Light reactions: electron flow in photosystems.
  1. Light energy from a photon is passed among chlorophyll molecules.
  2. The energy is eventually captured in an electron from water in Photosystem II.
  3. The splitting of the electron donor, water, releases oxygen.
  4. The electron passes through an electron transport chain (ETC).
  5. The energy from the electron is used to generate ATP.
  6. Another photon excites chlorophyll molecules of Photosystem I.
  7. Energy is passed among electrons to a 2nd ETC.
  8. Energy from this 2nd ETC is stored in the electron acceptor NADPH.