A mutation in the gene coding for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a nonpolar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has much lower activity than the normal enzyme does. Which of the following most likely explains how the amino acid substitution has resulted in decreased catalytic activity by the mutated enzyme? A The substitution decreased the mass of the enzyme so that the mutated enzyme binds more weakly to the substrate than the normal enzyme does.
B The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does.
C The substitution caused many copies of the mutated enzyme to cluster together and compete for substrate to bind.
D The substitution caused the directionality of the enzyme to change such that the amino terminus of the normal enzyme has become the carboxy terminus of the mutated enzyme.