Michaelis-Menten Kinetics and Inhibition
Enzyme kinetics is one of the highest-yield advanced topics in the MCAT B/B section. The Michaelis-Menten equation describes reaction velocity: V = (Vmax Γ [S]) / (Km + [S]). Km is the substrate concentration at which V = Vmax/2 β a measure of enzyme-substrate affinity (lower Km means higher affinity). Vmax is the maximum velocity when all enzyme active sites are saturated. On a double-reciprocal (Lineweaver-Burk) plot, the y-intercept = 1/Vmax, the x-intercept = -1/Km, and the slope = Km/Vmax. Competitive inhibitors increase apparent Km without changing Vmax (the inhibitor competes for the active site; excess substrate can overcome it). Non-competitive inhibitors decrease Vmax without changing Km (the inhibitor binds an allosteric site regardless of substrate). Uncompetitive inhibitors decrease both Km and Vmax (binds only the enzyme-substrate complex).