Which of the following is a chromoprotein?

Options

A. Keratin
B. Casein
C. Haemoglobin
D. Ferritin

Answer

To determine which of the following is a chromoprotein, we need to understand what a chromoprotein is.

### Step-by-Step Solution:

1. **Definition of Chromoprotein**:
- A chromoprotein is a type of conjugated protein that contains a pigmented prosthetic group. This means it is a protein that has a non-protein component (the prosthetic group) that is colored and contributes to the protein's overall color.

2. **Understanding Prosthetic Groups**:
- The prosthetic group in a chromoprotein is typically a non-protein molecule that is responsible for the pigmentation. This group can be a metal ion or a pigment that gives the protein its color.

3. **Analyzing the Options**:
- **Option A: Keratin**:
- Keratin is a structural protein found in hair and nails. It does not have a pigmented prosthetic group and does not produce color, so it is not a chromoprotein.
- **Option B: Casein**:
- Casein is a milk protein that is white in color. It does not contain a pigmented prosthetic group, hence it is also not a chromoprotein.
- **Option C: Hemoglobin**:
- Hemoglobin is found in red blood cells and is responsible for transporting oxygen. It contains heme as a prosthetic group, which is pigmented and gives hemoglobin its red color. Therefore, hemoglobin is a chromoprotein.
- **Option D: Ferritin**:
- Ferritin is a protein that stores iron and does not have a pigmented prosthetic group. It is primarily a storage protein and not a chromoprotein.

4. **Conclusion**:
- Based on the analysis, the correct answer is **Option C: Hemoglobin**, as it is the only protein listed that qualifies as a chromoprotein due to its pigmented prosthetic group.

### Final Answer:
**Hemoglobin (Option C) is a chromoprotein.**

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