PROKARYOTIC AND EUKARYOTIC CELL

 Biologists have divided cells into two types. Prokaryotic and eukaryotic. The difference between these two types of cells are mainly based upon the structure of their nuclei. Eukaryotic have a very well defined nucleus,

in which nuclear material (chromosomes or DNA) is enclosed in double nuclear membrane. In prokaryotic cells, however the genetic material (DNA) is without any nuclear membrane covering and is directly submerged in the cytoplasm. Organisms possessing prokaryotic cells are called prokaryotes and those possessing eukaryotic cells are called eukaryotes. Prokaryotes include bacteria and blue green algae. Eukaryotes include all other unicellular or multicellular organism such as animals, plants, fungi and protista.

         Prokaryotic cells generally lack many of membrane bounded structure found in eukaryotic cells. For example, mitochondria, endoplasmic reticulum, chloroplasts and Golgi apparatus are absent in prokaryotic cell. Since there is no nuclear membrane, a prokaryotic cell has no distinct nucleus and its DNA molecule is directly suspend in cytoplasm. Prokaryotes have small sized ribosomes 70S compared to eukaryotes 80S . In prokaryotes mitosis is missing and the cell divides by binary fission. Because of their simpler structure, it was widely accepted for a long time that prokaryotic cell represent a more primitive stage of evolution than eukaryotic cells. Perhaps the most distinctive feature of the prokaryotic cell is it cell wall, composed of polysaccharide chains bound covalently to shorter chains of amino acids forming peptidoglycan or murein. The entire cell wall is often regarded as a single huge molecule or molecular complex called sacculus. The cell wall of plants is generally made up of cellulose and is
differently structured than that of a bacterium.

 The prokaryotic and eukaryotic cells are simply defined as.

Prokaryotic cell.A cell that lacks a membrane bound nucleus and a cytoskeleton. All prokaryotes, including bacteria and cynobacteria, are single called-organism.

Eukaryotic cell. A cell that do not lacks a membrane bound nucleus and cytoskeleton