Final answer:
In the light-dependent reactions of photosynthesis, electrons are excited in photosystem II by absorbed light, passed along the electron transport chain via the cytochrome complex, and eventually transferred to photosystem I to reduce NADP+ to NADPH.
Step-by-step explanation:
The pathway of electron transfer from photosystem II (PSII) to photosystem I (PSI) during the light-dependent reactions of photosynthesis involves several key steps. When photons strike PSII, they are absorbed by pigments and the energy is passed to chlorophyll a molecules, exciting electrons. These high-energy electrons are then passed to the electron transport chain (ETC). In the ETC, the excited electrons are transferred to the cytochrome complex, which then helps pump protons across the thylakoid membrane, creating a proton gradient. The electrons are eventually transferred to PSI. Within PSI, the electrons are re-energized by light absorption and finally passed to NADP+ to form NADPH, a carrier of reducing power for the Calvin cycle which is used to produce glucose.