Which action must occur for an enzyme to catalyze a chemical reaction? a. a noncompetitive inhibitor must first bind to an active site. b. a competitive inhibitor must first bind to an active site. c. a substrate must bind to an allosteric site of the enzyme. d. a substrate must bind to an active site of the enzyme.

For an enzyme to catalyze a chemical reaction it is very essential for the correct substrate to bind to the active site of the enzyme.The active site is divided into two portions : Binding site Catalytic site The binding site is made up of amino acid residues that are responsible for binding to the correct substrate while the catalytic site possesses the amino acids that lead to the catalysis. The shape of the active site is such that only the correct substrate binds to it easily and hence, the catalytic reaction takes place.

The answer is energy. the arrows are showing how exited and energized the stones are.