stabilizing material in prokaryotes ?
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A prokaryote is a unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle.[1] The word prokaryotecomes from the Greek πρό (pro) "before" and κάρυον (karyon) "nut or kernel".[2][3]Prokaryotes are divided into two domains, Archaea and Bacteria. In contrast, species with nuclei and organelles are placed in the third domain, Eukaryota.[4]
In the prokaryotes, all the intracellular water-soluble components (proteins, DNA and metabolites) are located together in the cytoplasm enclosed by the cell membrane, rather than in separate cellular compartments. Bacteria, however, do possess protein-based bacterial microcompartments, which are thought to act as primitive organelles enclosed in protein shells.[5][6] Some prokaryotes, such as cyanobacteriamay form large colonies. Others, such as myxobacteria, have multicellular stages in their life cycles.[7]
Molecular studies have provided insight into the evolution and interrelationships of the three domains of biological species.[8] Eukaryotes are organisms, including humans, whose cells have a well defined membrane-bound nucleus (containing chromosomal DNA) and organelles. The division between prokaryotes and eukaryotes reflects the existence of two very different levels of cellular organization. Distinctive types of prokaryotes include extremophiles and methanogens;
Prokaryotic cells are much smaller than eukaryotic cells, have no nucelus, and lack organelles.
All prokaryotic cells are encased by a cell wall. Many also have a capsule or slime layer made of polysaccharide.
Prokaryotes often have appendages (protrusions) on their surface. Flagella and some pili are used for locomotion, fimbriae help the cell stick to a surface, and sex pili are used for DNA exchange.
Most prokaryotic cells have a single circular chromosome. They may also have smaller pieces of circular DNA called plasmids.