If blood cells don't have a nucleus and don't reproduce, how do we get more blood? What happens to the dead blood cells?

Red blood cells are considered cells, but they lack a nucleus, DNA, and organelles like the endoplasmic reticulum or mitochondria. Red blood cells cannot divide or replicate like other bodily cells. They cannot independently synthesize proteins,The nucleus is the cell's brain which controls much of its functions. An animal cell or eukaryotic cell will therefore die without a nucleus. The cell would not know what to do without a nucleus and there would be no cell division. The synthesis of proteins will either stop or shape wrong proteins.When red cells die, hemoglobin is broken up: iron is salvaged, transported to the bone marrow by proteins called transferrins, and used again in the production of new red blood cells

Explanation:

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.