Photosynthesis Lecture Notes

Introduction

• Welcome to Miss Angler's Biology Classroom.
• Topic: Photosynthesis focusing on the light-dependent phase and the Calvin cycle (light-independent phase).
• Reminder to familiarize with the balanced photosynthesis equation.
• Equation components: Carbon dioxide, water, sunlight, chlorophyll.
• Ultimate products: Glucose (energy) and oxygen (byproduct).

Photosynthesis Equation

• Importance of a balanced equation.
• Common components:
  • Carbon dioxide (CO₂)
  • Water (H₂O)
  • Sunlight (energy, not a material)
  • Chlorophyll (not absorbed by plants but necessary)
• Results in:
  • Glucose (C₆H₁₂O₆)
  • Oxygen (O₂)

Chloroplast Structure

• Light-dependent reactions occur in thylakoids (coin-like structures).
• Calvin cycle occurs in stroma (liquid filling of chloroplast).

Light-Dependent Phase

• Occurs during the day in the thylakoids.
• Involves photolysis: splitting water into hydrogen and oxygen using light.
• Products:
  • Oxygen released as gas for respiration.
  • Hydrogen utilized in further reactions.
  • Excitable electrons from hydrogen used in photophosphorylation.
• Key Processes:
  • NADP picks up hydrogen becoming NADPH.
  • Formation of ATP from ADP by photophosphorylation.

Light-Independent Phase (Calvin Cycle)

• Occurs at night or low light levels in the stroma.
• Begins with ribose biphosphate (RuBP) combining with CO₂ from the atmosphere.
• Forms an unstable 6-carbon compound which splits into 3-carbon PGAs.
• PGAs converted into PGAL using:
  • ATP for energy.
  • NADPH for hydrogen.
• PGALs:
  • Can become glucose.
  • Most return to reform RuBP, continuing the cycle.

Recap

• Light-Dependent Phase:
  • Collect sunlight in thylakoids.
  • Photolysis: Water split into hydrogen and oxygen.
  • Formation of NADPH and ATP.
• Calvin Cycle:
  • Occurs in stroma, no light required.
  • Uses RuBP and CO₂ to form PGAL.
  • PGAL can turn into glucose or reform RuBP.
• Continuous cycle supported by sunlight and chloroplast components.

Conclusion

• Summary of key terms and processes.
• Importance of understanding chemical reactions and their locations.
• Reminder to subscribe and turn on notifications for future lessons.