P700

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P700 is the reaction-center chlorophyll a molecule associated 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*. The electron is subsequently captured by the primary electron acceptor. Type I photosystems use ferredoxin-like iron-sulfur cluster proteins as terminal electron acceptors.