Factors Affecting Enzyme Activity

This lesson explores the factors that affect the rate of enzyme-catalysed reactions as required by the Edexcel GCSE Combined Science specification (1SC0). You need to explain how temperature, pH and substrate concentration affect enzyme activity, and describe practical investigations to test these factors.

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Overview of Factors

Three main factors affect the rate of enzyme activity:

1. Temperature
2. pH
3. Substrate concentration

Each factor influences how often the enzyme and substrate molecules collide and how well the substrate fits into the active site.

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Factor 1: Temperature

How Temperature Affects Enzyme Activity

As temperature increases from a low value:

• Molecules gain kinetic energy and move faster.
• There are more frequent collisions between enzyme and substrate molecules.
• More enzyme-substrate complexes form per unit time.
• The rate of reaction increases.

At the optimum temperature, the rate of reaction is at its maximum.

Above the optimum temperature: