3.5.1

• Photoionisation

  Chlorophyll pigment absorbs light.

  • Energy from light excites the highest energy electrons, so they escape the pigment.
  • Some of the energy from electrons released is conserved in the production of ATP and reduced NADP
• Photolysis

  Water is hydrolysed by light energy to form 2 protons, 2 electrons and one oxygen.
• Chemiosmotic Theory

  Electrons are brought to the thylakoid membranes by NAPH

  • They are transferred down the electron transfer chain via electron carriers from the stroma to the thylakoid space; each of a lower successive energy level so energy is lost.
  • This energy is used to pump H+ ions into the thylakoid space from the stroma via active transport using Hydrogen pumps.
  • H+ ions move through ATP synthase via facilitated diffusion back into the Stroma, with the energy released used to produce ATP.
• Electrons at the end of the electron transfer chain reduce NAPH to be used in the Calvin Cycle.
• The movement of H+ ions through ATP Synthase is called chemiosmosis.
• Light Dependent Reaction occurs in the thylakoid space
• Light Independent Reaction occurs in the stroma