Prokaryotes (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus, + suffix -otos, pl. -otes; also spelled "procaryotes") are organisms without a cell nucleus (= karyon), or indeed any other membrane-bound organelles, in most cases unicellular (in rare cases, multicellular). This set of characteristics is distinct from eukaryotes (also spelled "eucaryotes"), organisms that have cell nuclei and may be variously unicellular or multicellular. The difference between the structure of prokaryotes and eukaryotes is so great that it is considered to be the most important distinction among groups of organisms. Most prokaryotes are bacteria, and the two terms are often treated as synonyms. However, Woese has proposed dividing prokaryotes into the Bacteria and Archaea (originally Eubacteria and Archaebacteria) because of the significant genetic differences between the two. This arrangement of Eukaryota, Bacteria, and Archaea is called the three-domain system. This replaces the two-empire system.

The cell structure of prokaryotes differs greatly from eukaryotes in many ways. The defining characteristic is, of course, the absence of a nucleus or nuclear envelope. Prokaryotes also were previously considered to lack cytoskeletons and do lack membrane-bound cell compartments such as vacuoles, endoplasmic reticulum/endoplasmic reticula, mitochondria and chloroplasts. In eukaryotes, the latter two perform various metabolic processes and are believed to have been derived from endosymbiotic bacteria. In prokaryotes similar processes occur across the cell membrane; endosymbionts are extremely rare. Prokaryotes also have cell walls, while some eukaryotes, particularly animals, do not. Both eukaryotes and prokaryotes have structures called ribosomes, which produce protein. Prokaryotes are usually much smaller than eukaryotic cells.

Prokaryotes have a single circular (only exceptionally linear, as in Borrelia burgdorferi or the Streptomyces) chromosome, contained within a region called the nucleoid rather than in a membrane-bound nucleus, but may also have various small circular pieces of DNA called plasmids spread throughout the cell. Reproduction is most often asexual, through binary fission, where the chromosome is duplicated and attaches to the cell membrane, and then the cell divides in two. However, they show a variety of parasexual processes where DNA is transferred between cells, such as transformation and transduction.

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@jasonwryan was the integration of ATP-ADP cycle in your prokaryotic ancestors also #bloat?
samfarrow (Sam Farrow) Mon, 21 Dec 2009 20:36:12 -0000
@jasonwryan was the integration of ATP-ADP cycle in your prokaryotic ancestors also #bloat?
あ…大量培養していたtetrahymenaにE.coliがコンタミしている…prokaryoticな鞭毛はいらないのですのに．
yamano_twit (Takashi Yamano) Mon, 21 Dec 2009 20:14:04 -0000
あ…大量培養していたtetrahymenaにE.coliがコンタミしている…prokaryoticな鞭毛はいらないのですのに．
http://go.meebo.com/soompi.com/3FA way too hot!!
prokaryotic (normala) Mon, 21 Dec 2009 08:52:24 -0000
http://go.meebo.com/soompi.com/3FA way too hot!!
revising prokaryotic and eukaryotic cells isnt cool! *longs for the snow*
CheekyTiggerBel (The 'itty bit') Sun, 20 Dec 2009 16:40:53 -0000
revising prokaryotic and eukaryotic cells isnt cool! *longs for the snow*
Why do systematic biologist now reject the use of a single kingdom Monera for all prokaryotic organi http://bit.ly/4vsxXH
juranfudi (liki miana) Sun, 20 Dec 2009 01:20:42 -0000
Why do systematic biologist now reject the use of a single kingdom Monera for all prokaryotic organi http://bit.ly/4vsxXH
New PSORTdb includes new PSORTb precomputed results for all NCBI prokaryotic genomes so our PSORTb site hopefully doesn't get hammered. :)
fionabrinkman (Fiona Brinkman) Sat, 19 Dec 2009 04:47:55 -0000
New PSORTdb includes new PSORTb precomputed results for all NCBI prokaryotic genomes so our PSORTb site hopefully doesn't get hammered. :)

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