The cytosol, hyaloplasm, cytoplasmic matrix or intracellular fluid, is the soluble part of the cytoplasm, that is, the liquid found within eukaryotic or prokaryotic cells. The cell, as a self-contained unit of life, is defined and delimited by the plasma membrane; from this to the space occupied by the nucleus is the cytoplasm, with all its associated components.
In the case of eukaryotic cells, these components include all organelles with membranes (such as nucleus, endoplasmic reticulum, mitochondria, chloroplasts, etc.), as well as those that do not have it (such as ribosomes, for example).
All these components, together with the cytoskeleton, occupy a space inside the cell: we could say, therefore, that everything in the cytoplasm that is not a membrane, cytoskeleton or another organelle is cytosol.
This soluble fraction of the cell is fundamental for its operation, in the same way that empty space is necessary to accommodate stars and stars in the universe, or that the empty fraction of a painting allows defining the shape of the object that is drawn.
The cytosol or hyaloplasm thus allows the components of the cell to have a space to occupy, as well as the availability of water and thousands of other different molecules to carry out their functions..
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The cytosol or hyaloplasm is mainly water (about 70-75%, although it is not uncommon to observe up to 85%); however, there is so much dissolved substance in it that it behaves more like a gel than a fluid aqueous substance.
Among the molecules present in the cytosol, the most abundant are proteins and other peptides; but we also find large amounts of RNA (particularly messenger RNAs, transfer RNAs and those that participate in post-transcriptional genetic silencing mechanisms), sugars, fats, ATP, ions, salts and other cell-type specific metabolism products of which is concerned.
The structure or organization of the hyaloplasm varies not only by cell type and by conditions of the cell environment, but it can also be different according to the space it occupies within the same cell..
In any case, you can adopt, physically speaking, two conditions. As a plasma gel, hyalopasm is viscous or gelatinous; as plasma sun, on the contrary, it is more liquid.
The passage from gel to sol, and vice versa, within the cell creates currents that allow movement (cyclosis) of other unanchored internal components of the cell.
In addition, the cytosol can present some globular bodies (such as lipid droplets, for example) or fibrillar, basically constituted by components of the cytoskeleton, which is also a very dynamic structure that alternates between more rigid macromolecular conditions, and others more relaxed.
Primarily, the cytosol or hyaloplasm not only allows the organelles to be located in a context that allows their physical but also functional existence. That is, it provides them with the conditions of access to the substrates for their operation, and also, the medium in which their products will be “dissolved”..
Ribosomes, for example, obtain from the surrounding cytosol the messenger and transfer RNAs, as well as the ATP and water necessary to carry out the biological synthesis reaction that will culminate in the release of new peptides..
In addition to protein synthesis, other fundamental biochemical processes such as the universal glycolysis take place in the cytosol, as well as others of a more specific nature by cell type..
The cytosol, also, is the great regulator of intracellular pH and ionic concentration, as well as the intracellular communication medium par excellence..
It also allows a huge number of different reactions to take place, and can function as a storage site for different compounds..
The cytosol also provides a perfect environment for the functioning of the cytoskeleton, which among other things, requires extremely fluid polymerization and depolymerization reactions to be effective..
The hyaloplasm provides such an environment, as well as access to the necessary components so that such processes are verified in a fast, organized and efficient way..
On the other hand, as indicated above, the nature of the cytosol allows the generation of internal movement. If this internal movement is also responsive to signals and requirements of the cell itself and its environment, cell displacement can be generated..
That is, the cytosol allows not only the internal organelles to self-assemble, grow and disappear (if applicable), but the cell as a whole to modify its shape, move or join some surface.
Finally, the hyaloplasm is the great organizer of global intracellular responses..
It allows not only specific regulatory cascades (signal transduction) to be experienced, but also, for example, calcium surges that involve the whole cell for a wide variety of responses.
Another response that involves the orchestrated participation of all the components of the cell for its correct execution is mitotic division (and meiotic division)..
Each component must respond effectively to division signals, and do so in such a way that it does not interfere with the response of the other cellular components - particularly the nucleus..
During the processes of cell division in eukaryotic cells, the nucleus renounces its colloidal matrix (nucleoplasm) to assume that of the cytoplasm as its own..
The cytoplasm must recognize as its own component a macromolecular assembly that was not there before and that thanks to its action must now be precisely distributed between two new derived cells.
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