Prokaryotic organisms are unicellular and the cells have a simple structure. They have no membrane-bound organelles and their genetic material is a single, compact loop of supercoiled DNA called a chromosome.The genes on the chromosome are often grouped into operons, a cluster of genes that are transcribed together to give a single messenger RNA (mRNA) molecule. This allows a group of proteins to be synthesised at the same time.The ribosomes are 70S ribosomes unlike the 80S ribosomes of eukaryotes.The cell walls are made of peptidoglycan (murein).The flagella are thinner, more simple structures which do not have the 9+2 structure of Eukaryotic cilia and flagella. They are made of a protein called flagellin and are attached to the cell membrane by a basal body and rotated by a molecular motor.Some bacteria have attachment structures called pili and a slime capsule for protection.