Relationship to eukaryotes

The division to prokaryotes and eukaryotes is usually considered the most important distinction among organisms. The distinction is that eukaryotic cells have a "true" nucleus containing their DNA, whereas prokaryotic cells do not have a nucleus. The difference is that ribosomes in prokaryotes are smaller than in eukaryotes. However, two organelles found in many eukaryotic cells, mitochondria and chloroplasts, contain ribosomes similar in size and makeup to those found in prokaryotes.

The genome in a prokaryote is held within a DNA/protein complex in the cytosol called the nucleoid, which lacks a nuclear envelope. The complex contains a single, cyclic, double-stranded molecule of stable chromosomal DNA, in contrast to the multiple linear, compact, highly organized chromosomes found in eukaryotic cells.

Prokaryotes lack distinct mitochondria and chloroplasts. Instead, processes such as oxidative phosphorylation and photosynthesis take place across the prokaryotic cell membrane. Both eukaryotes and prokaryotes contain large RNA/protein structures called ribosomes, which produce protein.

Prokaryotic cells are usually much smaller than eukaryotic cells. Therefore, prokaryotes have a larger surface-area-to-volume ratio, giving them a higher metabolic rate, a higher growth rate, and, as a consequence, a shorter generation time than Eukaryotes.

Eukaryote[juːˈkæri.oʊt] is an organism whose cells contain complex structures enclosed within membranes.

Most eukaryotic cells contain membrane-bound organelles such as mitochondria, chloroplasts and the Golgi apparatus. All large complex organisms are eukaryotes, including animals, plants and fungi. The group also includes many unicellular organisms.

Cell division in eukaryotes is different from that in organisms without a nucleus (Prokaryote). Eukaryota appears to be monophyletic, and so makes up one of the three domains of life. The two other domains, Bacteria and Archaea, are prokaryotes and have none of the above features. Eukaryotes represent a tiny minority of all living things; even in a human body there are 10 times more microbes than human cells. However, due to their much larger size their collective worldwide biomass is estimated at about equal to that of prokaryotes.