Prokaryotic and eukaryotic cells compared

In this essay I will describe the structure of a prokaryotic cell and contrast it with the structure of an eukaryotic one. The prokaryotic cell is quite simply built, and therefore I would like not only to mention its parts - called organelles - but also to discuss some of their general functions. I would start with the major property: size. Prokaryotes are very small - 0.3 µm (Mycoplasma) up to 10 µm (Spirochete). Bigger, but still not visible for the human eye, are most eukaryotes: 5 µm (animal cell) up to 100 µm (euglena). And I say most, because there are some exceptions, like the eukaryotic egg (yolk) cell, which complained with any other cell looks absolutely huge. Both eukaryotic and prokaryotic cells are covered with permeable cell wall that protects the cell and maintains its shape; animal cells, which are eukaryotes, lack it, and that is why they are spherically shaped.