LIGHT INDEPENDENT REACTION

• Light independent reaction or the Calvin cycle is temperature sensitive due to it being an enzyme controlled reaction - occurs in the stroma of the chloroplast
• from LDR:

  • reduced NADPH = donates the hydrogen to reduce the molecule GP
  • ATP = is hydrolysed to provide energy for the reaction
• 1ST CARBON FIXATION

  1. carbon dioxide reacts with RuBP (ribulose biphosphate) to form 2x of GP (glycerate-3-phosphate which is a 3 carbon compound)

  • this reaction is catalysed by the enzyme rubisco
  • the 6 molecule intermediate is unstable and immediately breaks down 2xGP

  
• 2ND REDUCTION:

  1. 2x GP is reduced to 2x TP (triose phosphate). This reaction requires energy so...

  • 2ATP is hydrolysed into 2ADP
  • 2NADPH transfers its electrons to GP (becoming 2NADP)

  2. one atom of TP leaves to be converted into an organic molecule (glucose = 6 turns of cycle needed to make the hexose sugar)

  
• 3RD REGENERATION:

  1. rest of the TP (5 carbon molecules) is converted/ regnerated back into RuBP. This reaction requires energy so...

  • ATP is hydrolysed into ADP

  
• limiting factors:

  • temp (effect LIR) = enzyme controlled reaction
  • CO2 conc (effect LIR) = one of the reactants in the Calvin cycle
  • light intensity (effect LDR) = needed on photolysis and photoionisation

  farmers can manipulate conditions for maximum growth e.g. artificial light, heating and burning fuels = must make sure costs don't outweigh the benefit