IGCSE Biology glossary
Optimum temperature
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Definition
The temperature at which an enzyme works at its fastest rate, producing the maximum amount of product per unit time. For most human enzymes, this is approximately 37 degrees Celsius. Above this temperature, the enzyme begins to denature.
What to include in an exam answer
On enzyme graphs, the optimum temperature is at the peak. Below it, rate increases because molecules have more kinetic energy and collide more often. Above it, rate falls because the active site denatures.
Example in context
Explain why the rate of reaction decreases above 40 degrees C (2 marks): Above the optimum temperature, the enzyme is denatured. The active site changes shape so the substrate can no longer fit, and fewer enzyme-substrate complexes form.
Related syllabus topic
Enzymes