This model of hemoglobin is 20 million times real life. Hemoglobin is responsible for carrying and delivering the oxygen in our blood. In humans, hemoglobin contains 4 subunits consisting of two alpha and two beta subunits non-covalently bound. Each subunit contains a heme group with an iron (Fe) ion capable of binding an oxygen molecule (O2). Here the atoms of each heme group are displayed, with the central Fe atom in green. This model shows hemoglobin in a deoxygenated state with one alpha (pink) and one beta (red & orange) subunit surrounded by a white ring for added structural strength. To complete the tetrameric protein, purchase two models.