# Explain why enzymes stop working when the temperature is increased above their optimum temperature.

> Edexcel GCSE Biology (1BI0) — 1.4 Enzymes · Explain · 4 marks

> Enzymes are biological catalysts that speed up chemical reactions in living organisms. Each enzyme has an optimum temperature at which it works best.

## Mark scheme (4 marks)

1. The enzyme has an active site with a specific shape
2. Above the optimum temperature, the bonds holding the enzyme's shape break / are disrupted
3. The shape of the active site changes / the enzyme is denatured
4. The substrate can no longer fit into / bind to the active site, so the reaction cannot be catalysed

## Key terms

- [optimum temperature](https://www.gradenine.co.uk/glossary/optimum-temperature)

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-enzymes-stop-working-when-765247c1) · Published by Druglandscape Ltd.