View of Human Oxygenated Hemoglobin Dimer.  Oxygenated Hemoglobin (Oxy Hb) is a quatrameric (only two are shown) oxygen binding protein found in the red blood cells of blood.  The Hb quatramer contains four heme groups, one in each monomer.  The heme groups are displayed in various views, but can also be turned on and off using the "Ligands" bottons.  Each heme group binds only one O₂, thus enabeling hemoglobin to carry four O₂.