Sickle cell anemia results from the substitution of a valine for glutamic acid. Why is this medically significant? Substitution alters primary structure and function of hemoglobin resulting in decrease oxygen transport Substitution effects the quarternary structure of hemoglobin resulting in decrease oxygen transport Amino acid substitutions destroy tertiary struture of the insulin, thus increasing oxygen transport Amino acid substitution increases the transport of oxygen, but decreases the tranport of carbon dioxide..