high achievers–cope with depression by acting in ways opposite to how they feel. (called as “escapism.”) Engaging in daredevil pursuits, be it  mounting a takeover of a rival company or quitting your job to open a restaurant, makes you  feel invincible, when you’re really in the dumps. There is a method to this madness: The major cause of depressions–those not born of biochemical imbalances, of which there are plenty–is feeling out of control or helpless. Achievers loathe that feeling and fight like hell to deny it through action. But that, ultimately, won’t work.

2. You’ve gone from one drink with dinner to three before appetizers.
“Alcohol is the anesthesia by which we endure the operation of life.” Bernard Shaw’s observation is as true now as it was then. Drinking alcohol is the most common tactic people take to self-medicate emotional pain. The problem with this strategy is that when you finally recognise the pain driving you to drink, you’ll have two disorders to contend with rather than one.

3. You’re obsessed with achievement in bed.
Have a limp libido? Going on a Hugh-Hefner-like tear may not lift your spirits.  If you find you’ve traded serial monogamy for seducing any partner that will have you, there is a good chance you’re trying to keep depression at bay.

4. Conflicts quickly escalate into fights.
One common but exceedingly dumb way to dull the feeling of helplessness brought on by depression is to show people you’re nobody’s patsy. Get cut off on the highway? Run the bastard off the road. Have an idea shot down at a brainstorming session? Take the opinionated punk outside and pummel him. If you’re lucky, maybe you’ll have enough bruises to distract you from your emotional pain.

5. You feel nothing.
Rather than be sad, many people would choose to forgo feeling altogether. But some people end up getting stuck in neutral–dooming them to invite the same pain again and again. Worse, this zombie-like approach creates anxiety in those around you and alienates those who care for you.

6. You can’t stop socialising.
Immersing yourself in group activities sounds healthy–and for many people it is. However, if the sole purpose is to keep you from wrestling with your thoughts and feelings, having a brimming social calendar is not the answer (and you probably won’t be all that fun a companion anyway). Like the toxic mortgage securities still stinking up bank balance sheets, you have to flush out the dreck before you can start investing anew.

7. You can’t concentrate.
Everyone suffers from scattered thoughts now and again. Those who are depressed but who possess too much control to act out recklessly may do so in fantasy. But how to distinguish a healthy daydream from potentially dangerous ones? Healthy dreams involve changes in your life that you can realise in a handful of steps. Unhealthy ones take you from middle-class to movie-stardom overnight.

8. You have trouble accepting praise or goodwill.
Martin Seligman, the psychologist who revolutionised the thinking about depression, studied the behaviour of dogs that were given electric shocks. Eventually, they would lay helplessly in their cages, not responding to tugs on their leashes that would have moved them to safety from the shocks. The human corollary: If you find yourself ignoring favourable gestures or simple interpersonal warmth, chances are you’re not a malcontent. You’re depressed.

9. You work harder, not smarter.
When people are depressed, they have trouble seeing novel solutions to their problems. Instead, they do more of the same. The classic example is trying to exercise your way to happiness: If you already log a few hours a week at the gym, spending another 30 more minutes every day may briefly lift your spirits. But that relief is ephemeral. When it dissipates, get off the treadmill and get to the root of what’s bothering you.

10. You laugh and cry at times that don’t call for it. 
In psychiatry, the concept “inappropriate affect” refers to behaviour that is emotionally out of sync with the stimulus that prompted it. People who are depressed but do not know it exhibit a unique variant of this problem: They over-react to insignificant sadness, and ignore major league bad news.
This flavour of depression, a stepchild of alexithymia which causes a gross lack of appropriate feelings, can really make you feel out-of-control. 

Aug 6, 2013

Photosynthesis (Higher Level)

The Two Stages of Photosynthesis

The equation for photosynthesis is a deceptively simple summary of a very complex process. Actually, photosynthesis is not a single process, but two processes, each with multiple steps. These two stages of photosynthesis are known as the light reactions (the photo part of photosynthesis) and the Calvin cycle (the synthesis part).
The diagram above is an overview of photosynthesis: cooperation of the light reactions and the Calvin cycle. In the chloroplast, the thylakoid membranes are the sites of the light reactions, whereas the Calvin cycle occurs in the stroma. The light reactions use solar energy to make ATP and NADPH, which function as chemical energy and reducing power, respectively, in the Calvin cycle. The Calvin cycle incorporates CO2 into organic molecules, which are converted to sugar.

The light reactions are the steps of photosynthesis that convert solar energy to chemical energy. Light absorbed by chlorophyll drives a transfer of electrons and hydrogen from water to an acceptor called NADP+ (nicotinamide adenine dinucleotide phosphate), which temporarily stores the energised electrons. Water is split in the process, and thus it is the light reactions of photosynthesis that give off O2 as a by–product. The electron acceptor of the light reactions, NADP+, is first cousin to NAD+, which functions as an electron carrier in cellular respiration; the two molecules differ only by the presence of an extra phosphate group in the NADP+ molecule. The light reactions use solar power to reduce NADP+ to NADPH by adding a pair of electrons along with a hydrogen nucleus, or H+. The light reactions also generate ATP, using chemiosmosis to power the addition of a phosphate group to ADP, a process called photophosphorylation. Thus, light energy is initially converted to chemical energy in the form of two compounds: NADPH, a source of energised electrons (“reducing power”), and ATP, the versatile energy currency of cells. Notice that the light reactions produce no sugar; that happens in the second stage of photosynthesis, the Calvin cycle.

The Calvin cycle is named for Melvin Calvin, who, along with his colleagues, began to elucidate its steps in the late 1940s. The cycle begins by incorporating CO2 from the air into organic molecules already present in the chloroplast. This initial incorporation of carbon into organic compounds is known as carbon fixation . The Calvin cycle then reduces the fixed carbon to carbohydrate by the addition of electrons. The reducing power is provided by NADPH, which acquired energized electrons in the light reactions. To convert CO2 to carbohydrate, the Calvin cycle also requires chemical energy in the form of ATP, which is also generated by the light reactions. Thus, it is the Calvin cycle that makes sugar, but it can do so only with the help of the NADPH and ATP produced by the light reactions. The metabolic steps of the Calvin cycle are sometimes referred to as the dark reactions, or light–independent reactions, because none of the steps requires light directly. Nevertheless, the Calvin cycle in most plants occurs during daylight, for only then can the light reactions provide the NADPH and ATP that the Calvin cycle requires. In essence, the chloroplast uses light energy to make sugar by coordinating the two stages of photosynthesis.

The thylakoids of the chloroplast are the sites of the light reactions, while the Calvin cycle occurs in the stroma. In the thylakoids, molecules of NADP+ and ADP pick up electrons and phosphate, respectively, and then are released to the stroma, where they transfer their high–energy cargo to the Calvin cycle. The two stages of photosynthesis are treated in this figure as metabolic modules that take in ingredients and crank out products. Our next step toward understanding photosynthesis is to look more closely at how the two stages work, beginning with the light reactions.
The light reactions convert solar energy to the chemical energy of ATP and NADPH.

Chloroplasts are chemical factories powered by the sun. Their thylakoids transform light energy into the chemical energy of ATP and NADPH. To understand this conversion better, we need to know about some important properties of light.
Chlorophyll and light absorption
Chlorophyll absorbs light from the visible part of the electromagnetic spectrum. Chlorophyll is made up of a number of different pigments: chlorophyll a, chlorophyll b, chlorophyll c along with other pigments such as carotenoids. Each of these absorb different wavelengths of light so that the total amount of light absorbed is greater than if a single pigment were involved. Not all wavelengths of light are absorbed equally. An absorption spectrum is a graph showing the percentage absorption plotted against wavelength of light (Fig 1). An action spectrum is a graph showing the rate of photosynthesis plotted against wavelength of light (Fig 1). The similarity between the absorption spectrum and the action spectrum shows that red (650- 700nm) and blue (400-450nm) wavelengths, which are absorbed most strongly, are also the wavelengths which stimulate photosynthesis the most. Green light (550mm) is mostly reflected.

1. Light energy is absorbed by chlorophyll molecules in PSI and PSII.
2. The electrons in the chlorophyll molecules are boosted to a higher energy level and are emitted.
3. The loss of electrons from PSII stimulates the loss of electrons from water i.e. it stimulates the splitting or photolysis of water. O2 is given off.
4. The electron from PSII passes through a series of electron carriers. At each transfer some energy is released.
5. This energy is used by cytochromes to pump protons (H+ ions) from the stroma across the thylakoid membranes. This sets up an electrochemical or H+ gradient. The H+ ions then diffuse back through a protein which spans the thylakoid membrane. Part of this protein acts as an enzyme - ATP synthetase - which uses the diffusion of H+ to synthesise ATP.
6. The electrons emitted from PSI may:
a) Pass down through the same carrier molecules as the electrons from PSII, again generating ATP. Before returning to PSI. Thus electrons are cycled (PSI i carriers i PSI i carriers etc. The energy to begin this cycle came from light (photo) and is used to convert ADP to ATP i.e. to phosphorylate ADP (add a phosphate). Hence this process is called cyclic photophosphorylation (CPP). Or
b) Combine with the hydrogen ions (protons) released from the photolysis of water to reduce nicotinamide adenine dinucleotide phosphate (NADP), forming NADPH. Non cyclic photophosphorylation (NCP) occurs when electrons are emitted from water and then pass to PSII i carrier (with ATP production) i PSI i carriers i NADPH.
7. Reactions 1-6 make up the Light Dependent Stage. The ATP and NADPH produced diffuse into the stroma where the Light Independent Stage occurs (7-11).
8. CO2 combines with a 5C compound called ribulose bisphosphate. This reaction is catalysed by the enzyme RuBPC.
9. The 6C compound formed immediately splits into two molecules of glycerate-3-phosphate (GP).
10. The GP molecules are converted into molecules of triose phosphate (TP) using energy from ATP and the hydrogen atom from NADPH i.e. the two useful products of the LDS are now used up in the LIS.
11. Some of the TP is used to regenerate RuBP.
12. The rest of the TP is used to produce other essential substances which the plant needs - fats, proteins etc.

Aug 4, 2013

Photosynthesis (SPM Level)

Photosynthesis – takes place in the chloroplast
There two main stages :  

i) light reaction and 
ii) 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 a series of reactions catalysed by photosynthetic enzymes.
Carbon dioxide is reduced into glucose.
Glucose monomers undergo condensation to form starch which will stored temporarily as starch grains in the chloroplast.
Light reaction - occurs in the grana (that 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 amino acids and fatty acids

Biology Workshop (SMK Raja Tun Uda, Penang)

Biology Workshop (SMK Tunku Abdul Malik)

Biology Workshop (SMK Chepir, Sik)

Studying for Bio Exam

Biology exams can seem intimidating and overwhelming to biology students. The key to overcoming these obstacles is preparation. By learning how to study for biology exams you can conquer your fears. Remember, the purpose of an exam is for you to demonstrate that you understand the concepts and information that have been taught. Below are some excellent tips to help you learn how to study for biology exams. 

Here's How:   
Get Organised
An important key for success in biology is organisation. Good time management skills will help you to become more organised and waste less time preparing to study. Items such as daily planners and calendars will help you to know what you need to do and when you need to have it done. 
Start Studying Early  It is very important that you start preparing for biology exams well in advance. I know, I know, it is almost tradition for some to wait until the last minute, but students who implore this tactic don't perform their best, don't retain the information, and get worn out.  
Review Notes  
Be sure that you review your notes before the exam. You should start reviewing your notes on a daily basis. This will ensure that you gradually learn the information over time and don't have to cram.  
Review the Biology Text 
Your biology textbook and the reference book are wonderful sources for finding illustrations and diagrams that will help you visualise the concepts you are learning. Be sure to reread and review the appropriate chapters and information in your textbook/reference book. You will want to make sure that you understand all key concepts and topics.  
Get Answers To Your Questions 
If you are having difficulty understanding a topic or have unanswered questions, discuss them with your teacher. You don't want to go into an exam with gaps in your knowledge. 
Quiz Yourself 
To help prepare yourself for the exam and find out how much you know, give yourself a quiz. You can do this by using prepared flash cards or taking a sample test. You can also use online biology games and quiz resources.  
Find a Study Buddy 
Get together with a friend or classmate and have a study session. Take turns asking and answering questions. Write your answers down in complete sentences to help you organise and express your thoughts.  
Attend a Review Session 
If your teacher holds a review session, be sure to attend. This will help to identify specific topics that will be covered, as well as fill in any gaps in knowledge. Help sessions are also an ideal place to get answers to your questions.  
Now that you have followed the previous steps, it's time to rest and relax. You should be well prepared for your biology exam. It's a good idea to make sure you get plenty of sleep the night before your exam. You have nothing to worry about because you are well prepared.

Good luck....

Aug 1, 2013

Double fertilisation in angiosperm

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 sperms. 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.