photosynthesis

• where does the light dependent reaction take place

  thylakoid membrane
• two stages of photosynthesis:

  light dependent reaction and light independent reaction
• stages in light dependent reaction

  • photolysis of water
  • photoionisation of chlorophyll
  • chemiosmosis
• photolysis of water

  light energy absorbed by chlorophyll splits water into oxygen, H+ and e-
• equation for photolysis of water

  • H20 ---> 2H+ + 2e- +1/2 O2
• photoionisation 

  light energy is absorbed by chlorophyll and is picked up by electrons which excites them and releases themselves from the chlorophyll molecule.
• chemiosmosis

  • electrons from photoionisation pass through proteins embedded in the membrane ( electron transfer chain)
  • as electrons move - energy is released which is used to actively transport the H+ ions into the thylakoid lumen 
  • electrochemical gradient formed  - more protons in thylakoid lumen than stroma
  • H+ ions go through ATP synthase, shape changes which catalyses the reaction to form ATP
  • H+ combines with coenzyme NADP to form reduced NADP
• where does light independent reaction take place

  stroma
• calvin cycle:

  • co2 reacts with RuBp using enzyme rubisco to form 2 x GP
  • Gp is reduced to Tp using ATP and reduced NADP picks up the H+
  • 1 molecule of carbon would be removed to form useful organic substances - occurs 6 times to make hexose sugar
  • rest of the molecule regenerates RuBp
• limiting factors of photosynthesis:

  temperature, co2 conc, light intensity
• limiting factor: temperature

  affects light independent reaction - enzyme controlled reaction
• limiting factor: co2 concentration

  affects light independent reaction - in the calvin cycle
• limiting factor: light intensity

  affects light dependent reaction -  photoionisation & photolysis
• products of light dependent reaction

  • reduced NADP
  • ATP
  • O2