text: Electrons are often removed from the electron transport chains to charge NADP with electrons, reducing it to NADPH. Like ATP synthase, ferredoxin-NADP reductase, the enzyme that reduces NADP, releases the NADPH it makes into the stroma, right where it is needed for the dark reactions.
  Because NADP reduction removes electrons from the electron transport chains, they must be replaced—the job of photosystem II, which splits water molecules (HO) to obtain the electrons from its hydrogen atoms.