Light and water Essay

When light and water are absorbed by the plant, four light photons are assigned to Photosystem II while the energy is channeled to P680. This energy triggers the P680 molecule to release four electrons toward an electron acceptor in the thylakoid membrane. To fill up the â€Å"hole† in the P680 molecule, it will strongly attract two water molecules and break it up. Two atoms of Oxygen are released and form the gas that humans need while 4 atoms of hydrogen are taken for photosynthesis. The four hydrogen atoms become energized and are passed on to the next P680. This process will then continue to happen to a series of other protein carriers creating what is called an electron transport chain. This transferring of electrons makes the energy of these electrons fall to a lower level resulting to the release of energy. The energy can be classified as metabolic (ATP) or reducing (NADPH). These and carbon dioxide are used in the carbon fixation process or â€Å"Calvin Cycle. † Because the next steps do not need light, it is called the light-independent reactions. The Calvin Cycle is called such because its end-products (molecules of RuBP) are needed to keep the process going. Firstly, carbon dioxide and five carbon molecules called ribulose 1. 5 biphosphate (RuBP) join together so that the organism can use CO2 to synthesize glucose and other complex carbohydrates. This is carbon fixation and it cycles three times to form six three-carbon molecules (3PG) which are chemically restructured to become glyceraldehyde 3-phosphate(G3P) molecules. One of these G3P is needed to make carbohydrates while the rest are used to resynthesize three molecules of RuBP in the next cycle.