AQA GCSE Biology Unit 2 Enzymes

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  • Created by: chowmein
  • Created on: 13-05-13 16:51

What are Enzymes?

Enzymes are biological catalysts, they increase the rate of reaction.

They are made up of protein molecules (these are long chains of amino acids).

The active site is the area in which the substrate (the thing to be broken down) link to form the enzyme-substrate complex (the place where the stuff happens).

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Limiting Factors of Enzymes

Temperature - too high and the enzyme will denature (stop working because the active site becomes the wrong size).

pH - this is best aroung 8 for most enzymes, slightly alkaline.

Enzymes can be used for respiration, photosynthesis and protein synthesis.

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Aerobic - glucose + oxygen ---> carbon dioxide + water +energy

Anaerobic - glucose ---> lactic acid + little energy

Respiration is used for energy which is used for movement, sex, heating and basic cell functions.

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Digestive Enzymes

Amylase - made in the salivary glands and the pancreas.

  • It breaks down carbohydrates into sugars e.g. glucose.
  • In the mouth and small intestine.

Protease - made in the pancreas and small intestine

  • Released in the small intestine and stomach.
  • Break down proteins into amino acids

Lipase - made in the pancreas and small intestine

  • Breaks down fats into fatty acids and glycerol.
  • Released in the small inestine.

There are also enxymes in the ribosomes which catalyse the making of proteins from amino acids.

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Uses of Enzymes


  • Used in baby food to pre-digest some of the protein so a baby can have it.


  • Starch into sugar
  • Make glucose syrup.
  • Isomerase can break down glucose syrup into fructose syrup which is sweeter than glucose so less can be used.

Biological Detergents

  • Contain lipases and proteases
  • Break down stains that have biological substance in.
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