Cytosol
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{{Unreferenced|date=December 2007}}
The '''cytosol''' ([[cf.]] ''[[cytoplasm]]'', (often abbreviated ICF [intracellular fluid]) which also includes the [[organelle]]s) is the internal fluid of the [[cell (biology)|cell]], and where a portion of cell [[metabolism]] occurs. [[Protein]]s within the cytosol play an important role in [[signal transduction]] pathways and [[glycolysis]]. They also act as intracellular [[receptor (biochemistry)|receptor]]s and form part of the [[ribosome]]s, enabling protein [[Peptide synthesis|synthesis]].
In [[prokaryotes]], all chemical reactions take place in the cytosol. In [[eukaryote]]s, the cytosol surrounds the cell [[organelle]]s; this is collectively called the [[cytoplasm]]. In plants, the amount of cytosol can be reduced because of the large [[tonoplast]] (central [[vacuole]]) that takes up most of the cell interior volume. The portion of cytosol in the nucleus is called [[nucleohyaloplasm]].
The cytosol also surrounds the [[cytoskeleton]], which is made of fibrous proteins (e.g., [[microfilament]]s, [[microtubule]]s, and [[intermediate filament]]s). In many organisms, the cytoskeleton maintains the shape of the cell, anchors organelles, and controls internal movement of structures (e.g., transport [[vesicle (biology)|vesicle]]s).
The cytosol appears to be composed of free-floating particles, but is highly organized on the molecular level. As the concentration of [[soluble]] molecules increases within the cytosol, an [[osmosis|osmotic]] gradient builds up toward the outside of the cell. Water flows into the cell, making the cell bigger. To prevent the cell from bursting apart, molecular pumps in the [[plasma membrane]], the cytoskeleton, the tonoplast or the [[cell wall]] (if present), are used to counteract the [[osmotic pressure]].
Cytosol consists mostly of water, dissolved ions, small molecules, and large water-soluble molecules (such as protein). Cytosol has a high concentration of K+ ions and a low concentration of Na+ ions.
Normal human cytosolic [[pH]] is (roughly) 7.0 (i.e., neutral), whereas the [[pH]] of the [[extracellular fluid]] is 7.4.
[[Category:Cell anatomy]]
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