Which equation models enzyme kinetics with Vmax and Km?

• A. Arrhenius equation
• B. Nernst equation
• C. Bernoulli equation
• D. Michaelis-Menten equation

Answer: (D)

Enzyme kinetics often shows that reaction rate rises with substrate concentration but levels off as enzymes become saturated. The equation that captures this behavior with two defining parameters, Vmax and Km, is the Michaelis-Menten equation: v = (Vmax [S])/(Km + [S]). Vmax is the fastest possible rate when all enzyme active sites are occupied. Km is the substrate concentration at which the rate is half of Vmax, reflecting how readily the enzyme binds substrate—the lower the Km, the higher the affinity. This equation also reveals two useful limits: when [S] is much smaller than Km, v ≈ (Vmax/Km)[S], so the rate increases linearly with [S]. When [S] is much larger than Km, v ≈ Vmax, meaning the enzyme operates at its maximum capacity regardless of further increases in [S]. The other formulas describe different phenomena (temperature dependence, electrochemical potential, fluid dynamics) and do not model enzyme-catalyzed reactions with Vmax and Km.