Phosphorylation of glucose to glucose-6-phosphate is:

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Multiple Choice

Phosphorylation of glucose to glucose-6-phosphate is:

The key idea here is energy input. Phosphorylating glucose to glucose-6-phosphate has a positive standard free-energy change (+13.8 kJ/mol) when viewed as the phosphorylation step by itself. A positive ΔG means the reaction is not spontaneous under standard conditions and would require an input of energy to proceed. In cells this step is driven by coupling to ATP hydrolysis, which releases a large amount of energy (roughly -30 kJ/mol). When you pair the glucose phosphorylation with ATP breakdown, the overall ΔG becomes negative, so the process can proceed. That’s why the phosphorylation step itself is best described as endergonic, not exergonic, not at equilibrium, and not spontaneous at all temperatures.

The key idea here is energy input. Phosphorylating glucose to glucose-6-phosphate has a positive standard free-energy change (+13.8 kJ/mol) when viewed as the phosphorylation step by itself. A positive ΔG means the reaction is not spontaneous under standard conditions and would require an input of energy to proceed. In cells this step is driven by coupling to ATP hydrolysis, which releases a large amount of energy (roughly -30 kJ/mol). When you pair the glucose phosphorylation with ATP breakdown, the overall ΔG becomes negative, so the process can proceed. That’s why the phosphorylation step itself is best described as endergonic, not exergonic, not at equilibrium, and not spontaneous at all temperatures.

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