# Explain why an increase in temperature from 10°C to the optimum temperature increases the rate of an enzyme-controlled reaction, and what happens to the enzyme if the temperature is increased well above the optimum.

> WJEC A-Level Biology (Wales) — 1.1 Chemical elements and biological molecules · Explain · 5 marks

## Mark scheme (5 marks)

1. Increasing temperature gives molecules more kinetic energy
2. Molecules move faster, so more successful collisions occur between enzyme and substrate
3. More enzyme-substrate complexes form, increasing the rate of reaction
4. At temperatures well above the optimum, the enzyme becomes denatured
5. Denaturation causes a permanent change in the shape of the active site, so the substrate can no longer fit and no enzyme-substrate complexes can form

## Key terms

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

## Related

- [Revision notes for WJEC A-Level 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-an-increase-in-temperature-2ce723b1) · Published by Druglandscape Ltd.