Chemical composition plasmolemma.

Plasmolemma basis of lipoprotein complexes. It has a thickness of about 10 nm, and thus is the thickest of the cell membranes.

Located outside the plasmolemma nadmembranny layer - glycocalyx (glycocalyx). The thickness of this layer is about 3.4 nm, it is found in virtually all animal cells, but the degree of severity varies. Glycocalyx is associated with plasmolemma glycoprotein complex, which is composed of various carbohydrates. Carbohydrates form long, branched chain polysaccharides associated with proteins and lipids that make up plasmolemma (see. Fig. 5). When using special methods of detecting polysaccharides (dye ruthenium red) that they form a sort of cover over the plasma mambrany.

In glycocalyx may be located proteins not directly related to bilipidnym layer. Typically, enzymes are proteins involved in the extracellular cleavage of various substances, such as carbohydrates, proteins, fats, and others.

Plasmolemma function. This membrane performs several important cellular functions, of which are leading barrier function (differentiation with the external environment of the cytoplasm), the function of reception and transport of various substances into the cell as well as from it.

Receptor function related to the localization on plasmolemma special structures involved in specific "recognition" of chemical and physical factors. Cell surface has a large number of components - receptors that determine the possibility of specific reactions with various agents. Receptors on the cell surface may serve as a membrane glycoproteins and glycolipids (see. Fig. 5). It is believed that these substances are sensitive to the individual portions may be scattered over the entire surface or cells are collected in a small zone. There are receptors for biologically active substances - hormones, neurotransmitters, antigens specific to different cells or certain proteins.

With specific localization plasmolemma linked receptors responsible for important processes such as the mutual recognition of cells develop immunity receptors that respond to physical factors. Thus, in animal cells plasmolemma photosensitive system has a special photoreceptor protein (rhodopsin) with which the light signal is converted into the chemical, which in turn leads to the generation of an electric pulse.

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