What purpose does the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase serve as the first step in glycolysis?
(a) It helps drive the uptake of glucose from outside the cell.
(b) It generates a high-energy phosphate bond.
(c) It converts ATP to a more useful form.
(d) It enables the glucose 6-phosphate to be recognized by phosphofructokinase, the next enzyme in the glycolytic pathway.
Choice (a) is correct. Choice (b) is incorrect because the phosphate transferred to the glucose is not held by a high-energy covalent bond. Choice (c) is incorrect because the reaction converts ATP to ADP, which is not useful as an energy source for most cellular reactions, even though it still has one high-energy bond. Choice (d) is incorrect because the next enzyme in the pathway is phosphoglucose isomerase, not phosphofructokinase.
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