Haemoglobin is a:
1. Oligomeric protein 2. Chromoprotein 3. Monomeric protein 4. Keratin

Options

A. 1, 2 and 3 are correct
B. 1 and 2 are correct
C. 2 and 4 are correct
D. 1 and 3 are correct

Answer

To determine the correct classification of hemoglobin from the given options, we can analyze each option step by step.

### Step 1: Understand what hemoglobin is
Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen from the lungs to the body tissues and carrying carbon dioxide back to the lungs.

### Step 2: Analyze the options
1. **Oligomeric protein**: Oligomeric proteins are composed of multiple subunits. Hemoglobin consists of four subunits (two alpha and two beta chains), making it an oligomeric protein.

2. **Chromoprotein**: Chromoproteins are proteins that contain a pigmented prosthetic group. Hemoglobin contains heme, which is a pigmented group that binds oxygen, thus it can also be classified as a chromoprotein.

3. **Monomeric protein**: Monomeric proteins consist of a single polypeptide chain. Since hemoglobin is made up of multiple subunits, this classification is incorrect.

4. **Keratin**: Keratin is a fibrous structural protein found in hair, nails, and skin. Hemoglobin does not fit this classification, making it incorrect.

### Step 3: Conclusion
From the analysis:
- Hemoglobin is an **oligomeric protein** (Option 1 is correct).
- Hemoglobin is also a **chromoprotein** (Option 2 is correct).
- Options 3 (Monomeric protein) and 4 (Keratin) are incorrect.

Thus, the correct classifications for hemoglobin are **Option 1 (Oligomeric protein)** and **Option 2 (Chromoprotein)**.

### Final Answer
Hemoglobin is both an oligomeric protein and a chromoprotein. Therefore, the best answer from the options provided is **Option 1 and Option 2**.

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