Light dependent reactions

• Light dependent reaction

  A) Protons hit chlorophyll

  B) electrons released

  C) Electrons move across carriers

  D) Light hits water

  E) 2 oxygen

  F) 2 protons

  G) NADP

  H) 2 protons

  I) 2 electrons

  J) reduced NADP

  K) ADP + Pi

  L) ATP

  
• Part A

  • Each chlorophyll contains electrons
  • Protons of light energy hit the chlorophyll
  • Electrons are raised to a higher energy level
  • Pair of electrons are released from the chlorophyll
  • Chlorophyll is oxidised/ ionised- photoionisation
• Part B

  • Electrons move across electron carriers at successively lower energy levels *
  • The carriers become reduced as they accept the electrons
  • Oxidised when the electron moves on
  • * The lost energy is used in chemiosmosis to make ATP
• Part C- Photolysis

  • Photon of light hits a molecule of water
  • Water splits into 3 parts: O2, 2 electrons and 2 protons
  • O2 - used in respiration/ diffuses out of the leaf
  • Electrons - returns to reduced chlorophyll
  • Protons - Used in the reduction of NADP and chemiosmosis
• Part D - reduction of NADP

  • Coenzyme NADP, 2 electrons (from chlorophyll), 2 protons from chemiosmosis/ photolysis
  • Create reduced NADP
• Chemiosmosis in the light dependent reaction

  A) Thylakoid

  B) Chlorophyll

  C) Proton pump

  D) Electron carriers

  E) High H+ concentration

  F) Low H+ concentration

  G) ATP

  H) ATP synthase

  
• Chemiosmosis

  • Electrons (from chlorophyll) power the proton pumps
  • The H+ (from photolysis) are pumped into the thylakoid cavity
  • H+ accumulates, creating a proton gradient
  • Protons move back down the gradient through ATP synthase
  • Releases energy for ADP + Pi to go through an enzyme reaction and create ATP
• End products:

  • Oxygen
  • Reduced NADP
  • ATP