Why is photosynthesis considered an endergonic reaction?

Photosynthesis is considered an endergonic reaction primarily because it absorbs energy from sunlight to drive the process. During photosynthesis, plants take in carbon dioxide and water, and through a series of chemical reactions that require energy input, specifically from sunlight, they convert these raw materials into glucose and oxygen. The energy from sunlight is captured by chlorophyll in the chloroplasts and is essential for the reactions to occur.

This energy requirement means that the overall reaction is not spontaneous; rather, it requires a continuous input of energy to proceed. In addition, the products of photosynthesis have higher energy content than the reactants, demonstrating that energy has been absorbed, in alignment with the characteristics of endergonic reactions. In this context, the photosynthesis process exemplifies how energy transformation is necessary for creating the complex organic molecules that sustain life in plants and, subsequently, in other organisms that rely on them for energy.