Light Independant Reactions

• Carbon fixation


  1. Carbon atoms from CO2 are fixed

  2. This is used to build glucose
• Light Independent Reactions


  • ATP and NADPH from the light dependant reactions are essential for LIR
  • LIR takes place in the stroma of the chloroplast
• Steps of Calvin Cycle

  1. CARBON FIXATION

  2. REDUCTION

  3. REGENERATION
• Calvin Cycle occurs in light independent reactions
• Light independant reactions are a type of coupled reactions
• In carbon fixation, CO2 molecule combines with a 5 carbon acceptor molecule called RuBP
• 3-PGA (3- phosphoglyceric acid)


  3 carbon molecule split from a 6 carbon compound created in carbon fixation
• Rubisco


  Enzyme that acts as a catalyst in carbon fixation
• Rubisco is the most important enzyme on the planet
• ATP and NADPH are used to convert 3-PGA molecules into a sugar molecule called G3P
• The reduction stage is where G3P is made
• NADPH reduces 3PGA molecule to make glyceraldehyde-3-phosphate
• GSP recycling

  GSP are recycled
• G3P utilisation


  1. Some G3P molecules go to make glucose

  2. Others must be recycled to regenerate the RuBP acceptor
• Regeneration

  1. Requires ATP

  2. Involves a complex network of reactions
• In the regeneration stage, some G3P molecules go to make glucose while others are recycled to regenerate RuBP
• Regeneration stage requires ATP(energy)
• Where does carbon fixation occur?

  Stroma
• Where does reduction occur?

  Stroma
• Where does regeneration occur?

  Stroma
• NADPH is in carbon reduction stage