Carbonic anhydrase is mostly active in

Options

A. lymphocytes
B. blood plasma
C. RBC
D. leucocytes

Explanation

**Step-by-Step Solution:**

1. **Understanding Carbonic Anhydrase**: Carbonic anhydrase is an enzyme that plays a crucial role in the transport of carbon dioxide in the body. It catalyzes the conversion of carbon dioxide (CO₂) and water (H₂O) into carbonic acid (H₂CO₃).

2. **Turnover Number**: The enzyme has a high turnover number, approximately 36 million, which means it can convert a large number of substrate molecules into product in a short time (one minute). This indicates its efficiency.

3. **Reaction Catalyzed**: The reaction catalyzed by carbonic anhydrase is:
\[ \text{CO}_2 + \text{H}_2\text{O} \leftrightarrow \text{H}_2\text{CO}_3 \]
Carbonic acid (H₂CO₃) is a weak acid that dissociates into hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻).

4. **Location of Activity**: The maximum activity of carbonic anhydrase occurs in red blood cells (RBCs). This is where the enzyme is predominantly found and where it facilitates the transport of carbon dioxide from tissues to the lungs.

5. **Chloride Shift**: The bicarbonate ions (HCO₃⁻) produced in the RBCs are transported into the plasma, while chloride ions (Cl⁻) move into the RBCs in a process known as the chloride shift. This is essential for maintaining ionic balance and facilitating gas exchange.

6. **Conclusion**: Based on the above information, carbonic anhydrase is most active in red blood cells (RBCs). Other components like plasma, lymphocytes, and leukocytes have minimal or no significant activity of this enzyme.

7. **Final Answer**: Therefore, the correct answer to the question is that carbonic anhydrase is most active in **red blood cells (RBCs)**.

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