Question

Which of these equations demonstrates energetic coupling in a cell? equation 1: atp + h2o → adp + pi δg1 = –7 kcal/mol equation 2: phosphoenolpyruvate + h2o → pyruvate + pi δg2 = –14.8 kcal/mol equation 3: glucose + pi → glucose-6-phosphate + h2o δg3 = +3.3 kcal/mol equation 4: adp + pi → atp + h2o δg3 = +7 kcal/mol?

Answer 1

I believe the most appropriate equations are 1 and 3; that is
ATP + H2O = ADP + Pi ΔGI =- 7 kcal/mol and
Glucose + Pi = Glucose-6-phosphate +H2O ΔG3 = +3.3 kcal/mol
Reaction coupling is a strategy used by cells in which an energetically favorable reaction such as hydrolysis of ATP is directly linked with an energetically unfavorable reaction.