# Catalase is an enzyme found in liver cells that breaks down hydrogen peroxide into water and oxygen. Explain how the structure of catalase allows it to act as a biological catalyst, and describe what happens to the enzyme when it is boiled.

> Eduqas A-Level Biology — 1.4 Biological reactions and enzymes · Explain · 5 marks

## Mark scheme (5 marks)

1. Catalase is a protein made from chains of amino acids that fold to give it a specific shape
2. Catalase has an active site with a shape complementary to the hydrogen peroxide substrate
3. The substrate (hydrogen peroxide) enters the active site to form an enzyme-substrate complex
4. The enzyme is not changed / is released unchanged and can be reused / acts repeatedly
5. Boiling causes denaturation — the shape of the active site changes permanently so no enzyme-substrate complexes can form and the rate of reaction decreases / stops

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/catalase-is-an-enzyme-found-in-9e7161da) · Published by Druglandscape Ltd.