Final answer:
RBCs lose their nucleus during their developmental process in the red bone marrow to allow for a greater concentration of hemoglobin, optimizing their ability to deliver oxygen to the body's tissues. This process results in mature RBCs without a nucleus, leading to their characteristic biconcave shape and increased efficiency in oxygen transportation.
Step-by-step explanation:
Red blood cells (RBCs), also known as erythrocytes, lose their nucleus during their maturation process to become mature RBCs. This event occurs in the red bone marrow during the erythrocyte development process. In mammals, the immature RBCs, known as erythroblasts, expel their nucleus to make room for a higher concentration of hemoglobin, the protein that carries oxygen. Without a nucleus, RBCs become more efficient at transporting oxygen throughout the body.
The ejection of the nucleus occurs after the erythroblast has passed through several developmental stages. Once the nucleus is expelled, the erythrocyte loses the ability to produce proteins and to divide, thus becoming a mature RBC. This specialization allows the cell to be biconcave, increasing its surface area and flexibility, which is essential for its capacity to efficiently carry oxygen through the small capillaries to tissues. Consequently, the lack of organelles, including the nucleus, gives the RBC its characteristic donut shape and enhances its oxygen-carrying capacity.
Mature red blood cells lack organelles such as a nucleus, endoplasmic reticulum, and mitochondria. This absence enables the cell to store a larger amount of hemoglobin. The unique structure of RBCs plays a critical role in their principal job, which is to carry and deliver oxygen to the tissues. Because they lack a nucleus, RBCs cannot repair themselves, leading to a lifespan of about 120 days. After this period, they are typically phagocytized and recycled by the spleen and liver.
Comparatively, white blood cells (WBCs), which are involved in the immune response to defend against pathogens, retain their nucleus throughout their life. In contrast to red blood cells, white blood cells have a nucleus and play no role in oxygen transport.