Enzyme Activity in a Fever
A student investigates how temperature affects an enzyme that breaks down hydrogen peroxide. At 25°C the reaction produces gas steadily. At 37°C the rate is higher. At 60°C the rate drops sharply within minutes and then stops. The student concludes that the enzyme was 'used up' by the reaction and that higher temperature always increases enzyme activity. A classmate points out that the human body fights infection with fever and asks whether a fever of 40°C could stop this enzyme from working. The enzyme is known to have an optimum near 37°C.
1. Explain why the rate falls at 60°C even though the enzyme is not 'used up.'
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Enzymes are proteins whose shape depends on weak interactions. At 60°C, thermal energy disrupts these interactions and the enzyme denatures, losing the active-site shape that binds substrate. Denaturation is not the same as being consumed; the enzyme molecules are still present but nonfunctional. The initial rise from 25°C to 37°C reflects more frequent collisions and higher kinetic energy, which is why the rate increases toward the optimum. Beyond the optimum, denaturation outpaces the collision effect, so the rate collapses. The judgement is to distinguish temporary rate changes from irreversible loss of structure.
2. Would a 40°C fever stop this enzyme? Use the data to reason.
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No-40°C is only slightly above the 37°C optimum, so activity would likely be somewhat reduced but not abolished. The sharp drop occurred at 60°C, far above body temperature, where denaturation becomes rapid. A fever of 40°C may slow the enzyme modestly, but it would not stop it, and the body's fever response is not designed to shut down this enzyme. The student's claim that 'higher temperature always increases activity' is also wrong: activity rises to an optimum and then falls. The reasoning is to use the observed optimum and the 60°C collapse to predict behavior at an intermediate temperature.