Haemoglobin is a protein found in red blood cells responsible for transporting oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs. Its structure includes four globin protein chains, each associated with a heme group. At the center of each heme group is an atom of Iron (Fe). This iron atom is crucial for binding oxygen molecules. Zinc, Magnesium, and Copper are essential trace elements in the human body, involved in various enzymatic and physiological processes, but they are not the central metal in the haemoglobin molecule. For example, Magnesium is found in chlorophyll (in plants), and Zinc is involved in many enzymes.