# Explain why maintaining a constant internal body temperature is important for enzyme-controlled reactions in the body.

> WJEC GCSE Biology (Wales) — 2.5.3 Homeostasis · Explain · 4 marks

## Mark scheme (4 marks)

1. Enzymes have an optimum temperature at which they work best
2. If temperature rises above the optimum, the enzyme becomes denatured / the active site changes shape
3. If temperature falls below the optimum, enzyme activity decreases / reactions slow down
4. Maintaining a constant internal temperature keeps enzymes working at or near their optimum, so metabolic reactions proceed at the correct rate

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](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-maintaining-a-constant-internal-d1fc7306) · Published by Druglandscape Ltd.