EMCC Biology Test 2 Practice 2026 - Free Biology Practice Questions and Study Guide

Photosynthesis is classified as an endergonic reaction. This classification is important because endergonic reactions are characterized by the consumption of energy to drive the process forward, resulting in the formation of higher-energy products from lower-energy reactants. In the case of photosynthesis, plants take in carbon dioxide and water, and using sunlight as an energy source, they convert these reactants into glucose and oxygen. The energy captured from light is stored in the chemical bonds of glucose, making the overall reaction one that requires input energy, hence it is endergonic.

In contrast, exothermic reactions release energy, exergonic reactions release free energy, and catabolic reactions typically refer to the breakdown of larger molecules into smaller ones, which is not the case in photosynthesis since it involves the synthesis of glucose.