Question

what does hemoglobin consists of?

Answer 1

Hemoglobin are simply iron containing protein in the blood which transport oxygen to the tissue.
Each hemoglobin molecule is made up of four heme groups which are surrounded by globin protein, heme is a part of molecule where iron atom is attached and it is this iron that binds to oxygen. There are four iron atoms in each molecule of hemoglobin which binds to four oxygen