prokaryote

—prokaryotic /proh kar'ee ot"ik/, adj.

/proh kar"ee oht', -ee euht/, n.

any cellular organism that has no nuclear membrane, no organelles in the cytoplasm except ribosomes, and has its genetic material in the form of single continuous strands forming coils or loops, characteristic of all organisms in the kingdom Monera, as the bacteria and blue-green algae.

Also, procaryote. Cf. eukaryote.

[taken as sing. of NL Prokaryota, earlier Procaryotes (1925); see PRO-¹, EUKARYOTE]

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Any cellular organism that lacks a distinct nucleus.

Bacteria (including blue-green algae, or cyanobacteria) are prokaryotes; all other organisms are eukaryotes. Prokaryotic cells lack a nuclear membrane and most of the components of eukaryotic cells. The cytoplasm includes ribosomes that carry out protein synthesis and a double-stranded DNA chromosome, usually circular. Many prokaryotes also contain additional circular DNA molecules called plasmids. The flagella are distinct from those of eukaryotes in design and movement.

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▪ cell

also spelled  procaryote  

 any organism that lacks a distinct nucleus and other organelles due to the absence of internal membranes. Bacteria are among the best-known prokaryotic organisms. The lack of internal membranes in prokaryotes distinguishes them from eukaryotes (eukaryote). The prokaryotic cell membrane is made up of phospholipids and constitutes the cell's primary osmotic barrier. The cytoplasm contains ribosomes, which carry out protein synthesis, and a double-stranded deoxyribonucleic acid (DNA) chromosome, which is usually circular. Many prokaryotes also contain additional circular DNA molecules called plasmids (plasmid), with additional dispensable cell functions, such as encoding proteins to inactivate antibiotics. Some prokaryotes have flagella (flagellum). Prokaryotic flagella are distinct in design and movement from the flagella found on some eukaryotes. See also eukaryote; bacteria.

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