Transportation of Carbon Dioxide in the Body

Carbon dioxide (CO2) is a waste product produced by cells during cellular respiration. It needs to be transported from the tissues, where it is produced, to the respiratory surface, where it can be eliminated from the body. The transportation of carbon dioxide primarily occurs through the circulatory system.

Role of Plasma and Erythrocytes

The main components involved in the transport of carbon dioxide are plasma and erythrocytes (red blood cells). Both of these components work together to ensure efficient transportation of carbon dioxide.

Transportation in Plasma

Plasma is the liquid component of blood that carries various substances, including carbon dioxide. Carbon dioxide can dissolve in plasma, forming carbonic acid (H2CO3) in the presence of the enzyme carbonic anhydrase. This carbonic acid can ionize into bicarbonate ions (HCO3-) and hydrogen ions (H+).

Transportation in Erythrocytes

Erythrocytes play a crucial role in the transportation of carbon dioxide. They contain a protein called hemoglobin, which binds to carbon dioxide. When carbon dioxide enters the erythrocytes, it combines with water to form carbonic acid. This reaction is facilitated by the enzyme carbonic anhydrase present in erythrocytes.

The carbonic acid then dissociates into bicarbonate ions and hydrogen ions. The bicarbonate ions are transported out of the erythrocytes into the plasma in exchange for chloride ions through a protein called the chloride-bicarbonate exchanger. This process is known as the chloride shift.

Transportation from Tissues to Lungs

The transportation of carbon dioxide from tissues to the lungs occurs in two forms:

1. Dissolved CO2: A small fraction of carbon dioxide is transported in its dissolved form in plasma. It diffuses across the capillary walls into the plasma and is carried to the lungs.

2. Bicarbonate ions: The majority of carbon dioxide is converted into bicarbonate ions in the erythrocytes. These bicarbonate ions are then transported in the plasma. In the lungs, carbon dioxide is released from the bicarbonate ions, converted back into carbonic acid, and then into gaseous form. It diffuses out of the plasma and is exhaled during breathing.

Conclusion

In summary, carbon dioxide is primarily transported from tissues to the respiratory surface by plasma and erythrocytes. Plasma carries a small fraction of dissolved carbon dioxide, while erythrocytes play a crucial role in converting carbon dioxide into bicarbonate ions and transporting them. This coordinated effort between plasma and erythrocytes ensures the efficient removal of carbon dioxide from the tissues and its elimination from the body through respiration.

Plasma and erythrocytes