IGCSE Biology glossary
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Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
The specific region on an enzyme molecule where the substrate binds. The shape of the active site is complementary to the shape of the substrate, which is why each enzyme only catalyses one reaction.
What to include in an exam answer
The active site is 'complementary' to the substrate. After denaturation, the active site changes shape so the substrate can no longer fit. Use these two points together in denaturation answers.
Example in context
Explain what happens to the active site at very high temperatures (2 marks): The high temperature causes the active site to change shape permanently (denature), so the substrate can no longer fit and the reaction stops.
Related syllabus topic
Enzymes