A Levels Biology (9700)•9700/13/M/J/20
Explanation
Temperature effect on human enzyme activity
Steps:
- Human enzymes function optimally at 37°C, the body temperature.
- Experiment X holds temperature constant at 37°C, maintaining peak activity.
- Experiment Y raises temperature to 40°C, exceeding the optimum slightly.
- This causes enzyme denaturation, reducing reaction rate in Y compared to X.
Why A is correct:
- Graph A depicts steady high activity in X and a drop in Y, aligning with enzyme denaturation above optimal temperature per the temperature-activity curve.
Why the others are wrong:
- B shows rising activity in Y, contradicting denaturation's inhibitory effect.
- C indicates identical activity in both, ignoring temperature's impact on structure.
- D displays decline in X, but 37°C is optimal, not denaturing.
Final answer: A
Topic: Factors that affect enzyme action
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