Understanding CO2 Transport in Blood
When carbon dioxide (CO2) is transported in the blood, it exists in three primary forms: dissolved in plasma, bound to hemoglobin, and as bicarbonate ions (HCO3-).
Forms of CO2 Transport:
- Dissolved CO2: About 7% of CO2 is transported in its dissolved form in the plasma.
- Carbamino Compounds: Approximately 23% of CO2 binds to hemoglobin and other proteins, forming carbamino compounds.
- Bicarbonate Ions: The majority, around 70%, of CO2 is converted into bicarbonate ions (HCO3-) in the red blood cells. This process occurs through the action of the enzyme carbonic anhydrase.
Role of Bicarbonate in CO2 Transport:
- Conversion Process: CO2 enters red blood cells and reacts with water, forming carbonic acid (H2CO3). This acid quickly dissociates into bicarbonate (HCO3-) and hydrogen ions (H+).
- Buffering System: The formation of bicarbonate is crucial for maintaining the blood's pH. The bicarbonate acts as a buffer, helping to balance acidity in the blood.
- Transport to Lungs: When blood reaches the lungs, bicarbonate is converted back to CO2, which is then expelled during exhalation.
Conclusion:
The significant portion of CO2 in the form of bicarbonate is essential for efficient gas exchange and maintaining acid-base balance in the body. This is why the correct answer to the question about the percentage of CO2 that flows in blood as bicarbonate is indeed 70%.