AQA GCSE Biology 2

I made these notes for my B2 revision, they're pretty much the same as the AQA GCSE Biology revision guide, but I made them so it was easier to understand in a format that I responded to. Hope this helps anyone with upcoming exams and hope its useful :-)

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  • Created by: antiana
  • Created on: 19-05-11 09:07
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B2 AQA GCSE Biology
Chapter One : Cells
Animal and plant cells have structures that enable them to function and do their jobs.
Plant cells have some structures that you will not find in an animal cell.
A nucleus (the brain of the cell) is used to control the cell's activity
Cytoplasm where many chemical reactions take place
A cell membrane that controls the movement of materials
Mitochondria where energy is released during aerobic respiration
Ribosomes where proteins are made (synthesised).
Plant cells also have;
A rigid cell wall for support
Chloroplasts that also contain chlorophyll for photosynthesis
A permanent vacuole containing cell sap.
1 | Biology Unit 2

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When an egg is fertilised, it begins to grow and develop.
At first, there's just a growing ball of cells. Then as the organism gets bigger, some of the cells
change and become specialised.
Some e.…read more

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Molecules move randomly because of the energy they have.
Diffusion is the random movement of molecules from an area of high concentration to an area
of lower concentration.
The larger the difference in concentration, the fast the rate of diffusion.
E.…read more

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Chapter Two : How plants produce food
The equation for photosynthesis is
carbon dioxide + water (+ light energy) glucose + oxygen
Carbon dioxide taken in by leaves. Water taken up by roots.
Chlorophyll traps the energy needed for photosynthesis.
Glucose (a carbohydrate) is produced; oxygen is given off as a waste gas.
Photosynthesis can only be carried out by green plants.
Guard cells open and close stomata to control water loss. The stomata allows gases to move in and out
of the leaf.…read more

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If there is too little CO2, then the rate will SLOW DOWN. May be limited in enclosed spaces, e.g. in a
greenhouse on a sunny day or in a rapidly photosynthesising rain forest.
When growing plants, there is no point increasing one of these factors if the photosynthesis is still
limited by another one. This would just waste money.
Product of photosynthesis is GLUCOSE which is used for respiration.
Glucose is also combined with other nutrients (mineral ions) by the plant to form new materials.…read more

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Organism Number Biomass ­ dry mass in g
Oak tree 1 500,000
Aphids 10,000 1,000
Ladybirds 200 50
Pyramid of numbers Pyramid of biomass
You can draw pyramids of biomass to scale to give an even more accurate picture.
Not all of the food eaten can be digested, so energy is lost in faeces (waste materials).
Some of the energy is used for respiration, which releases energy for living processes.…read more

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Keeping the animal at a warmer temperature so it doesn't use as much energy from food to
keep itself at a constant temperature
Detritus feeders (such as some types of worm) may start the process of decay by eating dead animals or
plants and producing waste materials. Decay organisms then break down the waste and dead plants and
Decay organisms are microorganisms (bacteria and fungi). Decay is faster if it is warm and wet.…read more

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Too high a temperature will change the enzymes shape, and it will no longer work. We say it has been
destroyed or denatured.
Enzymes can catalyse the build up of small molecules into large molecules or the break down of large
molecules into small molecules.
Enzymes lower the amount of energy necessary for a reaction to take place ­ the activation energy.
Reactions take place faster when it is warmer.…read more

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Amylase (a carbohydrase) is produced by the salivary glands, the pancreas and the small
intestine. Amylase catalyses the digestion of starch into sugars in the mouth and small intestine.
Protease is produced by the stomach, the pancreas and the small intestine. Protease catalyses
the breakdown of proteins into amino acids in the stomach and small intestine.
Lipase is produced by the pancreas and small intestine. Lipase catalyses the breakdown of lipids
(fats and oils) to fatty acids and glycerol.…read more

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Chapter Five : Homeostasis
The processes in your body that help to maintain a constant internal environment are known as
Just think of the different temperatures we experience:
Your body also has to cope with varying rates of respiration needed in different activities:
Carbon dioxide is a waste product of respiration, it is excreted through the lungs
Some of the amino acids we take in are not used. They are converted into urea by the liver and
excreted by the kidneys in the urine.…read more


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