NBEO Biochemistry Practice Exam

When Km is high, it indicates that a larger concentration of substrate is required to achieve half of the maximum reaction velocity of the enzyme. This situation reflects a lower affinity between the enzyme and the substrate.

In enzyme kinetics, Km, or the Michaelis constant, represents the substrate concentration at which an enzyme operates at half its maximum velocity (Vmax). A high Km suggests that the enzyme does not bind the substrate efficiently, and therefore, higher concentrations of the substrate are needed for the enzyme to reach its effective binding capability. Consequently, this means the enzyme's affinity for the substrate decreases as Km increases, leading to the conclusion that the enzyme has a low affinity when Km is high. This understanding is crucial in biochemistry, especially in the context of drug development and metabolic regulation, where enzyme-substrate interactions play a vital role in physiological processes.