Question

multiple choice question

for an apoenzyme to become a functional holoenzyme, it must ______.

bind to a substrate
bind to a cofactor
drop in temperature
rise in temperature

Explanation:

Define apoenzyme and holoenzyme

An apoenzyme is the inactive, protein portion of a conjugated enzyme that requires an organic or inorganic cofactor to become catalytically active. A holoenzyme is the complete, active enzyme system consisting of the apoenzyme combined with its cofactor.

Identify the activation requirement

To transition from an inactive apoenzyme to a functional holoenzyme, the apoenzyme must physically bind to its specific cofactor (or coenzyme).

Evaluate the given options

• "bind to a substrate": Substrate binding occurs after the active holoenzyme is formed.
• "bind to a cofactor": This directly completes the active holoenzyme structure.
• "drop in temperature" / "rise in temperature": Temperature changes affect reaction rates or enzyme stability but do not chemically convert an apoenzyme into a holoenzyme.

Answer:

• bind to a substrate
• bind to a cofactor (Correct answer)
• drop in temperature
• rise in temperature