Factors Affecting Enzyme Activity

This lesson focuses in depth on the factors that affect enzyme activity and covers Core Practical 3 — investigating the effect of pH on the rate of enzyme activity — as required by the Edexcel GCSE Biology specification (1BI0), Topic 1. You need to be able to describe, explain, and analyse experimental results relating to enzyme function.

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Recap: Key Factors

Three main factors affect the rate of enzyme-controlled reactions:

1. Temperature
2. pH
3. Substrate concentration

Additionally, enzyme concentration can affect the rate, though this is less commonly tested.

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Temperature and Enzyme Activity — In Detail

Below the Optimum Temperature

• At low temperatures, enzyme and substrate molecules have low kinetic energy.
• They move slowly and collide less frequently.
• Fewer enzyme-substrate complexes form per unit time.
• The rate of reaction is slow.

At the Optimum Temperature

• For most human enzymes, the optimum temperature is approximately 37°C.
• Molecules have sufficient kinetic energy to collide frequently.
• The maximum number of enzyme-substrate complexes form per unit time.
• The rate of reaction is at its highest (peak of the graph).

Above the Optimum Temperature