Some organisms produce their own food using light energy in a process called photosynthesis. Plants, algae, some protists, and some bacteria carry out photosynthesis. Photosynthesis relies on pigments, the most common of which is chlorophyll; chlorophyll gives plants their green color.
Photosynthesis uses light energy to make sugars, which can be used later for fuel.
One of the important waste products of photosynthesis is oxygen gas. Where does this oxygen gas come from?
Oxygen is released when water is broken down to extract electrons and protons for use in the light reactions.