Light independant (2)

• Calvin cycle

  Calvin cycle

  
• Carbon fixation


  • Carbon dioxide (1C) and RUBP (5C) make (6C) compound
  • Rubisco catalyst
  • (6C) compound makes 2 molecules of GP (3C)
• GP reduction


  • ATP and NADPH provide energy and protons to reduce glycerate-3-phosphate (GP) to triose phosphate (TP)
  • 5/6 TP recycles and reforms RuBP
  • 1/6 TP forms carbohydrates such as starch
• RuBP regeneration

  • 2 triose phosphate (TP) combine to reform ribulose bisphosphate (RuBP)
  • Uses energy from ATP
• What are the 3 light independant reaction steps?

  • Carbon fixation
  • GP reduction
  • RuBP regeneration
• Question

  • NADPH and ATP from the light dependant reaction are needed to reform RuBP
  • In the dark this cannot happen
  • GP does not need this so will still be made

  
• How to test for light-independant reaction?

  • Put leaf in flask with radioactive carbon dioxide
  • Analyse light independant products for radioactive carbon
  • Positive result shows CO2 was used in calvin cycle   
• What happens in the light independant reaction? 

  • RuBP combines with carbon dioxide to make a 6 carbon compound using a rubisco catalyst
  • The 6 carbon compound is split into 2 molecules of GP 
  • GP is reduced into TP by energy from ATP and a proton donated by NADPH reforming NADP
  • TP is used in other molecules or 2 TP molecules combine to reform RUBP with energy from ATP