During photosynthesis, what substance is produced as a byproduct?

During the process of photosynthesis, green plants, algae, and some bacteria convert light energy into chemical energy, primarily using carbon dioxide and water. The key stages of photosynthesis occur in the chloroplasts of plant cells where sunlight is captured by chlorophyll.

In the light-dependent reactions, water is split, releasing oxygen as a byproduct. This oxygen is not utilized by the plant itself but is expelled into the atmosphere. It is significant because this oxygen is vital for the survival of aerobic organisms, including humans.

In addition to oxygen, glucose is synthesized during the light-independent reactions (Calvin Cycle). This glucose serves as an energy source for the plant and is utilized in various metabolic processes. However, glucose is the primary product of photosynthesis rather than a byproduct.

Carbon dioxide is a raw material consumed during the photosynthesis process, while water is also a reactant essential for the formation of glucose and the release of oxygen. Thus, oxygen is the only substance that is produced as a byproduct during photosynthesis—specifically, it is the result of water being oxidized in the presence of light energy.