ENDOPLASMIC RETICULUM

From Big Medical Encyclopedia

ENDOPLASMIC RETY-KULUM (Greek endon inside + plasma molded, issued; lat. reticulum grid; a synonym a cytoplasmic reticulum) — organoid of eukaryotic cells. It is formed by membranes thickness apprx. 7 nanometers, to-rye create in cytoplasm (see) a complex system of tubules, vacuoles and tanks. Sizes of intermembrane cavities E. rubles vary from 50 nanometers (tubules) to 500 nanometers and more (tank); diameter of expanded tanks can reach several micrometers. Membranes and cavities E. rubles are connected with perinuclear space, Golgi's complex and a plasma membrane (see the Cell). Division of cytoplasm membranes E. the river on separate compartments (kompartment) is of great importance for the space organization of processes of cellular metabolism.

AA. the ruble is open in 1945. Malt liquor (To. R. Porter) and sotr.

There are two types E. river — granular (rough) and agranular (smooth). Membranes granular E. rubles bear on the surface turned into a hyaloplasma a large number of ribosomes (see). Membranes agranular E. rubles do not bear ribosomes and create in cytoplasm of hl. obr. the tubules anastomosing among themselves. Agranular E. the river directly passes with places into granular. As a rule, in each cell there are both look E. river though quantitative ratios between them vary. In the cells which are actively synthesizing and cosecreting proteins dominates granular E. the ruble seen in a light microscope as a basphilic zone of cytoplasm. In 19 century attributed to such zones an important role in processes of biosynthesis. Their set in a cell is called ergasto-plasma. Agranular E. the ruble is well developed in the cells synthesizing and cosecreting a glycogen, lipids, lipoproteids, steroid hormones. In the low-differentiated cells E. the ruble is developed poorly. In erythrocytes the endoplasmic reticulum is absent.

On ribosomes granular E. rubles are synthesized by hl. obr. secretory proteins (see Broadcasting). At synthesis of such proteins on a ribosome the so-called alarm peptide holding a ribosome on a membrane E originally forms. river. The growing polypeptide gets through a membrane into a cavity E. river where by means of a number of enzymes it is exposed to further modifications. The synthesized proteins collect in tanks E. river. From tanks E. rubles separate bubbles, to-rye transfer these proteins to Golgi's complex providing secretion of proteins from a cell (see Golgi a complex).

Second major function granular E. rubles are biosynthesis of components and assembly of membranes most E. river (agranular and granular), Golgi's complex, secretory vacuoles, lysosomes (see) and plasma membrane. Proteins of membranes are synthesized on ribosomes E. rubles are also built in membranes, without passing in a cavity E. river. The lipidic component is also synthesized on the cytoplasmatic («external») party E. the river where enzymes of synthesis of phospholipids are localized, and is at once built in a membrane. Depending on what proteins and phospholipids make the synthesized site of a membrane, it becomes a component of this or that organoid of a cell or its plasma membrane.

Agranular E. the ruble participates in synthesis and deposition of a glycogen of a hyaloplasma, in synthesis of lipids, triglycerides, etc. Agranular E. the river of hepatocytes carries out a detoxication of a number of substances, harmful to an organism, and agranular E. the river of cross-striped muscles (a sarcoplasmic reticulum) represents depot of intracellular calcium. Release and the subsequent binding of calcium ions membranes of a reticulum play an important role in processes of reduction and relaxation of muscle fiber. In cells of a mucous membrane of a stomach agranular E. the ruble participates in accumulation of the ions of chlorine necessary for synthesis salt to - you.

At damage and death of cells as a result patol. processes (e.g., defeat of motor-neurons of a spinal cord at poliomyelitis, defeat of cells of a liver owing to various intoxications) or during natural aging of 1 cells there is a loss of ribosomes, the progressing fragmentation, disintegration and lysis granular E. river. Hyperfunction of closed glands (e.g., a thyrotoxicosis) is followed by expansion of tanks, reduplication, fragmentation and vesiculation agranular E. river of cells of the corresponding gland.

Bibliography: And in c y N And. The item and Sh and x -

l and m about in V. A. Ultrastructural bases of pathology of a cell, page 85, M., 1979; 3 and-varzin A. A. and X and r and z about in and And. D. Fundamentals of the general cytology, page 127, D., 1982; Zengbush P. Molecular and cellular biology, the lane with it., t. 2, page 252, M., 1982; Ham A. and Cormac D.,

Histology, lane with English, t. 1, page 183, M., 1982; Chentsov Yu. S. General

cytology, page 188, M., 1984. Ya. E. Hesinonim

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