Final answer:
The overall reaction A -> C is energetically favorable because the sum of the individual ΔGs is negative, which indicates that the reaction is spontaneous and will not require an input of energy.
Step-by-step explanation:
The student asked about the enzyme catalyzed reaction pathway A -> B -> C, given that ΔG for A -> B is 5.0 Kcal/mol and ΔG for B -> C is -10.2 Kcal/mol. To determine the overall favorability of the reaction pathway A -> C, we add the individual ΔGs together (5.0 Kcal/mol + (-10.2 Kcal/mol) = -5.2 Kcal/mol). Since the overall ΔG is negative, the reaction from A to C is energetically favorable.
Considering that energetically favorable reactions are those with a negative Gibbs free energy change (ΔG), and that enzymes lower the activation energy for a reaction, we can conclude the overall reaction is spontaneous. Thus, the correct answer to the student's question is that the overall reaction A -> C is energetically favorable, as it does not require an input of energy for C to be produced because the net change in Gibbs free energy (ΔG) for the reaction is negative.