Oxygen and Cellular Function

Importance of Oxygen

• Every cell requires oxygen to produce energy.
• Energy is produced in the form of ATP (adenosine triphosphate).
• ATP is critical as it powers cellular activities, similar to a currency in a factory.

Mitochondria and ATP Production

• Mitochondria produce ATP through oxidative phosphorylation.
• Oxygen is essential for this process as an electron acceptor.
• Lack of oxygen leads to hypoxia, impairing ATP production and threatening cell survival.

Consequences of ATP Depletion

• Without ATP, cellular processes falter.
• Sodium-potassium pumps on cell membranes stop functioning, disrupting ion gradients.
  • Sodium influx causes water retention, leading to cell swelling.
  • Swelling reduces microvilli surface area, impairing absorption.
  • Structural framework (cytoskeleton) begins to fail, possibly causing blebbing.
  • Rough endoplasmic reticulum swells; ribosomes detach, reducing protein synthesis.

Anaerobic Glycolysis

• Backup process: anaerobic glycolysis provides minimal ATP in absence of oxygen (2 ATP per glucose).
• Produces lactic acid as a byproduct, lowering cell pH and potentially denaturing proteins.
• Cellular changes due to hypoxia are reversible if oxygen supply is quickly restored.

Irreversible Cell Damage

• Prolonged hypoxia leads to irreversible damage.
• Calcium accumulation:
  • Activates unwanted enzymes (proteases, endonucleases, phospholipases), damaging the cytoskeleton and DNA.
  • Disrupts lysosomal membranes; hydrolytic enzymes leak and digest the cell internally.
  • Increased cytosolic calcium may prompt mitochondria to release cytochrome c, triggering apoptosis (programmed cell death).

Summary

• Lack of oxygen (hypoxia) initiates a cascade of cellular failures.
• Early intervention can reverse damage; however, prolonged oxygen deprivation can lead to irreversible cellular destruction and apoptosis.