Cell–cell recognition in the context of Cellular biology

The glycocalyx is a microscopic, hair-like coating which covers the outer surface of virtually all cells, and plays a critical role in most signalling between cells and their surrounding environments. It is composed of branching biomolecules like proteins and lipids sometimes longer than the cell's own diameter, with various sugars covalently bound to them at particular locations.

The glycocalyx (pl.: glycocalyces or glycocalyxes), also known as the pericellular matrix and cell coat, is an external organelle consisting of a layer of glycosylated biomolecules called glycoconjugates, such as glycoproteins and glycolipids. These are embedded in and extend outwards from the cell membranes of virtually all cells. Generally, the carbohydrate portion of the glycolipids found on the surface of plasma membranes helps these molecules contribute to cell–cell recognition, communication, and intercellular adhesion.

In molecular biology and biochemistry, glycoconjugates are a subfamily for carbohydrates where saccharides are covalently linked with proteins, peptides, lipids. Glycoconjugates are formed in processes termed glycosylation. Glycoconjugates are involved in cell–cell interactions, including cell–cell recognition; in cell–matrix interactions; and in detoxification processes.

Although the important molecular species DNA, RNA, ATP, cAMP, cGMP, NADH, NADPH, and coenzyme A all contain a carbohydrate part, generally they are not considered as glycoconjugates.

An oligosaccharide (/ˌɒlɪɡoʊˈsækəˌraɪd/; from Ancient Greek ὀλίγος (olígos) 'few' and σάκχαρ (sákkhar) 'sugar') is a saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars). Oligosaccharides can have many functions including cell recognition and cell adhesion.

They are normally present as glycans: oligosaccharide chains are linked to lipids or to compatible amino acid side chains in proteins, by N- or O-glycosidic bonds. N-Linked oligosaccharides are always pentasaccharides attached to asparagine via a beta linkage to the amine nitrogen of the side chain. Alternately, O-linked oligosaccharides are generally attached to threonine or serine on the alcohol group of the side chain. Not all natural oligosaccharides occur as components of glycoproteins or glycolipids. Some, such as the raffinose series, occur as storage or transport carbohydrates in plants. Others, such as maltodextrins or cellodextrins, result from the microbial breakdown of larger polysaccharides such as starch or cellulose.