Cell structure

Generally Prokaryotes range in size from 0.1 to 10 μm, and have one of three basic shapes: rod-like (bacilli), spherical (cocci), or helically coiled (spirilla). Like all cells, a prokaryotic cell is limited by a plasma membrane that totally encloses the cytosol and separates the cell from the external environment.  The plasma  membrane,   which  is  approximate  8  nm  thick,  consists   of  a  lipid  bilayer containing proteins. Although prokaryotes lack the membranous  subcellular  organelles  characteristic  of eukaryotes  ,their plasma membrane can be infolded to form mesosomes. The meso- somes can be the sites of deoxyribonucleic acid (DNA) replication and other specialized   enzymatic   reactions.   The mesosomes contain the proteins and pigments that trap light and generate adenosine triphosphate (ATP) in photosynthetic   bacteria. The aqueous cytosol contains the macromolecules [messenger ribonucleic acid (mRNA), enzymes transfer RNA (tRNA) and ribosomes], organic compounds   and ions required for cellular metabolism. within the cytosol is also the prokaryotic 'chromosome' consisting of a single circular molecule of DNA which is condensed to form a body called as the nucleoid.