Which statement characterizes exergonic reactions?

• A. DeltaG positive
• B. DeltaG negative
• C. They require energy input
• D. They are always anabolic

Answer: (B)

Exergonic reactions release free energy, which is shown by a negative change in Gibbs free energy (ΔG < 0). When ΔG is negative, the products are at a lower free energy than the reactants, so the reaction can proceed spontaneously under constant temperature and pressure. This energy release is what can drive other processes in the cell, such as powering endergonic steps or mechanical work. For example, cellular respiration breaks down glucose and releases energy that the cell captures to make ATP.

In contrast, a positive ΔG means the reaction requires energy input (endergonic), so it wouldn’t be exergonic. Exergonic reactions also aren’t restricted to being anabolic; many are catabolic, breaking down molecules and releasing energy. Activation energy may affect how quickly the reaction occurs, but it doesn’t change the sign of ΔG.