Lecture Notes: Carbon Dioxide Transport in the Blood

Overview

• Oxygen Transport: Oxygen moves from alveolus in lungs to blood in capillaries, then pumped by heart to body cells.
• Cellular Respiration: Cells use oxygen, produce carbon dioxide (CO2) as a byproduct.
• CO2 Removal Necessity: Vital to remove CO2 from cells to prevent toxic buildup.

CO2 Removal Process

1. CO2 Movement:
   • CO2 produced in cells (e.g., brain, toe) during cellular respiration.
   • CO2 needs to move from the cell into the blood capillaries.
2. Establishing Concentration Gradient:
   • Initial movement of CO2 from cells into plasma creates concentration gradient.
   • Movement continues until equilibrium is reached, which is not ideal.
   • Goal: Maintain concentration gradient to facilitate continuous CO2 removal.

Conversion of CO2 in Blood

• Water in Blood:
  • Blood is approximately 92% water, facilitating CO2 transformation.
• Formation of Carbonic Acid (H2CO3):
  • CO2 combines with water (H2O) to form carbonic acid.
  • Reaction: [ CO2 + H2O \rightarrow H2CO3 ]
• Equilibrium with Carbonic Acid:
  • CO2 and H2CO3 maintain equilibrium.

Further Breakdown

• Dissociation of Carbonic Acid:
  • Carbonic acid dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).
  • Reaction: [ H2CO3 \rightarrow H^+ + HCO3^- ]
• Result of Dissociation:
  • Continuous dissociation helps maintain CO2 concentration gradient.
  • Allows more CO2 to convert to carbonic acid and then dissociate.

Importance in CO2 Transport

• Bicarbonate Ion Formation:
  • Approximately 66-67% of CO2 is transported by conversion to bicarbonate ions.
• Concentration Gradient Maintenance:
  • Essential for efficient CO2 transport from cells to blood.
  • Prevents equilibrium by maintaining a gradient for CO2, carbonic acid, and its ions.

Conclusion

• The process converts CO2 to bicarbonate ions, facilitating its removal from blood.
• This process is one of the key mechanisms for CO2 regulation in the body.