A biologist working in a lab adds a compound to a solution t

A biologist working in a lab adds a compound to a solution that contains an enzyme and its substrate. This compound binds to the enzyme and decreases the rate at which the enzyme converts substrate to product. This decrease cannot be overcome by increasing the concentration of substrate to the reaction mix. Therefore, which of the following is TRUE of the compound?

a. The compound is an allosteric activator.

b. The compound is an allosteric inhibitor.

c. The compound is an inhibitor that binds to the active site of the enzyme.

d. The compound is a catalyst for the reaction.

Solution

Correct option- (d) the compound is an inhibitor that binds to the active site of the enzyme

Explanation- Allosteric activator or positive allosteric modulator is binding of compound (ligand),which is product of a chain reaction, to the enzyme. Due to this enzyme substrate attraction increases. Means product formation rate increases. But here rate of formation of the product decreases. So the compound cannot be allosteric activator.

Allosteric inhibitor or negative allosteric modulator is binding of a compound (ligand), which is product of a chain reaction, to the enzyme. Due to this enzyme substrate attraction decreases. Means product formation rate decreases. But in this case rate of product formation decreases after adding the compound. So, the compound cannot be allosteric inhibitor.

Catalyst catalyzes the reaction rate. But in this case product formation rate decreases. So, the compound cannot be catalyst.

Inhibitor is a compound which binds to the active site of the enzyme competitively and decreases the enzyme substrate attraction. Means, product formation rate decreases. In this case, exactly same incident occurred. So the compound is an inhibitor.