Compare the structure of prokaryotic and eukaryotic organisms.

Prokaryotic and eukaryotic organisms have some similar structures: cells membranes (selectively permeable membranes surrounding cells and controlling the entry and exit of materials), cytoplasm (the living substance inside a cell), ribosomes (the site of protein synthesis and differen sizes in the different types of organisms) and, in some eukaryotes, cell walls (support providing structure on the outside of a cell). 

They do also have some differences, these include the fact that the genetic material of prokaryotic cells is a single loop of DNA that lies in the cytoplasm but in eukaryotic organisms, it is in the nucleus. Also, prokaryotes are smaller and have additional DNA in the form of plasmids. Plasmids are small, ringed DNA molecules and are very rarely found in eukaryotes.