In human blood, the oxygen carrier is

Options

A. Carbonic anhydrase
B. Haemoglobin
C. Haemocyanin
D. Both (1) & (3)

Answer

To answer the question "In human blood, the oxygen carrier is," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- Carbonic anhydrase
- Hemoglobin
- Hemocyanin
- Both one and three

2. **Evaluate Carbonic Anhydrase**:
- Carbonic anhydrase is an enzyme that catalyzes the conversion of carbon dioxide (CO2) and water into carbonic acid (H2CO3).
- Its primary role is in the transport of CO2 in the blood, not in the transport of oxygen. Therefore, it is not the oxygen carrier.

3. **Evaluate Hemocyanin**:
- Hemocyanin is a copper-containing protein found in some invertebrates, which serves as an oxygen carrier.
- However, it is not present in humans. Thus, it cannot be the oxygen carrier in human blood.

4. **Evaluate Hemoglobin**:
- Hemoglobin is a protein found in red blood cells (RBCs) of vertebrates, including humans.
- It binds to oxygen in the lungs and carries it to tissues throughout the body.
- Hemoglobin is well-known as the primary oxygen carrier in human blood.

5. **Conclusion**:
- Based on the evaluations, the correct answer is **Hemoglobin**.

### Final Answer:
The oxygen carrier in human blood is **Hemoglobin**.

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