Question

The reaction converting glycerol to glycerol-3-phosphate is energetically unfavorable by 9.2 kJ. The reaction of ATP with water to yield ADP, hydrogen phosphate ion, and hydrogen ion is energetically favorable by 30.5 kJ. These reactions are coupled so that the overall process is energetically favorable. What is ΔG for the overall process?

Answer 1

Answer:

ΔG for overall reaction :  -21.3 kJ

Explanation:

Reaction of the conversion of glycerol to glycerol-3-phosphate is unfavorable and thus is coupled with second reaction that involves the conversion of ATP to ADP which is highly energetically favorable.

Reaction 1:  Glycerol + HPO₄²⁻ ⇒ Glycerol-3-phosphate + water

Reaction 2:             ATP  + H₂O ⇒ ADP + HPO₄²⁻ + H⁺

ΔG for reaction 1 : 9.2 kJ (non-spontaneous : Positive value)

ΔG for reaction 2 : -30.5 kJ (spontaneous : Negative value)

The overall coupled reaction is:

Glycerol + ATP ⇒ Glycerol-3-phosphate + ADP + H⁺

ΔG for overall reaction : 9.2 kJ + (-30.5 kJ) = -21.3 kJ

negative sign signifies that the overall reaction is spontaneous.