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Subject - cell biology
The cell (lat. cella "chamber") is the smallest unit that displays the characteristics of life, which include growth, reproduction, and metabolism, as well as mechanisms for self-monitoring and self-regulation.
There are two basic forms of cell: prokaryotic and eukaryotic. Organisms made of prokaryotic cells are called prokaryotes. These include bacteria and archaea. Organisms with a more developed structure are made of eukaryotic cells and are called eukaryotes. Eukaryotic cells include those in plants, animals, and fungi.
Eukaryotic cells are enclosed by a semipermeable cell membrane, which allows for material exchange with the environment. Plant cells are additionally surrounded by a rigid, cellulose-containing cell wall. In contrast, the cell walls of fungi are made of . Eukaryotes have a nucleus, whose contents include chromosomes, carriers of genetic information. Further basic organelles located in the cytoplasm include mitochondria, which are responsible for cellular respiration and energy production; the endoplasmic reticulum, which contains the ribosomes where protein synthesis occurs; and the Golgi apparatus, whose tasks include the regulation of substance transport. Animal cells contain lysosomes that contain hydrolytic enzymes (German learning unit) and are responsible for the digestion of materials from inside and outside the cell. In plant cells, this function is carried out by vacuoles, which are also responsible for the storage of organic molecules, inorganic ions, and harmful metabolic products as well as the build up of pressure within the cell (turgor). In addition to chromoplasts and leucoplasts, green plant cells also contain chloroplasts, which carry out photosynthesis.
Prokaryotic cells do not have a nucleus or most of the other organelles.
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Cytology is introduced by means of illustrations, animations, and a comprehensive collection of references and selected links.