Editing Photosystem I (section)

=== P700 reaction center ===
{{main article|P700}}
The P700 reaction center is composed of modified [[Chlorophyll a|chlorophyll ''a'']] that best absorbs light at a wavelength of 700&nbsp;[[Nanometre|nm]].<ref name="rutherford">{{cite journal | vauthors = Rutherford AW, Heathcote P | title = Primary photochemistry in photosystem-I | journal = Photosynthesis Research | volume = 6 | issue = 4 | pages = 295–316 | date = December 1985 | pmid = 24442951 | doi = 10.1007/BF00054105 | bibcode = 1985PhoRe...6..295R | s2cid = 21845584 }}</ref> P700 receives energy from antenna molecules and uses the energy from each photon to raise an electron to a higher energy level (P700*). These electrons are moved in pairs in an [[redox|oxidation/reduction]] process from P700* to electron acceptors, leaving behind P700{{sup|+}}. The pair of P700* - P700{{sup|+}} has an [[electric potential]] of about −1.2 [[volt]]s. The reaction center is made of two chlorophyll molecules and is therefore referred to as a [[Dimer (chemistry)|dimer]].<ref name="Taiz"/> The dimer is thought to be composed of one chlorophyll ''a'' molecule and one chlorophyll ''a''′ molecule. However, if P700 forms a complex with other antenna molecules, it can no longer be a dimer.<ref name="Shubin"/>