8. An enzyme has the ability to catalyze reactions of several unrelated compounds. The mechanism of how this enzyme operates is best explained byOa. the lock-and-key theoryOb. the induced-fit theoryOc. the enzyme-substrate complexOd. the efficiency of the enzyme

The enzyme catalyzed reaction is the reaction in which biocatalyst known as enzyme binds to the transition state of the reaction and reduces activation energy barrier of the reaction and thereby increasing rate of reaction.Option b is correct because induced fit indicates a continuous change in the conformation and shape of an enzyme is response to the binding of substrate which means when a substrate binds to an enzyme, it will change the conformation of the enzyme. This forms transitional intermediate which lowers the activation energy barrier and increases rate of reaction. Thus, the enzyme will change its configuration until it is complementary to substrate to activate the Enzyme-substrate complex which means the enzyme can catalyze reactions of several unrelated compound as the shape of active site of enzyme is not fixed and changes to complement the shape of substrate upon binding. Option a is incorrect in Lock and Key model, the active site of enzyme is considered to be fixed even before binding which limits the flexibility of enzyme to catalyze reactions of unrelated compounds. Option c is incorrect because the enzyme-substrate complex is formed after binding of substrate of enzyme and can not explain binding of different unrelated compounds. Option d is incorrect because efficiency of an enzyme is the rate at which enzyme is catalyzing the reaction to form products and do not explain binding of enzyme to several unrelated compounds.Hence, option b is correct because enzyme catalyzing reactions of several unrelated compounds can be best explained by Induced-fit theory.