Question

Which of the following are ways CO2 is transported in the blood?

• A. As bicarbonate (HCO3–)

• B. As dissolved C02 in plasma

• C. As carbaminohemoglobin

• D. All of the above

• E. None of the above

Answer 1

The answer is option D (all of the above)

There are three ways for CO₂ transportation in blood.

1. Carried as bicarbonate ion (70%)

2. Binds to hemoglobin (20%)

3. Directly dissolves in blood (10%)

Carried as bicarbonate ion :

About 70% of CO₂ is transported by this mechanism. CO₂ diffuses into red blood cells (RBC'S) and combines with water in presence of carbonic anhydrase enzyme to produce bicarbonate ions.

Bicarbonates will accumulates in erythrocytes through this process and due to high concentration of bicarbonates inside the RBC's than surroundings, the bicarbonate ions travels into the blood plasma. Then CO₂ is transported to the lungs through blood stream. This process reverses at pulmonary capillaries and produces CO₂. This CO₂ is exhaled by pulmonary ventilation.

Binds to hemoglobin:

About 20% of CO₂ binds with globin portion of hemoglobin and forms carbaminoglobin. Carbon dioxide enters into the blood and then diffuses into erythrocytes, where it combines with globin portion of hemoglobin.

This reaction reverses at pulmonary capillaries and produces CO₂ which then exhaled through pulmonary ventilation.

Directly dissolves in blood:

About 10% of CO₂ is transported by this mechanism. Carbon dioxide is slightly soluble in blood. Tissues will consume oxygen for metabolism and produces carbon dioxide, which is then, diffuses into the blood plasma and dissolves in it. Then it travels to the pulmonary capillaries in blood stream, diffuses across the respiratory membrane into alveoli and exhaled to outside.