Photosynthesis Lecture Notes

Introduction

• Topics today: Photosynthesis, focusing on the light-dependent and light-independent (Calvin cycle) phases.
• Importance of understanding the photosynthesis equation and its components.
• Balanced equation is crucial for understanding the process fully.

Photosynthesis Equation

• Components required: Carbon dioxide, water.
• Non-material requirements: Sunlight (energy), chlorophyll (substance).
• Products: Glucose (sugar) for energy, oxygen as a byproduct.

Structure of Chloroplast

• Thylakoids: Site of light-dependent reactions, look like stacked coins.
• Stroma: Liquid part inside chloroplast, site of the Calvin cycle.

Process Overview

• Light-Dependent Reaction: Occurs in thylakoids, uses sunlight to split water into hydrogen and oxygen (photolysis).
• Calvin Cycle: Occurs in stroma, uses products of light-dependent phase to produce glucose.

Light-Dependent Phase

• Location: Thylakoids.
• Process:
  • Photolysis: Sunlight splits water into hydrogen and oxygen.
  • Oxygen is released as a gas for respiration.
  • Hydrogen: Attached to NADP to form NADPH.
  • Excitable Electron: Used in photophosphorylation to transform ADP into ATP.
  • End Products: NADPH (hydrogen carrier) and ATP (energy carrier).

Calvin Cycle (Light-Independent Phase)

• Location: Stroma.
• No light required, occurs mostly at night or low light.
• Process:
  • Starts with ribulose bisphosphate (RuBP), a 5-carbon molecule.
  • Combines with carbon dioxide to form an unstable 6-carbon molecule.
  • Breaks into two 3-carbon PGA molecules.
  • ATP provides energy, NADPH provides hydrogen.
  • Formation of PGAL (3C compound), which can become glucose or reform RuBP.
  • End Products: Glucose (sugar), regeneration of RuBP.
  • Recycling: ADP and phosphate, NADP return to the light-dependent phase.

Key Terminology

• Photolysis: Splitting water with light into hydrogen and oxygen.
• NADPH: Hydrogen carrier.
• ATP: Energy carrier, formed via photophosphorylation.
• Photophosphorylation: Using light to add phosphate to ADP to form ATP.
• PGAL: Precursor to glucose, formed in Calvin cycle.

Conclusion

• Regular cycles between light-dependent and independent phases.

• Importance of sunlight period for plants to complete the full photosynthesis cycle.

• Reminder: Make sure to review the concepts and terminology regularly for better understanding.