Glykokalvon

Glykokalvon, commonly called glycocalyx in English, is a carbohydrate-rich layer that covers the exterior of many cells. The term comes from Greek, with glyco- meaning sugar and calyx meaning husk or cover.

In bacteria, the glycocalyx is often referred to as a capsule or slime layer and consists of polysaccharides, with sometimes proteins, that the cell secretes to form a protective and adhesive coat. In most animal and plant cells, the glycocalyx is the outermost part of the plasma membrane, a sticky layer composed mainly of glycoproteins, glycolipids, and proteoglycans.

Functions include protection against mechanical stress and desiccation, regulation of hydration and ion balance, and facilitation of cell–cell and cell–surface interactions. It also plays a role in immune recognition, acts as a barrier to invading particles, and in endothelial cells contributes to vascular permeability and shear stress sensing. The glycocalyx can influence how cells interact with their environment and with other cells, and its composition is relevant to development and tissue organization.

Clinical and research relevance: In bacteria, the capsule can enhance virulence by inhibiting phagocytosis. In humans, alterations of the glycocalyx are associated with inflammation, diabetes-related microvascular complications, and cancer progression through effects on adhesion and signaling. Its integrity is important for normal physiology, while disruption can contribute to disease processes.

Study and visualization: Capsules can be seen with special stains such as India ink in bacteria; the glycocalyx is analyzed with lectin binding assays, immunostaining, and electron microscopy. Its composition and thickness vary by cell type and environment, reflecting dynamic regulation of this extracellular layer.