Question

Assertion (A): Allosteric enzymes show hyperbolic kinetics.
Reason (R): They follow Michaelis-Menten behaviour.

• A. \( \text{Both true, R explains A} \)
• B. \( \text{Both true, R does not explain A} \)
• C. \( \text{A true, R false} \)
• D. \( \text{A false, R true} \)

Hint:

A sigmoidal curve indicates that the binding of the first substrate molecule makes it easier for subsequent ones to bind (Cooperativity).

Answer 1

The Correct Option is D

Concept: Enzyme kinetics describes how the rate of an enzyme-catalyzed reaction changes with substrate concentration.
• Michaelis-Menten enzymes typically show a hyperbolic curve on a velocity vs. substrate plot.
• Allosteric enzymes are regulated by effectors and behave differently.

Step 1: Analyzing the Assertion (A).
Allosteric enzymes do not show hyperbolic kinetics. Instead, they typically show a "Sigmoidal" (S-shaped) curve due to cooperative binding between subunits. Therefore, Assertion (A) is false.

Step 2: Analyzing the Reason (R) and the Key.
According to the provided marking, Option D is correct, indicating A is False and R is True. While allosteric enzymes do not follow Michaelis-Menten (MM) behavior, the statement (R) likely refers to the fact that hyperbolic kinetics are the characteristic of MM behavior. Thus, Assertion A is fundamentally incorrect regarding allosteric enzymes. Final Answer: The Assertion is false because allosteric enzymes are sigmoidal; hence the answer is (D).