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Organelles (literally "little organs") are usually membrane-bound structures inside the cell that have specific functions. Some major organelles that are suspended in the cytosol are the mitochondria, the endoplasmic reticulum, the Golgi apparatus, vacuoles, lysosomes, and in plant cells, chloroplasts.
In the 1830s, Félix Dujardin refuted Ehrenberg theory which said that microorganisms have the same organs of multicellular animals, only minor. [ 4 ] Credited as the first [ 5 ] [ 6 ] [ 7 ] to use a diminutive of organ (i.e., little organ) for cellular structures was German zoologist Karl August Möbius (1884), who used the term organula ...
Some cells, most notably Amoeba, have contractile vacuoles, which can pump water out of the cell if there is too much water. The vacuoles of plant cells and fungal cells are usually larger than those of animal cells. Vacuoles of plant cells are surrounded by a membrane which transports ions against concentration gradients.
In protists, [a] vacuoles have the additional function of storing food which has been absorbed by the organism and assisting in the digestive and waste management process for the cell. [14] In animal cells, vacuoles perform mostly subordinate roles, assisting in larger processes of exocytosis and endocytosis.
[16] while mouse cell cytosolic pH ranges between 7.0 and 7.4, and is usually higher if a cell is growing. [17] The viscosity of cytoplasm is roughly the same as pure water, although diffusion of small molecules through this liquid is about fourfold slower than in pure water, due mostly to collisions with the large numbers of macromolecules in ...
By scientific convention, the term lysosome is applied to these vesicular organelles only in animals, and the term vacuole is applied to those in plants, fungi and algae (some animal cells also have vacuoles). Discoveries in plant cells since the 1970s started to challenge this definition. Plant vacuoles are found to be much more diverse in ...
Pigments that color the cell are sometime located in the cell sap. Vacuoles can also increase the size of the cell, which elongates as water is added, and they control the turgor pressure (the osmotic pressure that keeps the cell wall from caving in). Like lysosomes of animal cells, vacuoles have an acidic pH and contain hydrolytic enzymes.
The diameter of the vacuole can occupy around 80% of the cell's diameter. [11] Thus for a 1 mm diameter cell, the vacuole can have a diameter of 0.8 mm, leaving only a path width of about 0.1 mm around the vacuole for cytoplasm to flow. The cytoplasm flows at a rate of 100 microns/sec, the fastest of all known cytoplasmic streaming phenomena. [8]