Why do enzymes denature at high temperatures?
Above the optimum temperature, enzymes denature because the heat breaks the bonds holding the active site’s shape, so the substrate no longer fits.
GCSE Biology
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
In more detail
As temperature rises above the optimum, the enzyme molecules vibrate more and the extra energy breaks the bonds (such as hydrogen and ionic bonds) that hold the enzyme’s tertiary structure together. This changes the shape of the active site, so the substrate can no longer fit — the enzyme is denatured. Fewer enzyme–substrate complexes form, so the rate of reaction falls.
Key points for the exam
- Increased vibration breaks bonds holding the tertiary structure.
- The active site changes shape → substrate no longer fits.
- Denaturation is permanent; the enzyme is not "killed" (it is not alive).
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