A cell is a prokaryote because b. it lacks a cell membrane. As a result, a prokaryote does not have an organized nucleus. The DNA is clumped together inside the cell. An eukaryote, on the other hand, is a cell with a cell membrane around the nucleus. It's amazing to realize that a cell can function without an organized nucleus. Most prokaryote's are bacteria and they exist everywhere on our planet. They are also very simple organisms - the simplest organisms on our planet.