Associated with the endoplasmic reticulum. Cell structure
Endoplasmic reticulum (ER) , or endoplasmic reticulum (ER), is a system consisting of membrane cisterns, channels and vesicles. About half of all cell membranes are in the ER.
Morphofunctionally, EPS is differentiated into 3 sections: rough (granular), smooth (agranular), and intermediate. On the granular ER are ribosomes (PC), smooth and intermediate are deprived of them. The granular ER is mainly represented by cisterns, while the smooth and intermediate ER is mainly represented by canals. The membranes of tanks, channels and bubbles can pass into each other. ER contains a semi-liquid matrix characterized by a specific chemical composition.
ER functions:
- compartmentalization;
- synthetic;
- transport;
- detoxification;
- regulation of the concentration of calcium ions.
Compartmentalization function
associated with cell division into compartments (compartments) using ER membranes. Such a division makes it possible to isolate part of the contents of the cytoplasm from the hyaloplasm and enables the cell to separate and localize certain processes, as well as to force them to proceed more efficiently and directionally.
synthetic function.
Almost all lipids are synthesized on the smooth ER, with the exception of two mitochondrial lipids, the synthesis of which occurs in the mitochondria themselves. Cholesterol is synthesized on the membranes of the smooth ER (in humans, up to 1 g per day, mainly in the liver; with liver damage, the amount of cholesterol in the blood drops, the shape and function of red blood cells change, and anemia develops).
Protein synthesis occurs on the rough ER:
- the internal phase of the ER, the Golgi complex, lysosomes, mitochondria;
- secretory proteins, eg hormones, immunoglobulins;
- membrane proteins.
Protein synthesis begins on free ribosomes in the cytosol. After chemical transformations, proteins are packaged into membrane vesicles, which are cleaved off from the ER and transported to other areas of the cell, for example, to the Golgi complex.
Proteins synthesized on the ER can be conditionally divided into two streams:
- internal, which remain in the ER;
- external, which do not remain in the ER.
Internal proteins, in turn, can also be divided into two streams:
- resident, not leaving the ER;
- transit, leaving the ER.
In the ER is happening detoxification of harmful substances
trapped in the cell or formed in the cell itself. Most harmful substances are
hydrophobic substances, which therefore cannot be excreted in the urine. The ER membranes contain the cytochrome P450 protein, which converts hydrophobic substances into hydrophilic ones, and after that they are removed from the body in the urine.
A bit of history
The cell is considered the smallest structural unit of any organism, however, it also consists of something. One of its components is the endoplasmic reticulum. Moreover, EPS is a mandatory component of any cell in principle (except for some viruses and bacteria). It was discovered by the American scientist K. Porter back in 1945. It was he who noticed the systems of tubules and vacuoles, which, as it were, accumulated around the nucleus. Porter also noted that the sizes of EPS in the cells of different creatures and even organs and tissues of the same organism are not similar to each other. He came to the conclusion that this is due to the functions of a particular cell, the degree of its development, as well as the stage of differentiation. For example, in humans, EPS is very well developed in the cells of the intestines, mucous membranes and adrenal glands.
concept
EPS is a system of tubules, tubules, vesicles and membranes that are located in the cytoplasm of the cell.
Endoplasmic reticulum: structure and functions
Structure | |
First, it is a transport function. Like the cytoplasm, the endoplasmic reticulum provides for the exchange of substances between organelles. Secondly, ER performs structuring and grouping of the contents of the cell, breaking it into certain sections. Thirdly, the most important function is protein synthesis, which is carried out in the ribosomes of the rough endoplasmic reticulum, as well as the synthesis of carbohydrates and lipids, which occurs on the membranes of the smooth EPS. |
|
EPS structure In total, there are 2 types of endoplasmic reticulum: granular (rough) and smooth. The functions performed by this component depend on the type of the cell itself. On membranes smooth network there are departments that produce enzymes, which are then involved in metabolism. The rough endoplasmic reticulum contains ribosomes on its membranes. |
Brief information about the other most important components of the cell
Cytoplasm: structure and functions
| Image | Structure | Functions |
| It is the fluid in the cell. It is in it that all organelles are located (including the Golgi apparatus, and the endoplasmic reticulum, and many others) and the nucleus with its contents. Refers to the mandatory components and is not an organoid as such. | The main function is transport. It is thanks to the cytoplasm that all organelles interact, their ordering (fold into a single system) and the flow of all chemical processes. |
Cell membrane: structure and functions
| Image | Structure | Functions |
| Molecules of phospholipids and proteins, forming two layers, make up the membrane. It is the thinnest film that envelops the entire cell. Its integral component is also polysaccharides. And in plants outside, it is still covered with a thin layer of fiber. | The main function of the cell membrane is to limit the internal contents of the cell (cytoplasm and all organelles). Since it contains the smallest pores, it provides transport and metabolism. It can also be a catalyst in the implementation of some chemical processes and a receptor in the event of an external danger. |
Core: structure and functions
| Image | Structure | Functions |
| It is either oval or spherical in shape. It contains special DNA molecules, which in turn carry the hereditary information of the whole organism. The core itself is covered on the outside with a special shell in which there are pores. It also contains nucleoli (small bodies) and liquid (juice). Around this center is the endoplasmic reticulum. | It is the nucleus that regulates absolutely all processes occurring in the cell (metabolism, synthesis, etc.). And it is this component that is the main carrier of hereditary information of the whole organism. The nucleolus is where protein and RNA are synthesized. |
Ribosomes
They are organelles that provide basic protein synthesis. They can be located both in the free space of the cytoplasm of the cell, and in combination with other organelles (endoplasmic reticulum, for example). If the ribosomes are located on the membranes of the rough EPS (being on the outer walls of the membranes, the ribosomes create roughness) , the efficiency of protein synthesis increases several times. This has been proven by numerous scientific experiments.
Golgi complex
An organoid consisting of several cavities that constantly secrete bubbles of various sizes. The accumulated substances are also used for the needs of the cell and the body. The Golgi complex and the endoplasmic reticulum are often located side by side.
Lysosomes
Organelles surrounded by a special membrane and performing the digestive function of the cell are called lysosomes.
Mitochondria
Organelles surrounded by several membranes and performing an energy function, that is, providing the synthesis of ATP molecules and distributing the energy received throughout the cell.
Plastids. Types of plastids
Chloroplasts (function of photosynthesis);
Chromoplasts (accumulation and preservation of carotenoids);
Leukoplasts (accumulation and storage of starch).
Organelles designed for locomotion
They also make some movements (flagella, cilia, long processes, etc.).
Cell center: structure and functions
14. Eps granular and smooth. The structure and features of functioning in cells of the same type.
Endoplasmic reticulum (EPS) - a system of communicating or separate tubular channels and flattened cisterns located throughout the cytoplasm of the cell. They are delimited by membranes (membrane organelles). Sometimes tanks have expansions in the form of bubbles. EPS channels can connect with surface or nuclear membranes, contact with the Golgi complex.
In this system, smooth and rough (granular) EPS can be distinguished.
Rough EPS. On the channels of the rough ER, ribosomes are located in the form of polysomes. Here, the synthesis of proteins occurs, mainly produced by the cell for export (removal from the cell), for example, secretions of glandular cells. Here, the formation of lipids and proteins of the cytoplasmic membrane and their assembly take place. The densely packed cisterns and channels of the granular ER form a layered structure where protein synthesis proceeds most actively. This place is called ergastoplasm.
Smooth EPS. There are no ribosomes on smooth ER membranes. Here, mainly the synthesis of fats and similar substances (for example, steroid hormones), as well as carbohydrates, proceeds. Through the channels of smooth EPS, the finished material also moves to the place of its packaging into granules (to the zone of the Golgi complex). In hepatic cells, smooth ER takes part in the destruction and neutralization of a number of toxic and medicinal substances (for example, barbiturates). In the striated muscles, the tubules and cisterns of the smooth ER deposit calcium ions.
15. Golgi complex. Structure and functions.
The Golgi complex is a membrane structure inherent in any eukaryotic cell. The Golgi complex consists of flattened cisterns, usually arranged in stacks (dictyosomes). The tanks are not isolated, but are interconnected by a system of tubes. The first cistern from the nucleus is called the cis-pole of the Golgi complex, and the last, respectively, the trans-pole. The number of cisterns in different cells of different organisms may vary, but in general, the structure of the Golgi complex in all eukaryotes is approximately the same. In secretory cells, it is especially strongly developed. The functions of the Golgi complex are to transport proteins to their destination, as well as their glycosylation, deglycosylation, and modification of oligosaccharide chains.
The Golgi complex is characterized by functional anisotropy. Newly synthesized proteins are transported from the endoplasmic reticulum to the cis-pole of dictyosomes using vesicles. Then they gradually move towards the trans-pole, undergoing gradual modifications (as they move away from the nucleus, the composition of the enzyme systems in the tanks changes). Finally, the proteins travel to their final destination in vesicles budding from the trans pole. The Golgi complex provides protein transport to three compartments: to lysosomes (as well as to the central vacuole plant cell and contractile vacuoles of protozoa), to the cell membrane and into the intercellular space. The direction of protein transfer is determined by special glycosidic labels. For example, a marker for lysosomal enzymes is mannose-6-phosphate. The maturation and transport of mitochondrial, nuclear and chloroplast proteins occurs without the participation of the Golgi complex: they are synthesized by free ribosomes and then enter directly into the cytosol. An important function of the Golgi complex is the synthesis and modification of the carbohydrate component of glycoproteins, proteoglycans and glycolipids. It also synthesizes many polysaccharides, such as hemicellulose and pectin in plants. The cisternae of the Golgi complex contain a whole range of different glycosyltransferases and glycosidases. They also undergo sulfation of carbohydrate residues.
Cells, which is a branched system of flattened cavities surrounded by a membrane, vesicles and tubules.
Schematic representation of the cell nucleus, endoplasmic reticulum, and Golgi complex.
(1) Cell nucleus.
(2) The pores of the nuclear membrane.
(3) Granular endoplasmic reticulum.
(4) Agranular endoplasmic reticulum.
(5) Ribosomes on the surface of the granular endoplasmic reticulum.
(6) Transported proteins.
(7) Transport vesicles.
(8) Golgi complex.
(9)
(10)
(11)
Discovery history
For the first time, the endoplasmic reticulum was discovered by the American scientist C. Porter in 1945 using electron microscopy.
Structure
The endoplasmic reticulum consists of an extensive network of tubules and pockets surrounded by a membrane. The area of the membranes of the endoplasmic reticulum is more than half of the total area of all cell membranes.
The ER membrane is morphologically identical to the shell of the cell nucleus and is one with it. Thus, the cavities of the endoplasmic reticulum open into the intermembrane cavity nuclear envelope. EPS membranes provide active transport of a number of elements against a concentration gradient. The filaments that form the endoplasmic reticulum are 0.05-0.1 µm in diameter (sometimes up to 0.3 µm), the thickness of the two-layer membranes that form the wall of the tubules is about 50 angstroms (5 nm, 0.005 µm). These structures contain unsaturated phospholipids, as well as some cholesterol and sphingolipids. They also contain proteins.
The tubules, the diameter of which ranges from 0.1-0.3 µm, are filled with homogeneous contents. Their function is the implementation of communication between the contents of the EPS bubbles, external environment and the cell nucleus.
The endoplasmic reticulum is not a stable structure and is subject to frequent changes.
There are two types of EPR:
- granular endoplasmic reticulum
- agranular (smooth) endoplasmic reticulum
On the surface of the granular endoplasmic reticulum there is a large number of ribosomes, which are absent on the surface of the agranular ER.
The granular and agranular endoplasmic reticulum perform different functions in the cell.
Functions of the endoplasmic reticulum
With the participation of the endoplasmic reticulum, translation and transport of proteins, synthesis and transport of lipids and steroids occur. EPS is also characterized by the accumulation of synthesis products. The endoplasmic reticulum is also involved in the creation of a new nuclear membrane (for example, after mitosis). The endoplasmic reticulum contains an intracellular supply of calcium, which is, in particular, a mediator of muscle cell contraction. In the cells of muscle fibers there is a special form of the endoplasmic reticulum - sarcoplasmic reticulum.
Functions of the agranular endoplasmic reticulum
The agranular endoplasmic reticulum is involved in many metabolic processes. Enzymes of the agranular endoplasmic reticulum are involved in the synthesis of various lipids and phospholipids, fatty acids, and steroids. Also, the agranular endoplasmic reticulum plays an important role in carbohydrate metabolism, cell disinfection and calcium storage. In particular, in connection with this, the agranular endoplasmic reticulum predominates in the cells of the adrenal glands and liver.
Synthesis of hormones
Hormones that are formed in the agranular EPS include, for example, vertebrate sex hormones and adrenal steroid hormones. The testicular and ovarian cells responsible for hormone synthesis contain large amounts of agranular endoplasmic reticulum.
Accumulation and conversion of carbohydrates
Carbohydrates in the body are stored in the liver in the form of glycogen. Glycolysis converts glycogen in the liver into glucose, which is a critical process in maintaining blood glucose levels. One of the agranular EPS enzymes cleaves off a phospho group from the first product of glycolysis, glucose-6-phosphate, thus allowing glucose to leave the cell and raise blood sugar levels.
Neutralization of poisons
The smooth endoplasmic reticulum of the liver cells is actively involved in the neutralization of all kinds of poisons. The smooth ER enzymes attach the molecules of active substances encountered, which can thus be dissolved more quickly. In the case of continuous intake of poisons, drugs or alcohol, a larger amount of agranular ESR is formed, which increases the dose of the active substance necessary to achieve the same effect.
Sarcoplasmic reticulum
A special form of the agranular endoplasmic reticulum, the sarcoplasmic reticulum, forms the ER in muscle cells, in which calcium ions are actively pumped from the cytoplasm into the ER cavity against the concentration gradient in the unexcited state of the cell and released into the cytoplasm to initiate contraction. The concentration of calcium ions in the EPS can reach 10 −3 mol, while in the cytosol it is about 10 −7 mol (at rest). Thus, the sarcoplasmic reticulum membrane provides active transport against high-order concentration gradients. And the intake and release of calcium ions in the EPS is in a subtle relationship with physiological conditions.
The concentration of calcium ions in the cytosol affects many intracellular and intercellular processes, such as: activation or inhibition of enzymes, gene expression, synaptic plasticity of neurons, contractions of muscle cells, release of antibodies from cells of the immune system.
Functions of the granular endoplasmic reticulum
The granular endoplasmic reticulum has two functions: protein synthesis and membrane production.
Protein synthesis
Proteins produced by the cell are synthesized on the surface of ribosomes, which can be attached to the surface of the ER. The resulting polypeptide chains are placed in the cavity of the granular endoplasmic reticulum (where the polypeptide chains synthesized in the cytosol also fall), where they are subsequently cut off and folded in the right way. Thus, linear amino acid sequences are obtained after translocation into the endoplasmic reticulum the necessary three-dimensional structure, after which they are re-transferred into the cytosol.
Membrane synthesis
Ribosomes attached to the surface of the granular ER produce proteins, which, along with the production of phospholipids, among other things, expands the intrinsic surface of the ER membrane, which sends membrane fragments to other parts of the membrane system via transport vesicles.
See also
- Reticulons are proteins of the endoplasmic reticulum.
Wikimedia Foundation. 2010 .
ENDOPLASMATIC NETWORK, a system of membranes and channels in the CYTOPLASMA of EUKARYOTIC cells (that is, those with a nucleus) of plants, animals, fungi. Serves to transport substances within the cell. Parts of the endoplasmic reticulum are covered with tiny granules that carry ... ... Scientific and technical encyclopedic Dictionary
- (endoplasmic reticulum), cellular organoid; a system of tubules, vesicles and "cisterns" delimited by membranes. Located in the cytoplasm of the cell. Participates in metabolic processes, ensuring the transport of substances from environment V… … encyclopedic Dictionary
endoplasmic reticulum- endoplazminis tinklas statusas T sritis augalininkystė apibrėžtis Submikroskopinis ląstelės organoidas, sudarytas iš citoplazmoje išsiskaidžiusių ir tarpusavyje sudarančių sistemą kanalėlių ir pūsleėlių, atlie metaboliste lų transport ų… … Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas
- (ndo + (cyto) plasma; synonym: cytoplasmic reticulum, endoplasmic reticulum) organoid, which is a system of tubules, vacuoles and cisterns located in the cytoplasm, delimited by membranes; provides transport of substances to ... ... Big medical dictionary
- (biol.) intracellular organoid, represented by a system of flat tanks, tubules and vesicles limited by membranes; provides mainly the movement of substances from the environment into the cytoplasm and between intracellular ... ... Big soviet encyclopedia
- (see endo ... + plasma) otherwise ergastoplasm is an intracellular organoid consisting of cavities various shapes and sizes (vesicles, tubules and cisterns) surrounded by a membrane 2. New dictionary foreign words. by EdwART, 2009 … Dictionary of foreign words of the Russian language
- (endoplasmic reticulum), cellular organoid; a system of tubules, vesicles and cisterns delimited by membranes. Located in the cytoplasm of the cell. Participates in metabolic processes, providing transport to and from the environment to the cytoplasm and ... ... Natural science. encyclopedic Dictionary
endoplasmic reticulum- see endoplasmic reticulum ... Plant anatomy and morphology
Organelles general meaning. Endoplasmic reticulum.
Organelles - structures constantly present in the cytoplasm, specialized in performing certain functions in the cell. They are divided into organelles of general and special significance.
The endoplasmic reticulum, or endoplasmic reticulum, is a system of flat membrane cisterns and membrane tubules. Membrane tanks and tubules are interconnected and form a membrane structure with a common content. This allows you to isolate certain areas cytoplasm from the main nialoplasm and implement some specific cellular functions in them. As a result, functional differentiation of various zones of the cytoplasm occurs. The structure of EPS membranes corresponds to the fluid-mosaic model. Morphologically, there are 2 types of EPS: smooth (agranular) and rough (granular). Smooth ER is represented by a system of membrane tubules. Rough EPS is a system of membrane tanks. On the outer side of the rough EPS membranes are ribosomes. Both types of EPS are structurally dependent - membranes of one type of EPS can pass into membranes of another type.
Functions of the endoplasmic reticulum:
1. Granular EPS is involved in the synthesis of proteins, complex protein molecules are formed in the channels.
2. Smooth ER is involved in the synthesis of lipids and carbohydrates.
3.Transport organic matter into the cell (via ER channels).
4. Divides the cell into sections - in which different chemical reactions and physiological processes.
Smooth EPS is multifunctional. In its membrane there are proteins-0 enzymes that catalyze the reactions of synthesis of membrane lipids. In smooth ER, some non-membrane lipids (steroid hormones) are also synthesized. Ca2+ carriers are included in the composition of the membrane of this type of EPS. They transport calcium along a concentration gradient (passive transport). In passive transport, ATP is synthesized. With their help, the Ca2+ concentration in the hyaloplasm is regulated in the smooth EPS. This parameter is important for the regulation of microtubules and microfibrils. In muscle cells, smooth ER regulates muscle contraction. In the EPS, detoxification of many substances harmful to the cell (drugs) occurs. Smooth ER can form membranous vesicles, or microbodies. Such vesicles carry out specific oxidative reactions in isolation from EPS.
main function rough eps is protein synthesis. This is determined by the presence of ribosomes on the membranes. In the membrane of the rough EPS there are special proteins ribophorins. Ribosomes interact with ribophorins and are fixed on the membrane in a certain orientation. All proteins synthesized in the ER have a terminal signal fragment. On the ribosomes of the rough ER, three types of proteins are synthesized:
1. Membrane proteins. All proteins of the plasmolemma, the membranes of the ER itself, and most of the proteins of other organelles are products of the ER ribosomes.
2. Secretory proteins. These proteins enter the endoplasmic reticulum and are then expelled from the cell by exocytosis.
3. Intraorganoid proteins. These proteins are localized and function in the cavities of membrane organelles: the ER itself, the Golgi complex, lysosomes, and mitochondria. EPS is involved in the formation of biomembranes.
In cisterns of rough ER, post-translational modification of proteins occurs.
EPS is a universal organelle of eukaryotic cells. Violation of the structure and function of the EPS leads to serious consequences. EPS is the site of formation of membrane vesicles with specialized functions (peroxisomes).
