cytosoli

Cytosoli, commonly referred to as the cytosol, is the intracellular fluid portion of the cytoplasm in cells. It is the aqueous, gel-like medium in which organelles float and metabolic processes take place. The cytosol is distinct from organelles and membranes, and in many contexts the term cytoplasm is used to denote cytosol together with the organelles it contains.

Composition and properties

The cytosoli is predominantly water but contains a wide mixture of dissolved ions, small molecules, metabolites, and a high concentration of soluble proteins, enzymes, and ribosomes. The ionic environment typically features potassium and magnesium ions, among others, with a pH near neutral. The cytosol is highly crowded with macromolecules, which influences reaction rates and diffusion. It also hosts the cytoskeletal network, composed of actin filaments, microtubules, and intermediate filaments, that provides structure and facilitates movement within the cell.

Functions and organization

The cytosoli is the site of numerous metabolic pathways, including glycolysis, and supports protein folding, turnover, and various signaling processes. It acts as a conduit for the distribution of metabolites, ions, and energy carriers, and serves as a medium where free ribosomes translate mRNA into proteins. The cytosol is dynamic and responsive to cellular states such as growth, stress, and differentiation.

Membraneless organization

In recent years, the concept of membraneless organelles—biomolecular condensates such as stress granules and P bodies—has highlighted the functional compartmentalization within the cytosoli. These structures concentrate specific proteins and RNAs to regulate particular biochemical reactions.

Notes

Cytosoli is the term used in some languages to denote the cytosol. In many contexts, cytosol and cytoplasm are distinguished by the inclusion or exclusion of membranes and organelles.