In humans, a condition we call sickle cell anemia afflicts red blood cells and more specifically, the hemoglobin molecules found inside red blood cells. So in individuals who have sickle cell anemia the hemoglobin molecules are slightly abnormal and we'll see exactly what that abnormality is in just a moment. Now, as a result of this abnormality in the hemoglobin globin molecule, when the hemoglobin molecule is in its deoxygenated state the hemoglobin molecules will begin to bind to one another and aggregate and eventually they'll form these long fibers in the shape of a sickle. And as a result of the formation of these fibers inside red blood cells the healthy biconcave shape of the red blood cells will transform into this abnormal sickle shape. Now, what exactly will that do? Well, let's take a look at the following diagram.