Figure 10.9 Photophosphorylation In the thylakoid membrane, electrons are passed from photosystem II to photosystem I via a series of electron carriers, including plastoquinone (PQ), cytochrome (Cyt), and plastocyanin (PC). From photosystem I the electrons are passed to ferredoxin (Fd) and then to NADP⁺ reductase. This process results in a proton gradient across the membrane, which drives ATP synthesis. Compare this illustration with Figure 9.8, where a similar process is depicted in mitochondria.