Rank these reactions from least to most energetically favorable. 1. glucose to glucose-6-p, +3.3kcal/mol

2. pep to pyruvate, -14.8kcal/mol

3. atp to adp and pi, -7.3kcal/mol

4. glucose-6-p to fructose-6-p, +0.4kcal/mol

The correct answer is "1. Glucose to Glucose-6-P, +3.3kcal/mol, 4. Glucose-6-P to Fructose-6-P, +0.4kcal/mol, 3. ATP to ADP and Pi, -7.3kcal/mol, 2. PEP to pyruvate, -14.8kcal/mol".

Explanation:

In chemistry, a reaction is more energetically favorable if less energy input is needed to make it happen. A common term used to describe if a reaction is favorable or not is the Gibbs free energy (ΔG), which describes the change of free energy in the reaction. If ΔG is positive, the reaction is not spontaneous and therefore is not energetically favorable, whereas if ΔG is negative it is energetically favorable. The energy in kcal/mol of the reactions given in the question is closely related to ΔG. Therefore, the more positive is the kcal/mol value the less energetically favorable the reaction is. This ranks the reactions as follows: 1. Glucose to Glucose-6-P, +3.3kcal/mol, 4. Glucose-6-P to Fructose-6-P, +0.4kcal/mol, 3. ATP to ADP and Pi, -7.3kcal/mol, 2. PEP to pyruvate, -14.8kcal/mol.