Foundations of Biology Exam 1 Practice Test 2026 – Comprehensive Study Resource

Photophosphorylation is the production of ATP driven by a light-generated proton gradient across the thylakoid membrane. Both cyclic and non-cyclic electron transport contribute to creating that gradient. In non-cyclic transport, electrons flow from water through photosystems II and I to NADP+, pumping protons along the way and yielding ATP and NADPH. In cyclic transport, electrons from photosystem I are cycled back to the plastoquinone pool, still pumping protons across the membrane to generate ATP, but no NADPH is formed. Because both pathways ultimately power ATP synthesis via chemiosmosis, they drive photophosphorylation. Other listed processes aren’t powered by light-driven proton gradients: glycolysis and fermentation occur without the chloroplast ATP synthase, and transcription is a cellular process for making RNA rather than energy production.