P680 - Citizendia

P680, or Photosystem II, (where P stands for photosystem) is the reaction-center associated with photosystem II and consists of 2 chlorophyll a molecules that are not bound to proteins unlike the other chlorophyll molecules in photosystem II. A photosynthetic reaction center is a complex of three types of protein that is the site where molecular excitations originating from sunlight are transformed into a series of electron-transfer Photosystem II is the first protein complex in Light Dependent Photosynthesis. Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria. Its absorption spectrum peaks at 680 nm, which is in the red part of the spectrum. A material's absorption spectrum shows the fraction of incident Electromagnetic radiation absorbed by the material over a range of Frequencies. When photosystem II absorbs light, an electron is excited to a higher energy level. A quantum mechanical system or particle that is bound, confined spacially can only take on certain discrete values of energy as opposed to classical particles which This electron drops down to its ground state level and releases energy, which is then transmitted through a light-harvesting complex (LHCII) until it reaches a P680 chlorophyll and excites an electron on the P680 molecule. A light-harvesting complex is one or more Polypeptide chains containing photosynthetic Pigments which surrounds a photosynthetic Reaction centre The resulting P680 with excited electron is designated P680*. The electron is subsequently captured by the primary electron acceptor. To replace the electron water will be oxidized in the Oxygen evolving complex. The oxygen evolving complex, (OEC also known as the water-splitting complex is a water oxidizing enzyme involved in the photooxidation of water during the Light reactions

P680 is the strongest biological oxidizing agent known.

See also