Following the excitation of P700, one of its electrons is passed on to an electron acceptor, A, triggering charge separation producing an anionic A and cationic P700. Subsequently, electron transfer continues from A to a phylloquinone molecule known as A, and then to three iron-sulfur clusters.
Type I photosystems use iron-sulfur cluster proteins as terminal electron acceptors. Thus, the electron is transferred from F to another iron sulfur cluster, F, and then passed on to the last iron-sulfur cluster serving as an electron acceptor, F. Eventually, the electron is transferred to the protein ferredoxin, causing it to transform into its reduced form, which subsequently finalizes the process by reducing NADP to NADPH.