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