The Structural Organization of Cells. The cell is the smallest matter that still absorbs the characteristics of life. All cells have three basic parts, a plasma membrane splits each cell from the environment, permits the flow of molecules across the membrane, and consist receptors that can affect the cell’s activities. A DNA-containing region occupies a portion of the interior. The cytoplasm contains membrane-bound compartments (except bacteria), particles, and filaments & end ash; all bathed in a semifluid substance. Eukaryotic cells are defined by their possession of a membrane-bound nucleus. Prokaryotic cells have no defined nucleus; the only representatives are bacteria.