enzyme structure, factors affecting enzyme action, aerobic respiration,enzymes in digestion, speeding up digestion, making use of enzymes

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  • Created by: Anna
  • Created on: 28-11-11 22:34

Enzyme Structure


They are large protiens

They have a particular shape where other molecules can fit in, 'active site'

Too higher temperature = denature/destroyed = change enzyme shape

Catalyse the build up of small molecules into large molecules

Or break down large molecules into small molecules

They lower the amount of energy needed for a reaction to take place - 'activation' energy = reaction happens at a quicker rate

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Factors Affecting Enzyme Action

Reactions are faster when it is warmer

The higher the temperature the more quickly the molecules move and collide with each other

If temp. is too high = denature = changes shape

Enzymes work best in cetain acidic or alkaline conditions not too high = denature

Most enzymes work best at pH 7

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Aerobic Respiration

Respiration Equation:

glucose + oxygen -----> carbon dioxide + water (+energy)

Respiration mainly takes place in the mitochondria

The energy released is used to:

- Build larger molecules from smaller ones

- Enable muscle contraction in animals

- Maitain a constant body temperature in mammels and birds

- Build sugars, nitrates and other nutrients in plants into amino acids and then protiens

Both plants and animals respire!!

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Enzymes in Digestion

Digestion = breakdown of large, insoluble molecules ----> small, soluble molecules

Amylase (carbohydrase):

- Produced by salivary glands, the pancreas and small intestine - work best in alkaline conditions

- Catalyses digestion of starch into sugars in the mouth and small instestine


- Produced by stomach, pancreas and small intestine - best in acidic conditions

- Catalyses breakdown of proteins --> amino acids in stomach and small intestine

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Lipase and Bile


- Produced by pancreas and small intestine

- Catalyses breakdown of lipids (fats and oils) to fatty acids and glycerol

- Work in the small intestine


- It does not contain enzymes

- Emulsifies fats = making it easier for lipase to digest fat molecules

- It is an alkali = it neutralises the acidity caused by stomach acid (small intestine enzymes work best in alkaline conditions)

- Made by the liver ----> stored in the gall bladder ----> works in the small intestine

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Making Use of Enzymes

Protease - Biological washing powders - help remove stains at lower temps.

               - Baby foods - pre-digested proteins

Carbohydrase - convert starch into sugar syrup for foods - cheap, sugar is more valuble e.g. it is an ingredient in sports drinks

Isomerase - convert glucose syrup into fructose syrup in slimming foods - fructose is sweater so less is needed

Invertase - Used to make soft centres in chocolate - expensive

Lipase - Help remove stains in detergents - breakdwon substances in stains into smaller water soluble substances

Strepokinase - Dissolves blood clots in veins and reduces damage - heart attack

Stains include= grass, sweat and food

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Advantages and Disadvantages


- Using enzymes means reactions can be done at normal temps. and pressures

- Money can be saved on energy and expensive equipment

- Enzymes are not used up during reactions, so can often be used again


- Most enzymes are denatured at high temps.

- Often expensive to produce in the first place

- Some people have allergic reactions e.g. rashes to products containing enzymes

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