Figure 22.22 Cyclic photophosphorylation. (A) A scheme showing the energetic basis for cyclic photophosphorylation. (B) In this pathway, electrons from reduced ferredoxin are transferred to cytochrome b6 f rather than to ferredoxin-NADP+ reductase. The flow of electrons through cytochrome b6 f pumps protons into the thylakoid lumen. These protons flow through ATP synthase to generate ATP. Neither NADPH nor O2 is generated by this pathway.