Oxygen is transproted in blood mainly by

Options

A. leucocytes
B. erthrocytes
C. serum
D. blood plasma

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the main component responsible for transporting oxygen in the blood.

2. **Identifying the Options**: The options given are leukocytes (white blood cells), erythrocytes (red blood cells), serum, and blood plasma.

3. **Analyzing Each Option**:
- **Leukocytes**: These are primarily involved in the immune response and do not play a significant role in oxygen transport.
- **Erythrocytes**: These are red blood cells, which are specifically designed to carry oxygen throughout the body.
- **Serum**: This is the liquid that separates from clotted blood and does not contain cells; it is not involved in oxygen transport.
- **Blood Plasma**: This is the liquid component of blood that carries cells and proteins but is not the primary means of oxygen transport.

4. **Understanding the Role of Hemoglobin**: Hemoglobin, a protein found in erythrocytes, binds to oxygen. Each hemoglobin molecule can carry up to four oxygen molecules due to its structure, which consists of four subunits, each containing a heme group that binds iron.

5. **Conclusion**: Given that hemoglobin is found in erythrocytes and is responsible for the transport of oxygen, the correct answer is **erythrocytes (red blood cells)**.

**Final Answer**: Oxygen is transported in blood mainly by **erythrocytes (red blood cells)**.

---