Figure 22.20 The pathway of electron flow from H2O to NADP+ in photosynthesis. This endergonic reaction is made possible by the absorption of light by photosystem II (P680) and photosystem I (P700). Abbreviations: Ph, pheophytin; QA and QB, plastoquinones; Pc, plastocyanin; A0 and A1, acceptors of electrons from P700*; Fd, ferredoxin; WOC, water-