photosystem

A membrane-bound complex in plants and photosynthetic bacteria, responsible for light-harvesting and primary electron transfer. Comprises light-harvesting pigments such as chlorophyll; a primary electron-transfer centre, and secondary electron carriers. In green plant photosynthesis, Photosystem I transfers electrons from plastocyanin to a [2Fe-2S] ferredoxin, and contains iron-sulfur proteins. Photosystem II transfers electrons from the oxygen-evolving complex to plastoquinone, and contains an iron centre.
Source:
PAC, 1997, 69, 1251 (Glossary of terms used in bioinorganic chemistry (IUPAC Recommendations 1997)) on page 1292