Which type of enzyme inhibitor does not affect the maximal velocity of a reaction?

Question

BlackTom AI · Accepted Answer

Competitive inhibitors bind reversibly to the enzyme’s active site, competing with substrate; this raises the apparent Km but leaves Vmax unchanged.

Relevant concepts:
- Michaelis–Menten kinetics: v = Vmax [S] / (Km + [S]).
- Competitive inhibition modifies Km (making it larger) but not Vmax.
- Other inhibitor types (noncompetitive, uncompetitive, irreversible/covalent) change Vmax.

Step-by-step reasoning with equations:
1. For a competitive inhibitor the rate equation becomes
   v = Vmax [S] / (Km (1 + [I]/Ki) + [S]),
   where [I] is inhibitor concentration and Ki is the inhibitor dissociation constant.
2. Define Km,app = Km (1 + [I]/Ki). Then v = Vmax [S] / (Km,app + [S]).
3. Take the high-substrate limit ([S] → ∞): v → Vmax because the [S] term dominates the denominator. Thus Vmax is unchanged by competitive inhibition.
4. On a Lineweaver–Burk plot (1/v vs 1/[S]) competitive inhibitors increase the slope and shift the x-intercept (−1/Km) but all lines intersect at the same y-intercept (1/Vmax), reflecting unchanged Vmax.

Why the correct answer is correct:
- Because a competitive inhibitor can be outcompeted by high substrate concentrations, the maximum catalytic rate achievable (Vmax) remains the same; only the substrate concentration needed to reach half Vmax (Km) increases.

Why the other options are incorrect:
- Uncompetitive inhibitor: binds only to ES complex, decreasing both Vmax and Km (so Vmax is affected).
- A toxin which covalently modifies the enzyme (irreversible inhibitor): reduces the concentration of active enzyme and therefore lowers Vmax.
- Noncompetitive inhibitor: reduces Vmax (by lowering effective active enzyme) while Km typically remains unchanged.

Conclusion: The correct choice is "A competitive inhibitor," which matches the provided answer.

Which type of enzyme inhibitor does not affect the maximal velocity of a reaction?单项选择题

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How does a competitive inhibitor affect Km and Vmax ?

Which of the following sentences best describes what happens during competitive inhibition of an enzyme?

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Which type of enzyme inhibitor does not affect the maximal velocity of a reaction?单项选择题

类似问题

How does a competitive inhibitor affect Km and Vmax ?

Which of the following sentences best describes what happens during competitive inhibition of an enzyme?

A competitive inhibitor of an enzyme:

A competitive inhibitor of an enzyme:

This type of inhibition is _______________. We know because __________________. In this type of inhibition, ___________ is forbidden.

9. This figure describes inhibition of an enzyme by ____________________.

Which of the following is NOT correct about a competitive inhibitor of an enzyme?

更多留学生实用工具

希望你的学习变得更简单

This type of inhibition is ___. We know because . In this type of inhibition, _ is forbidden.