Thylakoid membrane (lumen ↔ stroma)

Light reactions of photosynthesis mnemonics

Two photons per electron: water in at PSII, NADPH out at PSI.

Which photosystem does what

PSII splits H₂O (the 2s go together); PSI makes NADPH. And 680 runs before 700.

A mnemonic only sticks once you have used it. The quiz and the rebuild below both draw on these exact steps.