The main function of the hemoglobin is to carry the oxygen molecules from the lungs to the cells present in the body of the organism and the carbon dioxide from the cell to the lungs.
The hemoglobin is a protein present in the red blood cells. it is a globular protein having heme group. The heme group helps in the binding of the oxygen to the hemoglobin and the RBCs, and is also responsible for the red coloration of the blood.