Question

What would be the net ΔG' for the coupling of these two reactions?

1) +7.007 kcal/mol
2) +3.459 kcal/mol
3) -1.774 kcal/mol
4) -3.459 kcal/mol
5) -7.007 kcal/mol

Answer 1

The net ΔG' for the coupling of ATP hydrolysis and glucose phosphorylation reactions is -4 kcal/mol, which indicates a spontaneous and exergonic coupled reaction under standard conditions.

Step-by-step explanation:

In determining the net Gibbs free energy change (ΔG') for the coupling of two biochemical reactions, we take into account the individual ΔG' values for each reaction. We are given that the ATP hydrolysis releases approximately 7 kcal/mol and is thus exergonic. On the other hand, the glucose phosphorylation reaction requires an input of energy, exhibiting a ΔG' of +3 kcal/mol which makes it endergonic.

When coupling these reactions, the overall ΔG' is calculated by summing the individual values: -7 kcal/mol (from ATP hydrolysis) and +3 kcal/mol (from glucose phosphorylation) giving us a net ΔG' of -4 kcal/mol for the coupled reaction. This net energy change indicates that the coupled process can occur spontaneously under standard conditions in a closed system because it is exergonic, with the energy released by ATP hydrolysis driving the energetically unfavorable glucose phosphorylation.