Question

Which statement is TRUE about enzyme inhibition?

A. In competitive inhibition the inhibitor binds to the allosteric site of the enzyme

B. In competitive inhibition the inhibitor binds to the active site of the enzyme

C. In irreversible inhibition, a poison binds to the enzyme so that it can neverwork

D. All above are true

Answer 1

Enzymes are proteins (mostly) that speed up the rate of reaction in the cell. They play an important role in metabolism as biochemical reactions are catalyzed by enzymes (makes the reaction thermodynamically favorable and products are formed). There are many molecules that have effects on enzymatic activity and molecule which inhibits or lower the enzyme activity are known as inhibitors. Some inhibitors bind to the active sites (site at which substrate binds during the enzymatic reactions) whereas others bind to the other site present in the enzyme and affect the enzyme activity.

Option "B" is a true statement about enzyme inhibition. In competitive inhibition, the inhibitor binds to the active site of the enzyme. The inhibitor molecule shares the similarity with the substrate for enzyme and competes for the active site of the enzyme. Binding of the inhibitor to the active site makes enzyme unavailable for the substrate and inhibits the enzyme activity. Competitive inhibition is reversible and when substrate concentration exceeds, it replaces the inhibitor from enzyme active site and binds to it.

In competitive inhibition, the inhibitor binds to the allosteric site of the enzyme is not the correct answer. Allosteric site is the site that is different site present other than the active site in the enzyme. These sites have a regulatory role and effector molecules bind to these sites and regulate the enzyme activity. Therefore, option "A" is not the right answer.

Poison is non-specific inhibitors and inhibits the activity of all enzymes in the same way and may lead to cell death. The binding of poison to the enzyme alters the enzyme three-dimensional structure makes it's non-functional therefore, it can never work. Binding of poison to the enzyme and inhibit its activity is an example of irreversible inhibition but all irreversible inhibitors are not poison.