Enzymes and Digestion

Enzymes are biological catalysts produced by living organisms. They speed up chemical reactions in the body without being used up themselves. In AQA GCSE Biology, understanding how enzymes work — and how they are involved in digestion — is essential. This lesson covers the structure and function of enzymes, factors affecting enzyme activity, and the specific digestive enzymes you need to know.

---

What Are Enzymes?

An enzyme is a large protein molecule that acts as a biological catalyst. A catalyst is a substance that speeds up a chemical reaction without being changed or used up in the process. Enzymes are produced inside living cells and control all the metabolic reactions in the body.

Key Properties of Enzymes