P700

P700, or Photosystem I, (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*. The electron is subsequently captured by the primary electron acceptor. Type I photosystems use ferredoxin-like iron-sulfur cluster proteins as terminal electron acceptors.

Components
P700 is a protein complex made of several subunits, that are mainly hydrophobic.