And we also have beta one and beta two subunit. Now, each of these subunits contains a hein group shown in brown. And that heme group is capable of binding a single diatomic oxygen molecule. So once our two three BPG molecule enters the red blood cells, what exactly takes place? Well, basically, some of these hemoglobin molecules inside our red blood cells, some of these hemoglobin proteins will not contain any oxygen and these are called deoxy hemoglobin proteins. And the two three BPG molecules, these molecules will be able to bind to a cavity to a space found between the beta one and the beta two subunits of deoxyhemoglobin.