Question

What is competitive inhibition? Compare it with allosteric inhibition.

Answer 1

Enzymes are chemical substances that are used to catalyze the reactions inside the bodies. Moreover, enzymes have three kinds of reactions namely, competitive inhibition reaction, non-competitive inhibition reaction, and allosteric reaction.

Complete answer: Competitive Inhibition: Whenever a particular amount of enzyme is reacting with a particular amount of substrate with similar active sites, keeping the temperature of the reaction constant, then gradually all the substrate is fully consumed. The reaction between the enzyme and substrate here is like a lock and key. Now if in this same reaction, the temperature is kept constant, and then a molecule of another competitive inhibitor is added, that has the same active site like substrate, then the competitive inhibitor binds with the molecules of the enzymes. The inhibitor does not let the substrate-enzyme reaction to occur. Hence, the inhibitor competes with the substrate for the active sites of the enzyme and binds with them to stop the effect produced by the substrate-enzyme reaction. This mechanism is known as competitive inhibition, where we inhibit the effect of an enzyme by blocking its active site by inhibitors.
Allosteric Inhibition: If in a chemical reaction, the product formed is in high concentration, and this concentration either stimulates or blocks the activity of enzymes by which it is formed, then it is known as allosteric inhibition. Hence, in allosteric inhibition, the stimulation or inhibition is carried out due to the action of the own enzyme.
Thus, as compared with allosteric inhibition, competitive inhibition requires external inhibitors for competing with the substrate for the active site of the enzyme whereas, in allosteric inhibition, the enzyme inhibits itself-reaction.

Note: An enzyme molecule has various kinds of sites present on its surface. These sites are used for attachment with the substrate. The active sites are those sites of a molecule where these substrate reactions occur. These active sites are found at the point of the folding of proteins.