Photosynthesis provides the chemical energy needed to produce these compounds. Certain bacteria and algae can also capture light energy and use it to make food. For example, photosynthetic bacteria contain chlorophyll in tiny bodies called chromatophores. In chromatophores, compounds other than water are combined with carbon dioxide to form sugar. No oxygen is released.
Green plants convert carbon dioxide and water into food and oxygen.
This process, which is called respiration, is the reverse of photosynthesis. Oxygen is used up and carbon dioxide and water are given off. Plants then use the carbon dioxide and water to produce more food and oxygen. The cycle of photosynthesis and respiration maintains the earth's natural balance of carbon dioxide and oxygen. How to cite this article.