In an experiment, increasing substrate concentration increases the rate of reaction until it reaches a steady state. At this stage, which of the following changes would most effectively increase the rate of reaction?
Correct answer: C. Increasing enzyme concentration
- A. Increasing substrate concentration
- B. Decreasing temperature
- C. Increasing enzyme concentration
- D. Adding a non-competitive inhibitor
Explanation
Once the rate stops rising with more substrate, all active sites are occupied, so the only way to raise the rate further is to add more enzyme and provide more active sites. Adding substrate has no effect at this point, lowering the temperature slows the reaction and a non competitive inhibitor reduces it.
This question appeared on the UHS MDCAT 2026 paper, which you can sit online with every answer explained.
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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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