Sytosoli

Sytosoli, commonly spelled cytosol in many languages, refers to the intracellular fluid portion of the cytoplasm. It is the aqueous, gel-like phase that lies between the plasma membrane and the organelles and is distinct from the nuclear compartment. In prokaryotes, the cytosol constitutes the entire interior of the cell, while in eukaryotes it lies outside organelles and membranes, forming the main medium in which many cellular processes occur.

Composition and properties: The cytosol is predominantly water, but it also contains ions, small metabolites, soluble enzymes, and a variety of dissolved macromolecules such as enzymes, substrates, and signaling molecules. It is a crowded, highly organized environment with macromolecular crowding influencing reaction rates and diffusion. The pH and ionic strength of the cytosol are tightly regulated to support metabolic activities.

Functions: A wide range of metabolic pathways take place in the cytosol, including glycolysis in many cells and portions of other catabolic and anabolic processes. It hosts the cytosolic ribosomes responsible for synthesizing a subset of proteins. The cytosol also participates in signal transduction, transport of metabolites, and maintenance of cellular structure through the cytoskeleton, which is embedded within the cytosolic milieu.

Relation to other compartments: The cytosol is contained within the cell membrane and is distinct from the cytoplasm, which also encompasses organelles and inclusions. The nucleus, mitochondria, endoplasmic reticulum, and other organelles reside outside the cytosolic fluid while interacting with it through membranes and transport processes.

Clinical and research relevance: Alterations in cytosolic composition, viscosity, or enzyme activity can affect cellular metabolism and signaling, contributing to various diseases or cellular stress responses.