Sol –
Oxygen (O₂) Transport:
- Primary Carrier: Hemoglobin in red blood cells (RBCs).
- Structure: Hemoglobin has 4 polypeptide chains with a heme group (Fe²⁺), which binds 1 O₂ molecule.
- Reversible Binding: O₂ binds in the lungs (high pO₂) to form oxyhemoglobin; it is released in tissues (low pO₂) where O₂ is needed.
- Oxygen-Hemoglobin Dissociation: Influenced by factors like ↑CO₂, ↓pH, ↑temperature (Bohr Effect), causing reduced O₂ affinity.
Carbon Dioxide (CO₂) Transport:
- Carbaminohemoglobin (20-25%): CO₂ binds to hemoglobin to form carbaminohemoglobin.
- Bicarbonate Ion (70%): CO₂ in tissues combines with water to form carbonic acid, which dissociates into bicarbonate ions (HCO₃⁻) and hydrogen ions (H⁺), with chloride shift occurring (Cl⁻ enters RBCs).
- Dissolved in Plasma (5-7%): A small amount of CO₂ is dissolved directly in plasma.
In the lungs, bicarbonate ions are converted back to CO₂ and expelled during expiration.
