Name the metal which is an essential component of haemoglobin.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Hemoglobin**: Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen throughout the body. It consists of four subunits, each containing a heme group.

2. **Identifying the Components of Hemoglobin**: Each heme group contains a metal ion at its center. This metal ion is crucial for the function of hemoglobin, as it binds to oxygen molecules.

3. **Recognizing the Metal in Heme**: The specific metal that is part of the heme group in hemoglobin is essential for its oxygen-carrying capacity.

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