AQA Additional Science Biology - Enzymes

Taken from the AQA Science Revision Guide, just thought I'd share it on here anyway :)

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  • Created on: 28-04-12 11:32
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B2.4 Enzymes
4.1 Enzyme Structure
Enzymes are biological catalysts ­ they speed up reactions.
Enzymes are large proteins and each has a particular shape. This shape has an area where
other molecules can fit in. This area is called `active site'.
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 breakdown of
large molecules into small molecules.
Enzymes lower the amount of energy necessary for a reaction to take place ­ the `activation'
Key Points
The structure of an enzyme allows certain molecules to fit.
If this structure is changed (the enzyme is denatured) then the enzyme cannot work as a

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B2.4 Enzymes
4.2 Factors affecting Enzyme Action
Reactions take place faster when it is warmer. At the higher temperature the molecules move
around more quickly so collide with each other more often and with more energy.
However, if the temperature gets too hot the enzyme stops
working. That's because the active site changes shape
and the enzyme becomes denatured.
Enzymes work best in certain acidic or alkaline conditions
(pH).…read more

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B2.4 Enzymes
4.3 Aerobic Respiration
The equation for respiration is:
Glucose + Oxygen Carbon Dioxide + Water [+Energy]
C6H12O6 + 6O2 6CO2 + 6H2O + energy
The process takes place in the mitochondria.
The energy released is used to:
Build larger molecules from smaller ones
Enable muscle contraction in animals
Maintain a constant body temperature in mammals and birds
Build sugars, nitrates and other nutrients in plants into amino acids and then proteins.…read more

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B2.4 Enzymes
4.4 Enzymes in Digestion
Digestion involves the breakdown of large, insoluble molecules into smaller soluble ones.
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 the small intestine.…read more

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B2.4 Enzymes
4.5 Speeding up Digestion
Protease enzymes in the stomach work best in acid conditions. Glands in the stomach
wall produce hydrochloric acid to create very acidic conditions.
Amylase and lipase work in the small intestine. They work best when then conditions are
slightly alkaline.
The liver produces bile that is stored in the gall bladder. Bile is squirted into the small
intestine and neutralises the stomach acid.…read more

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B2.4 Enzymes
4.6 Making use of Enzymes
Biological washing powders contain enzymes that digest food stains. They work at lower
temperatures than ordinary washing powders so can save us money.
We can also use:
Protease enzymes to predigest proteins in some baby foods
Isomerases to convert glucose into fructose. Fructose is much sweeter, so less is
needed in foods. The foods, therefore, are not so fattening.
Carbohydrases to convert starch into sugar syrup for use in foods.…read more


lisa linsdell

Taken from the AQA revision guide, key words and terms highlighted. Useful key points to help summarize the information.


It was so great, I just wanted to bungee jump without the rope.


looool @SirSnazza

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