Question

Which one of the equation pairs illustrates a favorable energetic coupling in a cell? (i.e. One reaction releases sufficient energy to drive the other to completion). Select ALL that apply. Equation 1: ATP + H2O + ADP + Pi AG1 = -7 kcal/mol Equation 2: phosphoenolpyruvate + H2O → pyruvate + Pi AG2 = -14.8 kcal/mol Equation 3: glucose + Pi — glucose-6-phosphate + H2O AG3 = +3.3 kcal/mol Equation 4: ADP + Pi + ATP + H2O AG3 = +7 kcal/mol

Answer 1

Equation 1 and 4 are coupling reactions of a cell . As we all knows that by the process of hydrolysis a considerable amount of energy released. The hydrolysis of ATP to ADP in the following reaction:

ATP + H₂O                ADP + Pi (∆G= -7kcal/mol)

The coupled reactions are depends upon each other in term of energy consumption and production because energy produced by one reaction drive the second reaction and the ΔG of both reaction are sum of the ΔG values of one reactions. Both reactions can take place if the ΔG is negative. Coupling of reactions involves ATP and the shared intermediate which is often a phosphorylated molecule (Pi).

ADP + Pi             ATP + H₂O (∆G= +7kcal/mol)

Hence, the equation pairs for favorable energetic coupling of a cell are Equation 1 and 4