Question

The following enzyme reaction is applicable for which order?

(a) Zero order

(b) Zero-First order

(c) Zero-Second order

(d) First order

The question was asked in an international level competition.

My doubt stems from General Reaction Kinetics for Biological Systems topic in section Homogenous Reactions of Bioprocess Engineering

Answer 1

The answer to this question depends on the nature of the enzyme reaction, particularly the concentration of the substrate.

Enzyme-catalyzed reactions typically follow Michaelis-Menten kinetics, which can exhibit different orders under varying conditions:

• Zero-order kinetics: This occurs when the substrate concentration is very high, and the enzyme is saturated, so the reaction rate is constant and independent of substrate concentration.
• First-order kinetics: This occurs when the substrate concentration is very low, and the reaction rate is directly proportional to the substrate concentration.

Given the options, zero-order kinetics is most often applicable when the enzyme is saturated with the substrate, and the reaction rate becomes independent of further increases in substrate concentration.

Thus, the most appropriate answer is:

(a) Zero order.