Ask a Teacher

Search



WHAT IS ENDOCYTOSIS
Endocytosis is a process where cells ingest material (macromolecules, low-molecular weight molecules, and particles) from outside the cell by enclosing it with a portion of their cell membrane and bringing it into the cell in a membrane-bound vesicle. In other words, a small portion of the cell membrane (plasma membrane) invaginates and progressively encloses the extracellular substance, and then pinches off inside the cell to form a membrane-bound, intracellular vesicle with the ingested material.The function of endocytosis is the opposite of exocytosis, in which materials packaged in secretory vesicles inside the cell fuse with the plasma membrane and open to the exterior space, releasing the material.

Endocytosis is used by cells because most substances important to them are large polar molecules, and thus cannot pass through the hydrophobic plasma membrane. The material tends to remain sequestered in vesicles and does not mix with other macromolecules or organelles in the cytoplasm, other than specific membranes for which it is destined, causing a directed transfer between the inside and outside of the cell (Alberts et al. 1989). Typically, the internalized molecules trapped in the intracellular vesicles eventually fuse with the membrane-bound lysosomes and are degraded (Khalil et al. 2006).

Endocytosis may involve the ingestion of fluid and solutes or the ingestion of large particles (such as microorganisms and cell debris). The mechanism of internalizing macromolecules into cells is an intricately coordinated process. Through understanding the various endocytic uptake pathways, mechanisms can be improved for successful non-viral delivery of therapeutic genes to the particular target cells, such as necessary for gene therapy.


comments powered by Disqus