Microbiology Essay Example | Topics and Well Written Essays - 500 words - 1

Microbiology - Essay Example There are 2 types of photophosphorylation and they are cyclic and noncyclic. In cyclic photophosphorylation, the electron begins in a pigment complex called photosystem I, passes from the primary acceptor to plastoquinone, then to cytochrome b6f (a similar complex to that found in mitochondria), and then to plastocyanin before returning to chlorophyll. In the noncyclic type, first, a water molecule is subjected to photolysis and broken down into 2H+ + 1/2 O2 + 2e- The two electrons released thus from the water molecule are kept in photosystem II. The 2H+ and 1/2O2 are left out for further use. Thereafter, a photon is absorbed by chlorophyll pigments on surrounding the reaction core center of the photosystem. The light excites the electrons of each pigment and this causes a chain reaction. The reaction transfers energy to the core of photosystem II and causes excitation of the two electrons that are transferred to the primary electron acceptor, pheophytin.