5. Both water and glucose share an–OH that can serve as a substrate for a reaction with the terminal phosphate of ATP catalyzed by hexokinase. Glucose, however, is about a million times more reactive as a substrate than water. The best explanation is that:
(A) the larger glucose binds better to the enzyme; it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis.
(B) glucose has more –OH groups per molecule than does water.
(C) the–OH group of water is attached to an inhibitory H atom, while the glucose –OH group is attached to C.
(D) water and the second substrate, ATP, compete for the active site resulting in a competitive inhibition of the enzyme.
(E) water normally will not reach the active site because it is hydrophobic.
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