Remember, hemoglobin consists of two alpha units and two beta units. So in individuals with sickle cell anemia, the glutamic acid amino acid at position number six on the beta subunit hemoglobin is replaced by valium. And what that does is it changes the hydrophobic properties of hemoglobin. Now, that's not really a problem when the hemoglobin is bound to oxygen. But as soon as the hemoglobin unloads that oxygen in the tissues, what happens is the three dimensional shape of that hemoglobin changes as a result of that valine amino acid. And so what happens is because the red blood cells are filled with these hemoglobin molecules.