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Keyword - Photosystem I (KW-0603)

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Protein involved in photosystem I (PSI), a complex that uses light energy to mediate electron flow in the chloroplast thylakoid membrane of plants and in cyanobacteria. In linear electron flow, PSII is coupled to PSI and produces a pH gradient, ATP and NADPH. In cyclic electron flow, PSI generates a pH gradient and ATP. PSI is excited best by light at about 700 nm, and is thus sometimes called P700. PSI is an iron-sulfur type reaction center (RC), sharing a common ancestor with the RCs of Heliobacteriaceae, green sulfur and green non-sulfur bacteria.


  • P700
  • PSI


Cellular component

Gene Ontology


photosystem I [ GO:0009522 ]


PhotosynthesisPhotosystem ICellular componentBiological process
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