P700

A special form of *chlorophyll a with an absorption peak for light of 700 nm wavelength, found within the *photosystem I light-gathering centre of photosynthesis. Other ordinary chlorophyll a molecules are also present and these absorb light energy and pass it to P700, creating a charged form, P700+. Electron transfer occurs from photosystem II, electrons being passed on ultimately to produce NADPH, the reduced form of *NADP. See also P680.