A cytosol is a semi-liquid cytoplasmic fraction that fills the space between the internal structural components of a cell. In cytology, the term hyaloplasm is used as a synonymous concept. The cytosol is morphologically unstructured and plays the role of a cytoplasmic matrix in which formed cellular elements (eukaryotic organelles, prokaryotic compartments, inclusions) are located.
Definition of a concept
In a general sense, a cytosol is a cytoplasm without its structural components, which are different in prokaryotes and eukaryotes. Therefore, for bacteria, this definition will mean "without ribosomes, inclusions and membrane formations." The cytosol in a eukaryotic cell is the cytoplasm from which organelles and inclusions were excluded.
The term was first introduced in 1965 to refer to the fluid remaining after ultracentrifugation of a damaged cytological mass. The word is formed by combining the Greek "cell" and the English "solution". Indeed, in the biochemical sense, cytosol is an aqueous solution of various organic substances (proteins, polysaccharides, RNA, etc.) and inorganic nature.
Liquids contained inside organelles are not part of hyaloplasm.
General characteristics and composition
In electron micrographs, the cytosol is a filling interstructural space of a cell, homogeneous or fine-grained matter with a low electron density. It is noteworthy that hyaloplasm is able to change its state of aggregation from a liquid to a gel-like state and vice versa.
Chemically, cytosol is a complex colloidal system containing many substances, including:
- transport RNA;
- enzymes;
- structural proteins;
- organic acids;
- nucleotides;
- carbohydrates;
- ATP and other macroergic compounds;
- ions (calcium, potassium, sodium, magnesium, etc.).
In other words, hyaloplasm is a receptacle for a whole set of biological molecules, as well as a real biochemical station, which combines all cellular structures and determines their interaction with each other. In the cytosol, many metabolic reactions occur.
About 70% of the chemical composition of hyaloplasm is in water, 20% in proteins, and only 10% in other chemical components. This structureless substance occupies up to 55% of the internal volume of the cell. Numerous functions of the cytosol are associated with the fact that, like blood in the body, it is a binding substance for all components of the cytoplasm.
Protein molecules contained in the hyaloplasm can form various fibrillar or filamentous complexes.
Cell Cytosol Functions
Being an intracellular medium, the cytosol performs many functions, which include:
- transport - hyaloplasm is the space through which various cellular components (molecules, ions, ribosomes, etc.) move;
- biochemical - many chemical reactions take place in the cytosol;
- osmotic - the concentration of ions in the hyaloplasm provides the osmotic properties of the cell;
- turgor - the pressure of the hyaloplasm on the walls of the cell membrane ensures its elasticity;
- supporting - hyaloplasm plays the role of a structural matrix in which cellular components are placed in a certain way;
- communication - cytosol can serve as a medium for the transmission of intracellular signals;
- distribution (typical for cells with an uneven distribution of some components throughout the cytoplasm).
Since the bulk of the cytosol is water, it also acts as a solvent for organic molecules and ions.