Charateristic feature of hemoglobin

Options

A. Reversible uniion with oxygen
B. Red color
C. Presence of Cu
D. Presence of Globulin protein

Answer

### Step-by-Step Solution:

1. **Understanding Hemoglobin**: Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen from the lungs to the rest of the body.

2. **Reversible Union with Oxygen**: One of the key characteristics of hemoglobin is its ability to bind reversibly with oxygen. This means that hemoglobin can pick up oxygen in the lungs and release it in the tissues where it is needed for aerobic respiration.

3. **Iron-Containing Protein**: Hemoglobin contains iron, which is crucial for its function. The iron atoms in hemoglobin bind to oxygen molecules, allowing for efficient transport.

4. **Color of Hemoglobin**: Hemoglobin gives blood its red color when it is oxygenated (bound to oxygen). This is due to the iron content, which changes color when it binds to oxygen.

5. **Function in Metabolism**: By transporting oxygen, hemoglobin plays a vital role in metabolism, as oxygen is necessary for aerobic respiration, which provides energy to cells.

6. **Other Options**: The other options provided (presence of copper and presence of globulin protein) are not characteristic features of hemoglobin. Hemoglobin does not contain copper, and while it is a protein, it is specifically classified as a globular protein due to its structure.

### Conclusion:
The characteristic feature of hemoglobin is its **reversible union with oxygen**, making the first option the correct answer.

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