This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
When an enzyme is competitively inhibited, which of the following changes occur? 
Select and explain. 
A. The apparent Km is unchanged., B. The apparent Km is decreased., C. Vmax is decreased., D. Vmax is unchanged.
D: Vmax is unchanged.
Answer: D: Vmax is unchanged. 
Explanation: Features of noncompetitive inhibition:

Inhibitor have no structural resemblance to substrate.
Most irreversible (Except a few reversible non-competitive inhibition).
Excess substrate do not abolish the inhibition.
Km remains the same.
Vmax decreases.

 
Features of competitive inhibition:

Inhibitor will be structural analogue of substrate.
Reversible 
Excess substrate abolish the inhibition.
Km increases.
Vmax remains the same.