Do All Cells Have A Nucleus?

The vast majority of animal and plant cells all have a nucleus. The nucleus contains the DNA of the cell and this is vital for cell division and also for making the proteins that the cell needs to function.

There are always exceptions to every rule though and there are types of animal and plant cell that have no nucleus. The best known example of an animal cell is the red blood cell. Progenitor cells, cells that give rise to red blood cells all have nuclei but the mature red blood cell loses its nuclei. The cell transport oxygen and carbon dioxide around the body but all the proteins it needs to do this are in its cytoplasm and they are enzymes. This means they don't get used up in the reactions they participate in, so can be reused again and again. The cell can therefore do without protein synthesis and, as it doesn't divide, it needs no nucleus. It can't keep going forever though, and red blood cells live for about 120 days before they are replaced.

In the plant, the cells of the xylem, the tubes that run up and down the cell and are used to carry water from the roots to the leaves also lose their nucleus when they mature.

All eukaryote cells have a nucleus (eukaryotes are basically everything except bacteria and archaea). Confusion sometimes occurs with red blood 'cells' which don't have a nucleus but are corpuscles rather than cells.

Not all cell, the red blood cell does not have a nucleus to make more room for oxygen