Enzymes and Digestion

Enzymes are biological catalysts that speed up chemical reactions in living organisms. In this lesson you will learn about enzyme structure and function, the factors that affect enzyme activity, the specific digestive enzymes required by the AQA GCSE Combined Science Trilogy specification (8464), and the required practical on food tests.

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What Are Enzymes?

Enzymes are large protein molecules that act as biological catalysts. A catalyst is a substance that speeds up a chemical reaction without being used up or changed in the process.

Key facts about enzymes:

• They are produced by living cells
• They are specific — each enzyme catalyses only one type of reaction
• They work by lowering the activation energy required for a reaction to take place
• They are not used up in the reaction and can be reused

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The Lock and Key Model

Enzymes work because of their specific three-dimensional shape. Each enzyme has a region called the active site, which has a unique shape that only the correct substrate (the molecule the enzyme acts on) can fit into — just like a key fits into a lock.