The domain containing all organisms with eukaryotic cells is the Domain Eukarya. There are only three domains; the Archaea, Bacteria and Eukarya. Domain Eukarya came from the first prokaryotic cells billions of years ago. In the cytoplasm, ribsomal RNA (rRNA), a type of RNA, and protein combine to form a nucleoprotein called a ribosome. The ribosome serves as the site and carries the enzymes necessary for protein synthesis. They are often takes the shape of small round particles attached in the endoplasmic reticulum. The ribosome attaches itself to m-RNA and provides the stabilizing structure to hold all substances in position as the protein is synthesized. Several ribosomes may be attached to a single RNA at any time
