prokaryote(redirected from Prokaryotic cells)
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taxonomic kingdom that comprises the prokaryotes (bacteria and cyanobacteria). Prokaryotes are single-celled organisms that lack a membrane-bound nucleus and usually lack membrane-bound organelles (mitochondria, chloroplasts; see cell, in biology).
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an organism that does not have a typical cell nucleus and chromosomal apparatus. Prokaryotes include bacteria, blue-green algae, rickettsiae, and mycoplasms.
In the organic world, according to the latest classification system, prokaryotes are classified as a kingdom (Prokariota) or a superkingdom that is comparable to the kingdom or super-kingdom of eukaryotes. In prokaryotes, the physical substrate associated with the transmission and realization of hereditary information consists of a strand of deoxyribonucleic acid (DNA). The DNA usually has a ringlike shape and is localized more or less in the central part of the organism, which is called the nucleoid; the nucleoid is not separated by a membrane from the cytoplasm. Unlike the DNA in eukaryotes, the DNA in prokaryotes is usually not bound to histones (it does not form nucleohistone) and the functioning of genes is regulated through metabolites. Also, prokaryotes do not have mitochondria and complexly organized flagella.
Prokaryotes play a very important role in the cycle of matter in the biosphere. Blue-green algae were probably the first autotrophic organisms to appear on earth in the course of the evolution of life.
REFERENCEPeshkov, M. A. Tsitologiia bakterii. Moscow-Leningrad, 1955.
IU. I. POLIANSKII