Q. In sickle cell anemia, a hereditary disease, there is replacement of one amino acid by another in one of the four polypeptide chains of hemoglobin. In this case are all of the structural levels of the protein modified?

In sickle cell disease there is a modification in the primary protein structure of one of the polypeptide chains that form haemoglobin, the amino acid glutamic acid is substituted by the amino acid valine in the β chain. The spatial conformation of the molecule in addition is also modified and affected by this primary "mistake" and the modification also creates a different (sickle) shape to the red blood cells.

Sickled, Modified, red blood cells sometimes aggregate and obstruct the peripheral circulation causing tissue hypoxia and the pain crisis typical of sickle cell anemia.