Non-competitive inhibition lowers Vmax without affecting Km

Steps:

• Recall Michaelis-Menten kinetics: enzyme rate increases hyperbolically with substrate concentration, reaching Vmax at high [S].
• For reversible non-competitive inhibition, inhibitor binds allosteric site, reducing active enzyme, so Vmax decreases but Km (substrate affinity) stays the same.
• Plot rate vs. [S]: uninhibited curve reaches higher Vmax; inhibited curve has same Km (x-intercept) but lower Vmax.
• Select graph with two curves sharing Km but differing in maximum rate.

Why B is correct:

• B shows curves with identical Km (same [S] at half Vmax) but reduced Vmax for inhibited reaction, matching non-competitive inhibition definition.

Why the others are wrong:

• A: Curves show same Vmax but increased Km for inhibition, characteristic of competitive inhibition.
• C: Curves have decreased Km and Vmax, typical of uncompetitive inhibition.
• D: Single curve or no inhibition effect, not showing inhibitor impact.

Final answer: B