The fact that an enzyme-catalyzed reaction is first order with respect to substrate at low substrate concentration but becomes zero order with respect to substrate at high substrate concentration is explained by
A) the catalytic constant.
B) reversibility of formation of the enzyme-substrate complex.
C) three point attachment.
D) specificity.
E) saturation.

Question

Quizplus · Accepted Answer

This phenomenon is explained by the concept of saturation. At low substrate concentrations, the rate of the enzyme-catalyzed reaction increases linearly with substrate concentration, indicating first-order kinetics. However, at high substrate concentrations, the enzyme becomes saturated with substrate, meaning all active sites are occupied, and the reaction rate reaches a maximum and becomes independent of substrate concentration, indicating zero-order kinetics.

The Fact That an Enzyme-Catalyzed Reaction Is First Order with Respect