Light independent reaction

• What are the two main inputs from the light-dependent stage to the light-independent stage of photosynthesis?

  Energy from ATP and hydrogen from reduced NADP
• What is the purpose of the energy and hydrogen passed to the Calvin cycle?

  They are used to produce complex organic molecules, including carbohydrates
• What are some carbohydrates produced during the Calvin cycle?

  • Starch (for storage)
  • Sucrose (for translocation around the plant)
  • Cellulose (for making cell walls)
• Why is the Calvin cycle referred to as light-independent?

  It does not require energy from light and can occur in light or darkness
• Why can't the Calvin cycle continue indefinitely in darkness?

  Because it requires inputs of ATP and reduced NADP from the light-dependent stage, which will run out
• What are the three main steps within the Calvin cycle?

  1. Carbon fixation
  2. Reduction of glycerate 3-phosphate
  3. Regeneration of ribulose bisphosphate
• What enzyme catalyzes the fixation of carbon dioxide in the Calvin cycle?

  Rubisco (ribulose bisphosphate carboxylase)
• What is the result of the reaction between carbon dioxide and ribulose bisphosphate (RuBP)?

  It yields two molecules of glycerate 3-phosphate (GP)
• What is the carbon count of glycerate 3-phosphate (GP)?

  3C (three-carbon compound)
• What happens to glycerate 3-phosphate (GP) in the Calvin cycle?

  It is reduced to triose phosphate (TP) using ATP and reduced NADP
• What is the three-carbon sugar produced from glycerate 3-phosphate (GP)?

  Triose phosphate (TP)
• What can triose phosphate (TP) be used to produce in plants?

  • Hexose phosphates (6C) for starch, sucrose, or cellulose
  • Glycerol and fatty acids for lipids
  • Amino acids for protein synthesis
• How is ribulose bisphosphate (RuBP) regenerated in the Calvin cycle?


  It is regenerated from triose phosphate (TP) using ATP
• What are the intermediate molecules of the Calvin cycle?

  • Glycerate 3-phosphate (GP)
  • Triose phosphate (TP)
• What is glycerate 3-phosphate (GP) used to produce?

  Some amino acids
• What is triose phosphate (TP) used to produce?

  Hexose phosphates, lipids, and amino acids
• What fraction of TP is used to regenerate RuBP

  5/6
• Process of Carbon Fixation:

  1. Co2 combines with RuBP (catalysed by rubisco)
  2. Produces unstable 6C compound and splits into 2 GP molecules
  3. The Co2 becomes 'Fixed' (removed from external environments)