Lecture on The Cori Cycle

Introduction

• Topic: Carbohydrate Metabolism
• Focus: Cori Cycle
• Presenter: Shomus Biology

Overview of Cellular Respiration

• Metabolism: Cellular respiration in presence/absence of oxygen.
  • Aerobic Respiration:
    • Occurs in presence of oxygen.
    • Process: Glucose → Pyruvate → Acetyl-CoA → TCA Cycle → NADH/FADH2 → ATP (energy).
  • Anaerobic Respiration:
    • Occurs in absence of oxygen.
    • Common during intense exercises.
    • Key tissues: Liver and Muscles.

Muscle Cell Metabolism During Oxygen Absence

• Glucose Utilization:

  • Glucose → Pyruvate (glycolysis) without oxygen.
  • No TCA cycle due to absence of terminal electron acceptor (oxygen).
  • Pyruvate accumulates.

• Lactate Formation:

  • Enzyme: Lactate Dehydrogenase.
  • Conversion: Pyruvate → Lactate (Lactic Acid).
  • Issue: Lactic acid buildup and low ATP production (2 ATP per glucose).

The Cori Cycle

• Purpose: Address pyruvate/lactate buildup and ATP shortage in muscles.
• Process Overview:
  • Transport lactic acid from muscles to liver via bloodstream.
  • In Liver:
    • Lactic Acid → Pyruvate (via Lactate Dehydrogenase).
    • Pyruvate → Glucose (via Gluconeogenesis).
  • Transport glucose back to muscles.
  • Muscles utilize glucose for energy (glycolysis, TCA cycle, electron transport chain).

Energetics of The Cori Cycle

• Energy Costs:
  • Glucose → Pyruvate yields 2 ATP.
  • Pyruvate → Glucose in liver consumes 6 ATP.
  • Despite energy cost, process is essential for muscle function.

Further Details

• Lactic Acid Fermentation:
  • Conversion of glucose to lactic acid when ATP demand exceeds oxidative phosphorylation.
• Glycolysis and Gluconeogenesis in Liver:
  • Requires ATP and GTP hydrolysis.
  • Glucose transported to muscles can also be stored as glycogen.

Conclusion

• Cori cycle helps maintain energy supply during anaerobic conditions.
• Important for muscle energy production during intense physical activity.
• Further details on sequential stages available in second part of the lecture series.