# Explain why enzymes are described as biological catalysts and outline how an enzyme's structure is related to its function.

> AQA A-Level Biology (7402) — 3.1.4 Proteins and Enzymes · Explain · 5 marks

## Mark scheme (5 marks)

1. Enzymes speed up (the rate of) chemical reactions
2. Enzymes are not used up / consumed in the reaction (so can be reused)
3. Enzymes are proteins (made of amino acids / chains of amino acids)
4. Each enzyme has a specific / uniquely shaped active site
5. The substrate fits into the active site (because its shape is complementary to the active site) forming an enzyme-substrate complex

## Key terms

- [biological catalyst](https://www.gradenine.co.uk/glossary/biological-catalyst)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-enzymes-are-described-as-32aec8f1) · Published by Druglandscape Ltd.