Approximately `70%` of carbon dioxide absorbed by the blood will be transported to the lungs

Options

A. as bicarbonate ions
B. in the form of dissolved gas molecules
C. by binding to RBC
D. as carbaminohemoglobin

Answer

To answer the question regarding the transport of carbon dioxide (CO2) in the blood, we can break down the process into several steps:

### Step-by-Step Solution:

1. **Understanding Carbon Dioxide Transport**:
- Carbon dioxide is a waste product of cellular respiration and needs to be transported from the tissues to the lungs for exhalation.

2. **Forms of CO2 Transport**:
- CO2 is transported in the blood in three main forms:
- As bicarbonate ions (HCO3^-)
- Bound to hemoglobin as carbaminohemoglobin
- Dissolved in plasma as gas molecules.

3. **Percentage of CO2 Transport**:
- Approximately 70% of the CO2 absorbed by the blood is transported as bicarbonate ions. This conversion occurs primarily in red blood cells (RBCs).

4. **Formation of Bicarbonate**:
- Inside the RBCs, CO2 combines with water (H2O) to form carbonic acid (H2CO3) through the action of the enzyme carbonic anhydrase.
- Carbonic acid then dissociates into bicarbonate ions (HCO3^-) and hydrogen ions (H+).

5. **Transport to the Lungs**:
- The bicarbonate ions are then transported in the plasma to the lungs, where they will be converted back to CO2 for exhalation.

6. **Other Forms of Transport**:
- The remaining CO2 is transported:
- About 20-23% is bound to hemoglobin as carbaminohemoglobin.
- A small percentage (about 7-10%) is dissolved directly in the plasma.

7. **Conclusion**:
- Therefore, it can be concluded that approximately 70% of carbon dioxide absorbed by the blood is transported to the lungs as bicarbonate ions.