Cellular Respiration and Hypoxia

Importance of Oxygen

• Oxygen is essential for survival; every cell in the body requires it.
• Cells use oxygen to produce energy in the form of ATP (adenosine triphosphate), known as the "molecular unit of currency" for intracellular processes.

Mitochondria and ATP Production

• Mitochondria are responsible for ATP production through oxidative phosphorylation.
• Oxygen serves as an electron acceptor in the final steps of oxidative phosphorylation.

Hypoxia

• Hypoxia: A condition where there is less oxygen than normal, affecting ATP production.

Cellular Consequences of Hypoxia

Sodium-Potassium Pump

• ATP is required for the sodium-potassium pump to function.
• Without ATP, sodium accumulates inside the cell, attracting water and causing cell swelling.
• Cell swelling affects microvilli, reducing surface area and absorption.
• Leads to cellular blebbing due to cytoskeleton failure.

Rough Endoplasmic Reticulum (ER)

• Swelling affects the rough ER leading to detachment of ribosomes, reducing protein synthesis.

Anaerobic Glycolysis

• Backup ATP production via anaerobic glycolysis occurs, producing only 2 ATP per glucose and generating lactic acid as a byproduct.
• Lactic acid decreases pH, potentially denaturing proteins and enzymes.

Potential for Reversibility

• Cellular changes are potentially reversible if oxygen is restored in time.
• Prolonged hypoxia leads to irreversible damage.

Irreversible Damage

Calcium Pump Failure

• Calcium build-up activates unwanted enzymes:
  • Proteases: Damage the cytoskeleton.
  • Endonucleases: Cut up DNA.
  • Phospholipase: Destroys cell membranes.

Lysosomal Membrane Damage

• Lactic acid and calcium can damage lysosomal membranes, releasing hydrolytic enzymes that digest the cell.

Mitochondrial Damage

• Calcium influx increases mitochondrial membrane permeability, causing cytochrome c to leak into the cytosol.
• This triggers apoptosis (programmed cell death).

Conclusion

• Lack of oxygen or hypoxia leads to a cascade of cellular failures and potential cell death.