Consider the following two chemical equations:
A. glucose + fructose → sucrose + H₂O, Δ G = +27 kJ/mole (or +6.5 kcal/mole)
B. glucose + fructose + ATP → sucrose + ADP + P_i, Δ G = −5 kJ/mole (or −1.2 kcal/mole)
The overall free energy change in the chemical equations (A) and (B) above is accomplished by

A) a decrease in activation energy.
B) combining two endergonic reactions.
C) combining an endergonic and an exergonic reaction.
D) combining two exergonic reactions.
E) measuring the reaction rate.

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Dania Nieto · Accepted Answer

Final Answer : C, Explanation :  Equation A is endergonic (requires energy, ΔG is positive), and equation B is exergonic (releases energy, ΔG is negative). Combining these reactions, where ATP hydrolysis drives the formation of sucrose, illustrates combining an endergonic and an exergonic reaction.

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