Photosynthesis Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting
Fractionation of carbon isotopes in oxygenic photosynthesis + 2 H + 3 ATP + OThe light-independent reactions undergo the Calvin-Benson cycle, in which the energy from NADPH and ATP is used to convert carbon dioxide and water into organic compounds via the enzyme RuBisCO. The overall general equation for the light-independent reactions is the following:3 CO + 9 ATP + 6 NADPH + 6 H → CHO-phosphate + 9 ADP + 8 P + 6 NADP + 3 HOThe 3-carbon products (CHO-phosphate) of the Calvin cycle are later converted to glucose or other carbohydrates such as starch, sucrose, and cellulose. The large fractionation of C in photosynthesis