Some cells are specialised to perform specific functions. For example, mature Red Blood Cells (RBCs) in humans do not have a nucleus (enucleate). The absence of a nucleus provides more space for haemoglobin, allowing it to transport a larger amount of oxygen to all cells of the body. Since they lack a nucleus, they cannot repair or divide themselves. As a result, their lifespan is short and they survive approximately for 120 days. Do you know any other cells without nucleus?
[Pg. No. 16]

Yes. Apart from mature human RBCs, some other cells or cell-like structures without a true nucleus are:

(1) Sieve tube cells in plants: Mature sieve tube elements of phloem do not have a nucleus. They remain living but depend on nearby companion cells for their control and functioning.

(2) Mature xylem vessels and tracheids: These cells lose their nucleus and cytoplasm at maturity. They become dead, hollow tubes that help in the transport of water and minerals in plants.

(3) Platelets in human blood: Platelets do not have a nucleus, but they are not complete cells. They are small cell fragments that help in blood clotting.