Question

Could someone explain why this is wrong?

Which of the following concerning allosteric inhibitors is NOT true?
a) can inhibit an enzyme by changing the shape of the active site
b) can inhibit an enzyme by changing the shape of the enzyme
c) can inhibit an enzyme by covering the active site
d) all of these are not true

The answer was d, but I don't understand why. I put b because it only changes the shape of the active site and not the enzyme itself, but that was wrong.

Answer 1

The answer is; C

An allosteric protein does not bind to the active site of an enzyme. Only the subtrate binds the active site. However, some enzymes have an allosteric site where the allosteric protein binds and influences the conformation of the enzyme. This change in conformation on binding may facilitate or inhibit the binding of subtrate to the enzyme active site. Therefore, there are two type of allosters; inhibitors and activators.

Answer 2

Correct answer: d) All of these are not true

An allosteric inhibitor binds to an enzyme, it is a negative control of an enzyme that is attached to an inhibitory substance. Due to this binding, there is a slight change in the active site of the enzyme that makes them work less efficiently.

This binding leads to a conformational change that reduces the affinity of binding of substrate to the enzyme.

Hence, the correct answer would be option D.