Above its optimum temperature the rate of an enzyme catalysed reaction falls sharply because the enzyme
Correct answer: B. is denatured as its tertiary structure breaks down
- A. is used up by the reaction
- B. is denatured as its tertiary structure breaks down
- C. becomes a substrate itself
- D. loses its active site to the product
Explanation
Heat breaks the hydrogen bonds and other weak interactions holding the tertiary structure, so the active site loses its shape and can no longer bind the substrate. This is denaturation and it is usually irreversible, which is why the curve falls steeply rather than plateauing. Enzymes are catalysts, so they are recovered unchanged and are never used up.
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About Factors Affecting Enzyme Action
Enzyme activity changes with temperature, pH, substrate concentration and enzyme concentration because these factors affect molecular collisions and the active site. Questions also examine optimum conditions, denaturation and inhibition, while distinguishing a fall in activity caused by unsuitable conditions from permanent enzyme damage.
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