5.1—Overall reaction of photosynthesis

Photosynthesis converts light energy into chemical energy. Light energy splits strong bonds in water, the released hydrogen is combined with carbon dioxide to form glucose, and oxygen is released to the atmosphere.

Glucose stores chemical energy in its bonds and can fuel respiration or be converted into other biological molecules. Water supplies hydrogen and oxygen; carbon dioxide supplies carbon, so the overall process is more than “plants take in carbon dioxide”.

A leaf in light can use the products of water splitting and carbon dioxide fixation to build glucose; the oxygen released is a waste product of the photosynthetic pathway, not the source of glucose carbon.

The overall reaction summarises coupled stages and does not mean every step happens directly in sunlight. Light-dependent and light-independent reactions use different inputs and locations.