# Describe how temperature affects the rate of an enzyme-controlled reaction, including what happens both below and above the enzyme's optimum temperature.

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

## Mark scheme (5 marks)

1. As temperature increases up to the optimum, the rate of reaction increases
2. Because molecules have more kinetic energy and move faster, leading to more successful collisions / more enzyme-substrate complexes forming
3. At the optimum temperature the rate of reaction is at its maximum / fastest
4. Above the optimum temperature the enzyme becomes denatured / the active site changes shape
5. Denaturation means the substrate can no longer fit into the active site, so no enzyme-substrate complexes form and the rate of reaction decreases

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-temperature-affects-the-rate-e8534811) · Published by Druglandscape Ltd.