Competitive Inhibition in Enzyme Kinetics

Steps:

• Competitive inhibitors bind to the enzyme's active site, competing with substrate and reducing effective enzyme availability.
• This increases the apparent Km, as more substrate is needed to achieve half of Vmax.
• Vmax remains unchanged, since high substrate concentrations displace the inhibitor and saturate the enzyme.
• Thus, the correct description is Km increases, Vmax unchanged.

Why B is correct:

• By definition, competitive inhibition raises apparent Km in the Michaelis-Menten equation (V = Vmax [S] / (Km + [S])), but Vmax stays the same as excess substrate overcomes inhibition.

Why the others are wrong:

• A: Vmax does not decrease; it is unaffected by competitive inhibitors.
• C: Km increases, not remains the same.
• D: Km increases, so it does not remain the same.

Final answer: B