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noun, plural: cytosols

(cell biology) The liquid component of the cytoplasm surrounding the organelles and other insoluble cytoplasmic structures in an intact cell where a wide variety of cell processes take place


The cytosol is the aqueous portion of the cytoplasm in an intact cell consisting of water, organic molecules and dissolved ions. The highest percentage of cytosol component is water, i.e. about 70%. The typical ions in the mammalian cytosol are potassium, sodium, chloride, bicarbonate, amino acids in proteins, magnesium, and calcium. The concentration of potassium ions is greater in cytosol than that in the extracellular fluid. Macromolecules dissolved in the cytosol include protein molecules not bound to the cell membrane or the cytoskeleton.

The cytosol serves as the site where many chemical reactions take place. In prokaryotes, it is where most metabolic reactions take place (others occur in the cell membrane). In eukaryotes, it is where the organelles and other cytoplasmic structures are suspended. Since the cytosol contains dissolved ions, it plays a role in osmoregulation and cell signaling. It is also involved in generating action potentials such as in endocrine, nerve and muscle cells.

Word origin: cyto- (cell) + sol(ution)


  • hyaloplasm
  • cytoplasmic matrix

See also:

Related form(s):

  • cytosolic (adjective, of, or relating to, cytosol)