Question
| A. |
T Km |
| B. |
Km |
| C. |
T Vmax |
| D. |
No change in Km and Vmax |
|
Correct Answer » A Explanation |
 |
Clinical Reasoning for the Correct Answer
– Competitive inhibitors bind reversibly to the active site of the enzyme, competing with the substrate.
– This competition raises the substrate concentration needed to reach half of Vmax, increasing Km.
– Vmax remains unchanged because inhibition can be overcome by increasing substrate concentration.
Why Option A is Correct
– Competitive inhibition increases Km, indicating decreased enzyme affinity for substrate due to competition.
– The inhibitor does not affect the catalytic function; hence, Vmax stays the same.
Why Option B is Incorrect
– Km decreases only when enzyme affinity increases, which does not occur in competitive inhibition.
– Competitive inhibitors make substrate binding harder, increasing Km instead.
Why Option C is Incorrect
– Vmax is unaffected in competitive inhibition, as sufficient substrate outcompetes the inhibitor.
– Increased Vmax is not a feature of competitive inhibition.
Why Option D is Incorrect
– Competitive inhibition changes Km but not Vmax; no effect on both parameters is incorrect.
– “No change” applies only rarely, such as in non-competitive inhibition with unaffected Km, but not here.
