<Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> P700, or photosystem I primary donor, (where P stands for pigment) is the reaction - center chlorophyll a molecule in association with photosystem I. Its absorption spectrum peaks at 700 nm . When photosystem I absorbs light, an electron is excited to a higher energy level in the P700 chlorophyll . The resulting P700 with excited electron is designated P700 *, and is the strongest biological reducing agent (in contrast to P680 of photosystem II, the strongest biological oxidizing agent). The electron is subsequently captured by the primary electron acceptor . Type I photosystems use ferredoxin - like iron - sulfur cluster proteins as terminal electron acceptors . Photosystem I is more complex than photosystem II (P680), as it has a more complex antenna system, has more subunits in its overall structure, and may exhibit cyclic or non-cyclic electron transfer from the excited P700 * to the electron acceptor . </P> <Table> <Tr> <Td> </Td> <Td> This article about an organic compound is a stub . You can help Wikipedia by expanding it . <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> </Table>

What is the difference between p680 and p700
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