Carbon dioxide transport in the human body?
Explain why the majority of the carbon dioxide is transported in the forms of bicarbonate ions.
Carbon dioxide (CO2) is a waste product produced during cellular respiration in the cells of our body. It needs to be transported from the tissues to the lungs, where it can be expelled from the body. The majority of CO2 is transported in the form of bicarbonate ions (HCO3-) through a process called the bicarbonate buffering system.
Here's how the bicarbonate buffering system works:
1. Carbon dioxide diffuses out of the cells and into the surrounding fluids, like plasma, in the tissues.
2. Once in the plasma, carbon dioxide combines with water (H2O) to form carbonic acid (H2CO3) through an enzyme called carbonic anhydrase. This reaction occurs rapidly and is reversible.
CO2 + H2O ⇌ H2CO3
3. Carbonic acid (H2CO3) dissociates into a hydrogen ion (H+) and a bicarbonate ion (HCO3-).
H2CO3 ⇌ H+ + HCO3-
4. Bicarbonate ions (HCO3-) formed in the reaction above are negatively charged and can easily move through the bloodstream.
5. To maintain electrical neutrality, chloride ions (Cl-) move into the red blood cells as bicarbonate ions (HCO3-) move out. This exchange occurs through a protein called the chloride-bicarbonate exchanger.
6. In the lungs, carbon dioxide is released from the body when bicarbonate ions (HCO3-) recombine with hydrogen ions (H+) to form carbonic acid (H2CO3), which then dissociates into carbon dioxide (CO2) and water (H2O).
H+ + HCO3- ⇌ H2CO3 ⇌ H2O + CO2
7. Finally, carbon dioxide diffuses out of the bloodstream into the alveoli of the lungs and is expelled from the body when we exhale.
The majority of carbon dioxide is transported as bicarbonate ions because they are highly soluble and can easily move through the bloodstream. Additionally, the bicarbonate buffering system helps maintain the acid-base balance in the body by regulating the levels of hydrogen ions (H+) and bicarbonate ions (HCO3-). This mechanism allows for efficient transportation and elimination of carbon dioxide while ensuring proper pH levels in the body.