Significance To optimize photosynthetic performance and minimize photooxidative damage, photosynthetic organisms evolved to efficiently balance light energy absorption and electron transport with cellular energy requirements under constantly changing light conditions. The regulation of linear electron flow (LEF) and cyclic electron flow (CEF) contributes to this fine-tuning. Here we present a model of the formation and structural molecular organization of a CEF-performing photosystem I (PSI)–light harvesting complex I (LHCI)–cytochrome (cyt) b ₆ f supercomplex from the green alga Chlamydomonas reinhardtii . Such a structural arrangement could modulate the distinct operation of LEF and CEF to optimize light energy utilization, despite the same individual structural units contributing to these two different functional modes.