Where does the oxygen released from photosynthesis come from?

The oxygen released during photosynthesis primarily comes from the water that plants use in the process. During photosynthesis, chlorophyll in plant cells captures sunlight and utilizes it to convert carbon dioxide from the air and water absorbed by the roots into glucose and oxygen. The water molecule is split in a reaction known as photolysis, which occurs in the light-dependent reactions of photosynthesis. This splitting of water (H2O) releases oxygen (O2) as a byproduct.

Furthermore, the carbon dioxide and glucose molecules do not contribute to the oxygen released in the same way. While carbon dioxide is an essential reactant in the overall photosynthesis process, it is not the source of the oxygen. The glucose produced is an energy storage molecule and also does not release oxygen. The oxygen in the air is a result of numerous photosynthetic organisms and is not directly related to the process occurring within individual plants at that moment. Thus, it is the water that directly provides the oxygen produced during photosynthesis.