Practice Questions

TLS Online TPP Program

#Question id: 563

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:

#XL - Q Biochemistry

glucose has more —OH groups per molecule than does water.
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.
the —OH group of water is attached to an inhibitory H atom, while the glucose —OH group is attached to C.
water and the second substrate, ATP, compete for the active site resulting in a competitive inhibition of the enzyme.