Final answer:
In sickle cell anemia, the abnormal component that causes erythrocytes to sickle is hemoglobin S, an abnormal type of hemoglobin resulting from a genetic mutation.
Step-by-step explanation:
In sickle cell anemia, the component that is abnormal and causes the erythrocytes (red blood cells) to change shape is a type of hemoglobin known as hemoglobin S. This is due to a genetic mutation that leads to the production of this abnormal hemoglobin. The presence of hemoglobin S causes the red blood cells to assume a sickle or crescent shape, particularly under low oxygen concentrations. This abnormal shape impedes their ability to navigate through the narrow capillaries, resulting in blockage of blood flow to various tissues and causing a range of complications, from painful joints to more severe conditions like strokes and blindness.