Which cells are missing a nucleus?

Red blood cells are unique among the cell types mentioned as they lose their nucleus during maturation. This loss occurs when they are in the bone marrow, making them anucleated cells in their functional form. The absence of a nucleus allows red blood cells to maximize their capacity for hemoglobin, the protein responsible for transporting oxygen throughout the body. The lack of a nucleus also contributes to the biconcave shape of red blood cells, which increases the surface area for gas exchange and enhances their ability to navigate through small capillaries.

Muscle cells, neurons, and white blood cells, on the other hand, all retain their nuclei. Muscle cells contain several nuclei, particularly in skeletal muscle fibers, which help in the regulation of their metabolic activities. Neurons have a single prominent nucleus that is critical for the synthesis of proteins necessary for their complex functions. White blood cells also possess nuclei, which are vital for their role in immune responses, as they need to generate and regulate various proteins and signals essential for fighting infection.