Red blood cells have no nucleus; which term describes these cells?

• A. Erythrocytes
• B. Platelets
• C. Lymphocytes
• D. Monocytes

Answer: (A)

The main idea is identifying the standard name for red blood cells in humans. Mature red blood cells in humans lack a nucleus because, during their development, they eject the nucleus to make more room for hemoglobin, optimizing their job of carrying oxygen. This anucleate, biconcave cell is called an erythrocyte, with erythro- meaning red and -cyte meaning cell.

Platelets are cell fragments that also lack a nucleus but aren’t red blood cells; they’re involved in clotting. Lymphocytes and monocytes are white blood cells that do have nuclei and are part of the immune system. So the term that correctly describes red blood cells, given their lack of a nucleus, is erythrocytes.