Glycolysis is the process by which energy is harvested from glucose by living things. Several of the reactions of glycolysis are thermodynamically unfavorable (nonspontaneous), but proceed when they are coupled with other reactions. Reaction A: Pi+glucose⟶glucose-6-phosphate+H2O Δ????=13.8 kJ/mol Reaction B: Pi+fructose-6-phosphate⟶fructose-1,6-bisphosphate+H2O Δ????=16.3 kJ/mol Reaction C: ATP+H2O⟶ADP+Pi Δ????=−30.5 kJ/molWhich is(are) the unfavourable reaction ? (select all that apply)

When talking about bioenergetics, we consider the Gibbs free energy (G), which is the quantity of energy capable of doing the work during a chemical reaction.

When a reaction liberates energy, meaning that system ended up with less free energy, the variation in free energy (ΔG) has a negative sign, and we can say that the reaction is exergonic, or spontaneous, or favorable.

On the other hand, when a reaction gains energy, it means that the system requires that energy to do the work, so the variation in free energy in this case has a positive sign, and we can say that the reaction is endergonic, or nonspontaneous, or unfavorable.

In this statement, the conversion of glucose into glucose-6-phosphate (Reaction A) has a positive variation of free energy (ΔG = 13.8 kJ/mol), so it is unfavorable.

The same case with the conversion of fructose-6-phosphate into fructose-1,6-bisphosphate (Reaction B), with a positive variation of free energy of ΔG = 16.3 kJ/mol, which makes this reaction unfavorable as well.

From this we can say that binding the inorganic phosphate to a molecule requires energy, contrary to the ATP hydrolisis reaction (Reaction C), which is a favorable reaction that liberates that energy by liberating the phosphate (negative variation of free energy ΔG = −30.5 kJ/mol).