prokaryote

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prokaryote:

see MoneraMonera,
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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Prokaryote

 

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.

REFERENCE

Peshkov, M. A. Tsitologiia bakterii. Moscow-Leningrad, 1955.

IU. I. POLIANSKII

prokaryote

[prō′kar·ē‚ōt]
(cell and molecular biology)
A primitive nucleus, where the deoxyribonucleic acid-containing region lacks a limiting membrane.
Any cell containing such a nucleus, such as the bacteria and the blue-green algae.
References in periodicals archive ?
As opposed to prokaryotic cells in which pigment molecules are attached to peripheral membranes of the cell, the chloroplast represents highly organized arrangements of the chlorophyll, and the other pigment molecules are arranged in specific double membrane layers called thylakoids.
Prokaryotic cells usually have a single, circular chromosome located in a part of the cytoplasm called the nucleoid (nuclear region).
By comparing the difference in sequences of homologous genes encoding ribosomal RNA (16S rRNA genes from prokaryotic cells and 18S rRNA from eukaryotic cells) we can measure the evolutionary distance between species of organisms.
Prokaryotic cells, which are represented by the eubacteria and archaea, contain precious little internal compartmentalization and have transcriptionally coupled translation, whereas eukaryotic cells, which compose plants, fungi, algae, animals, and a widely diverse group of unicellular protists, are equipped with a large cadre of intracellular compartments that are functionally specialized for specific intracellular tasks.
For instance, the precise 3-D localization of proteins within prokaryotic cells is key to many cellular functions, including cell cycle, DNA replication, development, motility, and adhesion.
The evolution of the origin of T-DNA in the bacterial plasmids is unknown, but it is of considerable interest because the T-DNA encodes genes that are expressed in both eukaryotic and prokaryotic cells.
Yet mechanical force can affect both eukaryotic and prokaryotic cells.
Prokaryotic cells are much smaller and simpler than eukaryotic cells.
Students know how prokaryotic cells, eukaryotic 1 or 2 ** cells (including those from plants and animals), and viruses differ in complexity and general structure.