Edit page | Page history | Printable version

Definition

noun, plural: exocytoses

The process in which the cell releases materials to the outside by discharging them as membrane-bounded vesicles passing through the cell membrane.

Supplement

The materials excreted by a cell could be a waste product or function as a regulatory molecule.

The five general steps involved in exocytosis are:
Vesicle trafficking - involves steps required to translocate the vesicle containing the material over a significant distance.
Vesicle tethering - tethering involves links over distances of more than about half the diameter of a vesicle from a given membrane surface (>25 nm).
Vesiscle docking - refers to the holding of two membranes within a bilayer's distance of one another (<5-10 nm).
Vesicle priming - include all of the molecular rearrangements and ATP-dependent protein and lipid modifications that take place after initial docking.
Vesicle fusion - driven by SNARE proteins, this is the process of merging the vesicle membrane with the target one resulting in release of large biomolecules in the extracellular space.

Word origin: exo: Gk, comb. form of éxō outside + cyte: G. kutos, hollow vessel + -osis: expressing state or condition.
Related forms: exocytose (verb), exocytotic (adjective).
Related phrases: regulated exocytosis, neuronal exocytosis.

Compare: endocytosis.
See also: plasma membrane.