Lecture on Light-Independent Stage of Photosynthesis

Overview

• Topic: Light-independent stage of photosynthesis (Calvin Cycle)
• Location: Stroma of the chloroplast
• Uses products from the light-dependent stage: NADPH and ATP

Key Processes

Carbon Fixation

• Initial Compound: 5-carbon compound called RuBP (Ribulose bisphosphate)
• Process: Carbon dioxide (CO2) from the stomata diffuses into the chloroplast.
  • CO2 combines with RuBP to form two molecules of GP (3-carbon compound)
  • Enzyme Used: RuBisCO
  • Factors affecting RuBisCO: Temperature, enzyme efficiency (not very efficient)

Formation of TP

• Conversion: GP (Glycerate 3-phosphate) is converted into TP (Triose phosphate)
  • Hydrogen & Electron Source: NADPH from the light-dependent reaction
  • Phosphorylation: GP gains an inorganic phosphate from ATP
  • Result: Formation of ADP which returns to the light-dependent stage

Product Regeneration

• Current State: Two molecules of TP (each 3-carbon), totaling six carbons
• Process: One carbon is removed to form products like glucose, starch, cellulose, lipids, amino acids, etc.
  • Regeneration: The remaining 5 carbons are regenerated into RuBP

Important Terminology

• Calvin Cycle: Another name for the light-independent stage

Summary

• Occurs in stroma, uses products from light-dependent reaction: NADPH and ATP
• Carbon fixation with RuBisCO, formation of TP, and product regeneration
• Generates sugars and other compounds essential for the plant

Exam Tips

• Use correct terminology: RuBP, GP, TP, NADPH, ADP, ATP, RuBisCO, Calvin Cycle
• Understand the sequence and factors affecting the Calvin Cycle processes

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Good luck with your exam!