Which term describes a reaction that absorbs free energy from its surroundings?

• A. Endergonic reaction
• B. Exergonic reaction
• C. Catabolic reaction
• D. Anabolic reaction

Answer: (A)

Reactions that absorb free energy from their surroundings require energy input to proceed. This kind of reaction is called endergonic. It has a positive ΔG, so it isn’t spontaneous on its own and needs an energy source—cells often supply that energy by coupling to ATP hydrolysis or other exergonic steps. In biology, endergonic processes power building things up, like synthesizing glucose or proteins, which is why anabolic pathways are typically endergonic. Exergonic reactions, by contrast, release energy and can occur spontaneously (negative ΔG). So the term describing a reaction that absorbs free energy from its surroundings is endergonic.