Question

Which of the following statements is incorrect ?
A.The competitive inhibitor does not affect the rate of breakdown of the enzyme substrate complex.
B.The presence of the competitive inhibitor decreases the km of the enzyme for the substrate.
C.A competitive inhibitor reacts reversibly with the enzyme to form an enzyme- inhibitor complex.
D.In competitive inhibition the inhibitor molecule is not chemically changed by the enzyme.

Answer 1

Hint:Enzymes are biological catalysts that increase the rate of reaction.It consists of active site and regulatory site. Substrate binds to the active site for the reaction to proceed. If the inhibitor binds to an active site then is said to be competitive inhibition and if the inhibitor binds to a regulatory site then it is said to be non competitive inhibition.

Complete step by step answer :
-Competitive inhibition is a type of enzyme inhibition in which the inhibitor binds to the active site on the enzyme.
-This prevents binding of the substrate to the enzyme and hence affects the rate of breakdown of enzyme substrate complex.
-Competitive inhibitors bind reversibly to the active site of the enzyme to form enzyme-inhibitor complexes.
-Due to this maximum velocity is unchanged while km is increased as inhibitor interference with the binding of substrate and this inhibition can be overcome by increasing the substrate concentration.
-In this the inhibitor molecule is not changed chemically by the enzyme .

So the correct option is ( B ).

Additional information:
-With increase in substrate concentration the velocity of the enzymatic reaction rises at first . -The reaction ultimately reaches a maximum velocity which is not exceeded by any further rise in concentration of the substrate this is because there are fewer enzyme molecules than the substrate molecules and there are no free enzyme molecules by the addition of substrate molecules.
-The binding of an enzyme is sensitive to the presence of specific chemicals that binds to enzymes . When the binding of the chemical shut off enzyme activity the process is called inhibition in the chemical is called inhibitor.

Note:
Example of a competitive inhibitor of succinic dehydrogenase by malonate which closely resembles the substrate succinate in structure.
Competitive inhibitors are used in control of bacterial pathogens.