Linus Pauling--Molecular Diseases, Sickle Cell Anemia

Sickle cell anemia is a serious condition in which the red blood cells can become sickle-shaped (that is, shaped like a "C").

Normal red blood cells are smooth and round like a doughnut without a hole. They move easily through blood vessels to carry oxygen to all parts of the body. Sickle-shaped cells don't move easily through blood. They're stiff and sticky and tend to form clumps and get stuck in blood vessels.

The clumps of sickle cells block blood flow in the blood vessels that lead to the limbs and organs. Blocked blood vessels can cause pain, serious infections, and organ damage. http://www.nhlbi.nih.gov/health/dci/D.