How `CO_(2)` is transported mainly in the blood?

Answer

To understand how carbon dioxide (CO₂) is transported in the blood, we can break down the process into several steps:

### Step-by-Step Solution:

1. **Understanding the Role of Hemoglobin**:
- Hemoglobin is a red pigment found in red blood cells (RBCs) and is crucial for gas transport in the blood.
- It has a high affinity for oxygen, but it can also bind to carbon dioxide.

**Hint**: Remember that hemoglobin is key for transporting gases in the blood.

2. **Formation of Carboxyhemoglobin**:
- When carbon dioxide enters the blood, it can combine with hemoglobin to form a compound known as carboxyhemoglobin (HbCO₂).
- This reaction allows CO₂ to be transported by the hemoglobin in the blood.

**Hint**: Think of carboxyhemoglobin as a special form of hemoglobin that carries CO₂.

3. **Percentage of CO₂ Transported**:
- Approximately 20-25% of carbon dioxide is transported in the blood bound to hemoglobin as carboxyhemoglobin.
- The majority of CO₂, about 70%, is transported in the form of bicarbonate ions (HCO₃⁻).

**Hint**: Keep track of the percentages: 20-25% as carboxyhemoglobin, 70% as bicarbonate.

4. **Bicarbonate Formation**:
- The conversion of CO₂ to bicarbonate occurs primarily in red blood cells.
- The enzyme carbonic anhydrase plays a crucial role in this process. It catalyzes the reaction between carbon dioxide and water to form carbonic acid (H₂CO₃), which then dissociates into bicarbonate and hydrogen ions.

**Hint**: Carbonic anhydrase is the enzyme that facilitates the conversion of CO₂ to bicarbonate.

5. **Dissolved CO₂**:
- The remaining 7-10% of carbon dioxide is transported in the blood in a dissolved state.
- This dissolved CO₂ is directly proportional to the partial pressure of CO₂ in the blood.

**Hint**: Remember that a small percentage of CO₂ is simply dissolved in the plasma.

### Summary:
In summary, carbon dioxide is transported in the blood mainly in three forms:
- About 20-25% is carried as carboxyhemoglobin (bound to hemoglobin).
- Approximately 70% is transported as bicarbonate ions (HCO₃⁻).
- Around 7-10% is dissolved in the plasma.