Name the central metal ion present in haemoglobin and vitamin`B_12`?.

Explanation

To answer the question regarding the central metal ions present in hemoglobin and vitamin B12, we can break down the solution into the following steps:

### Step 1: Identify the central metal ion in hemoglobin
- Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen throughout the body. The central metal ion in hemoglobin is **iron (Fe)**.

### Step 2: Identify the central metal ion in vitamin B12
- Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a crucial role in DNA synthesis and red blood cell formation. The central metal ion in vitamin B12 is **cobalt (Co)**.

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