photosynthesis Photosynthesis is a biochemical process in which plants, algae, and some bacteria harness the energy of light to produce simple nutrient molecules, such as glucose. During photosynthesis, simple sugars are produced by combining carbon dioxide and water using light (sunlight) as an energy source and producing oxygen as a by-product. Notice that some forms of photosynthesis do not release oxygen. The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide (CO2) using energy obtained from light rather than from the oxidation of chemical compounds. [source: GO] The carboxylation process is generally known as CO2 fixation (carbon fixation), and the oxygenation process is known as photorespiration. pathway GO:0015979 UPa:UPA00091 energy metabolism