Photosynthesis

• Equation for Photosynthesis


  6CO2 + 6 H2O —> 6O2 + C6 H12 O6
• What are the 2 main stages of photosynthsis

  1. Light Dependant Reaction
  2. Light Independent Reaction
• What happens in the light dependant reaction?

  1. Photolysis
  2. Photoionisation
  3. Chemiosmosis
• What is Photolysis?


  The breaking apart of water molecules into protons and electrons using light energy.
• What is Photoionisation?


  The chlorophyll absorbs the light energy causing the electrons to become excited and go up an energy level, passing onto the first electron acceptor at the start of the ETC. This reduces the chlorophyll.
• The electron transport chain


  Once the electron enters the ETC it moves down the electron carriers through a series of oxidation and reducation reactions. As they pass down the ETC they give of energy, this energy is used to pump H+ into the thylakoid space, via the proton pump.
• Chemiosmosis 


  H+ a pumped into the thylakoid space via active transport through the proton pump. There is a higher conc of H+ in the Thylakoid space then there is in the stroma. This caused the flow of H+ through facilitated diffusion into the stroma via the ATP synthase channel. This movement of H+ causes the phosphorylation of ATP. NADP used the H+ as they enter the stroma to become NADPH
• What particles are taken from the LDR to the LIR

  1. ATP
  2. NADPH
• The Calvin Cycle

  1. RuBP combines with CO2 from the atmosphere. This reaction is catalysed by the enzyme Rubisco. This creates an unstable 6 carbon molecules
  2. The 6 carbon molecule then splits into 2x G3P
  3. G3P is then reduced into triose Phosphate - G3P is reduced as NADPH is oxidised, this is also uses ATP, both from LDR
  4. Triose phosphate then gives off 1 C to be made into an organic compound. The remaining 5C are used to regenerate RuBP using ATP
  5. After 6 cycles on glucose is formed
• What factors affect the rate of photosynthesis

  1. Light Intensity
  2. Concentration of CO2
  3. Temperature
• How are plants adapted to photosynthesis?

  1. Large SA to absorb a lot of light, as there is a larger area for light to reach
  2. The palisade area contains a large number of chlorophyll as this area of the leaf has the most sunlight
  3. The mesophyll layer contains air spaces to allow for easier diffusion of gases
  4. Thin - short diffusion pathway
  5. Has a good vein connections to allow xylem and phloem to transport water and nutrients