elektronide liikumine ümber fotosüsteemi I tema aktseptorpoolelt (ferredoksiin, Fd) cytb6f kompleksi vahendusel tagasi P700-le ja ferredoksiinile, In cyclic photophosphorylation, cytochrome b6f uses the energy of electrons from not only photosystem II but also photosystem I to create more ATP and to stop the production of NADPH. Cyclic phosphorylation is important to create ATP and maintain NADPH in the right proportion for the light-independent reactions.