Question

the enzyme hexokinase catalyzes the conversion of glucose to glucose - 6 - phosphate, which is an important step in glycolysis. the reaction involves the transfer of a phosphate group from atp to glucose. either a glucose molecule or a water molecule can fit in the active site of hexokinase. the presence of a water molecule in hexokinases active site would result in the hydrolysis of atp to adp instead of the conversion of glucose to glucose - 6 - phosphate. which of the following statements best helps explain the reaction specificity of hexokinase? a both glucose and water are polar molecules that form favorable interactions with charged and polar amino acid side chains in hexokinases active site. b both glucose and water have oxygen atoms that can form covalent bonds with the phosphorus atoms of phosphate groups. c glucose is an energy - rich organic molecule that can be broken down by glycolysis to produce atp, whereas water is an inorganic molecule. d glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

Explanation:

Hexokinase's reaction specificity relies on the induced fit model: only glucose triggers the structural change in hexokinase’s active site required for catalyzing glucose phosphorylation. Water, though fitting the active site, does not induce this change, so ATP hydrolysis (instead of glucose phosphorylation) occurs when water is present. This explains why hexokinase primarily catalyzes glucose to glucose-6-phosphate (the glycolysis step) rather than ATP hydrolysis by water.

Answer:

D. Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.