What characterizes an endergonic reaction?

• A. It releases free energy
• B. It occurs spontaneously
• C. It requires an input of energy
• D. It is characterized by a negative ΔG

Answer: (C)

An endergonic reaction is characterized by a requirement for an input of energy to proceed. In these reactions, the products have a higher free energy than the reactants, which means that energy must be absorbed from the surroundings for the reaction to take place. This is contrary to exergonic reactions, which release energy.

The distinction of having a positive ΔG (Gibbs free energy change) is also key to understanding endergonic reactions. Because they cannot happen spontaneously without the addition of energy, this is reflected in their positive ΔG values.

Thus, the primary feature that defines an endergonic reaction is the need for energy input, differentiating it from processes that release energy or occur spontaneously without external energy.