Which of the following best explains why an enzyme hasn't evolved to catalyze the following reaction as the first step of glycolysis?
Glucose + P_i -> glucose-6-phosphate
(I) The use of ATP is required for this step to serve as a regulatory control point.
(II) The use of ATP is important because it helps keep its concentration low.Otherwise the high [ATP] would slow glycolysis too much through feedback inhibition.
(III) The large positive $\Delta$ G˚' of this reaction would need to be overcome by an exceedingly high [P_i].
(IV) Inorganic phosphate cannot be specifically placed on the carbon in the 6^th position.

Question

Which of the following best explains why an enzyme hasn't evolved to catalyze the following reaction as the first step of glycolysis?
Glucose + P_i -> glucose-6-phosphate
(I) The use of ATP is required for this step to serve as a regulatory control point.
(II) The use of ATP is important because it helps keep its concentration low.Otherwise the high [ATP] would slow glycolysis too much through feedback inhibition.
(III) The large positive

\Delta

G˚' of this reaction would need to be overcome by an exceedingly high [P_i].
(IV) Inorganic phosphate cannot be specifically placed on the carbon in the 6^th position.

Quizplus · Accepted Answer

The use of ATP is important to keep its concentration low and prevent feedback inhibition, but it is not the main reason why an enzyme hasn't evolved for this reaction. Inorganic phosphate can be specifically placed on the carbon in the 6th position, so option IV is incorrect. The answer is III because the large positive ΔG°' of the reaction would need to be overcome by an exceedingly high concentration of P_i. Option I is incorrect because the use of ATP as a regulatory control is for the second step of glycolysis, not the first.

Which of the Following Best Explains Why an Enzyme Hasn't Δ\DeltaΔ

Which of the Following Best Explains Why an Enzyme Hasn't $\Delta$