During the light reactions, radiant energy is converted to chemical energy in ATP and NADPH.

  Water molecules provide a supply of low energy electrons to photosystem II.  In a PHOTOLYSIS reaction, the pigments remove electrons from water.  The water molecules break apart releasing H⁺ and O atoms.  The oxygen atoms combine to form O₂ .  Radiant energy energizes these electrons,  This chemical energy is used to activate proton pumps and produce a H⁺ gradient.  ATP is produced by chemiosmosis.

  Photosystem I receives low energy electrons, energizes them and passes them on to NADPH.