In the first reaction of the glycolytic pathway, the enzyme hexokinase uses ATP to catalyze the phosphorylation of glucose, yielding glucose 6-phosphate and ADP. The ΔG° value for this reaction is -17 kJ/mole. The enzyme glucose 6-phosphatase catalyzes a "reverse" reaction, in which glucose 6-phosphate is converted back to glucose, and a phosphate is released. The ΔG° value for this reaction is -14 kJ/mole. What is the ΔG° value for the following reaction? ATP + H₂O → ADP + Pᵢ

Question

Quizplus · Accepted Answer

The two reactions described in the question can be written as:
ATP + glucose → ADP + glucose 6-phosphate ΔG°= -17 kJ/mole
glucose 6-phosphate + H₂O → glucose + Pᵢ ΔG°= -14 kJ/mole
Combining these reactions yields the ATP hydrolysis reaction presented in the question. Since the free-energy changes are additive, the ΔG° value for this combined reaction is the sum of the ΔG° values for the two reactions above:
(-17 kJ/mol) + (-14 kJ/mole) = -31 kJ/mole.

In the First Reaction of the Glycolytic Pathway, the Enzyme