Describe the Transport Mechanisms of Oxygen and Carbon Dioxide in the Blood
Oxygen Transport
Oxygen is transported from the lungs to tissues mainly by hemoglobin in red blood cells.
- Oxyhemoglobin: About 98.5% of oxygen binds reversibly to hemoglobin forming oxyhemoglobin (HbO₂).
- Dissolved Oxygen: About 1.5% dissolves directly in plasma and is available for immediate use by tissues.
Factors affecting oxygen binding include partial pressure of oxygen (pO₂), pH (Bohr effect), temperature, and levels of 2,3-BPG.
Carbon Dioxide Transport
Carbon dioxide is carried from tissues to the lungs via three mechanisms:
- Bicarbonate Ions (HCO₃⁻): About 70% is converted into bicarbonate ions in RBCs by the enzyme carbonic anhydrase.
- Carbaminohemoglobin: Around 20% binds to hemoglobin at sites different from oxygen, forming carbaminohemoglobin (HbCO₂).
- Dissolved CO₂: Approximately 7–10% is dissolved directly in plasma.
Chloride Shift
As bicarbonate leaves the RBCs, chloride ions enter to maintain ionic balance, a process known as the chloride shift.
Efficient oxygen and carbon dioxide transport is essential for cellular respiration and maintaining acid-base balance in the body.