Photosynthetic reaction centre

A photosynthetic reaction centre is a protein that is the site of the light reactions of photosynthesis. The reaction centre contains pigments such as chlorophyll and phaeophytin. These absorb light, promoting an electron to a higher energy level within the pigment. The free energy created is used to reduce an electron acceptor, and is critical for the production of chemical energy during photosynthesis.

Reaction centres are present in all green plants and in many bacteria and algae. Green plants have two reaction centres known as photosystem I and photosystem II and the structures of these centres are complex, involving a multisubunit protein. The reaction centre found in Rhodopseudomonas bacteria is currently better understood since it has fewer proteins than the examples in green plants.