Final answer:
An endergonic reaction is a chemical reaction for which ΔG is positive and requires an input of energy. The products have more free energy than the reactants, making them energy-storing molecules. These reactions do not occur spontaneously and require the addition of free energy.
Step-by-step explanation:
An endergonic reaction is best described as a chemical reaction for which the change in Gibbs free energy (ΔG) is positive. This means that the reaction requires an input of energy rather than releasing energy. In endergonic reactions, the products have more free energy than the reactants, making them energy-storing molecules. These reactions are non-spontaneous and will not occur on their own without the addition of free energy.