Aug 13, 2013
Posted by rozaini at 1:11 AM
Aug 6, 2013
The Two Stages of Photosynthesis
Posted by rozaini at 12:41 AM
Aug 4, 2013
There two main stages :
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.
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.
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
Posted by rozaini at 10:48 AM
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.
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.
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.
Posted by rozaini at 12:53 AM