Do exergonic (-G) reactions release energy and occur spontaneously?

Exergonic reactions are characterized by a negative change in Gibbs free energy (ΔG < 0), which indicates that the energy of the products is lower than that of the reactants. This release of energy is what makes these reactions spontaneous under standard conditions. The term "spontaneous" in this context means that the reaction can occur without external energy input, although the rate at which the reaction occurs can vary; it is not dictated by whether the reaction is exergonic or endergonic.

Therefore, the correct assertion that exergonic reactions release energy aligns with the thermodynamic principle that reactions with a negative ΔG are energetically favorable and can proceed without requiring additional energy. This spontaneity is a fundamental concept in biochemistry, especially in metabolic pathways, where many critical reactions are exergonic, providing energy for cellular processes.