# Explain how temperature affects the rate of an enzyme-controlled reaction, including what happens at temperatures above the optimum.

> AQA A-Level Biology (7402) — 3.1.4 Proteins and Enzymes · Explain · 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, so enzyme and substrate collide more frequently / more enzyme-substrate complexes form
3. Above the optimum temperature, the rate of reaction decreases
4. The enzyme becomes denatured — bonds holding the tertiary structure break / the shape of the active site changes
5. The substrate can no longer fit into the active site, so no enzyme-substrate complex can form / the enzyme can no longer catalyse the reaction

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-temperature-affects-the-rate-a0e09935) · Published by Druglandscape Ltd.