See how temperature and pH affect enzyme shape and reaction rate
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Enzyme
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Activity rate
100%
Enzyme state
Active
Optimal range
35–40°C, pH 7
Why does enzyme activity drop at very high temperatures?
Lock and key model: Enzymes have a specific active site that fits their substrate like a lock and key.
Temperature and pH affect the shape of this active site. Too hot or too acidic/alkaline causes the enzyme to denature — permanently lose its shape — so it can no longer bind to the substrate.
Most human enzymes work best at body temperature (37°C) and near-neutral pH.