Bulk of carbon dioxide `(CO_(2))` released from body tissues into the blood is present as

Options

A. bicarbonate in blood plasma and rbcs
B. free `cO_(2)` in blood plasma
C. 70% carbamino haemoglobin and 30 % as bicarbonate
D. carbamino haemoglobin in RBCs

Answer

To answer the question regarding how the bulk of carbon dioxide (CO₂) released from body tissues into the blood is present, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Carbon Dioxide Transport**: Carbon dioxide is produced in the tissues as a byproduct of cellular respiration. Once produced, it needs to be transported to the lungs for exhalation.

2. **Modes of Transport**: CO₂ is transported in the blood in three main forms:
- As bicarbonate ions (HCO₃⁻)
- As carbamino compounds (bound to hemoglobin)
- Dissolved in plasma

3. **Bicarbonate Formation**: The majority of CO₂ (approximately 70%) is converted into bicarbonate ions in the red blood cells (RBCs). This reaction is catalyzed by the enzyme carbonic anhydrase, which facilitates the conversion of CO₂ and water into carbonic acid (H₂CO₃), which then dissociates into bicarbonate and hydrogen ions.

4. **Carbamino Compounds**: About 20-30% of CO₂ binds to hemoglobin and other proteins to form carbamino compounds. This process involves the binding of CO₂ to the amino groups of hemoglobin, forming carbaminohemoglobin.

5. **Dissolved CO₂**: A small percentage (around 5-10%) of CO₂ is transported dissolved directly in the plasma.

6. **Conclusion**: Given that the bulk of CO₂ is present as bicarbonate ions in the blood plasma and red blood cells, the correct answer to the question is that the majority of CO₂ released from body tissues into the blood is present as bicarbonate.

### Final Answer:
The bulk of carbon dioxide (CO₂) released from body tissues into the blood is present as bicarbonate in blood plasma and RBCs.

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