The nucleus is the most obvious organelle in a eukaryotic cell. Virtually all eukaryote cells have a nucleus (red blood cells lose theirs and so are enucleate for most of their life-span of 180 days). It is surrounded by the nuclear envelope, a double membrane with contains a large number of pores. Molecules enter and leave the nucleus by these pores. The two lipid bilayers of the double membrane are separated by a gap of 20 to 40 nm, called the perinuclear space.
The nucleus contains the cell's DNA. …
