home › Tires and wheels › Golgi apparatus of plant and animal cells. Golgi complex, its structure and functions

Golgi apparatus of plant and animal cells. Golgi complex, its structure and functions

Golgi apparatus (Golgi complex) - AG

The structure known today as complex or golgi apparatus (AG) first discovered in 1898 by the Italian scientist Camillo Golgi

It was possible to study in detail the structure of the Golgi complex much later using an electron microscope.

AG is a stack of flattened "tanks" with widened edges. A system of small single-membrane vesicles (Golgi vesicles) is associated with them. Each stack usually consists of 4-6 "tanks", is a structural and functional unit of the Golgi apparatus and is called a dictyosome. The number of dictyosomes in a cell ranges from one to several hundred.

The Golgi apparatus is usually located near the cell nucleus, near the EPS (in animal cells often near the cell center).

Golgi complex

On the left - in the cell, among other organelles.

On the right is the Golgi complex with membrane vesicles separating from it.

All substances synthesized on EPS membranes transferred to golgi complex V membrane vesicles, which bud off from the ER and then merge with the Golgi complex. Arrived organic substances from EPS undergo further biochemical transformations, accumulate, are packed into membranous vesicles and delivered to those places in the cell where they are needed. They are involved in building cell membrane or stand out ( are secreted) from the cell.

Functions of the Golgi apparatus:

1 Participation in the accumulation of products synthesized in the endoplasmic reticulum, in their chemical rearrangement and maturation. In the tanks of the Golgi complex, polysaccharides are synthesized and complexed with protein molecules.

2) Secretory - the formation of ready-made secretory products that are excreted outside the cell by exocytosis.

3) Renewal of cell membranes, including sections of the plasmolemma, as well as replacement of defects in the plasmolemma during the secretory activity of the cell.

4) Place of formation of lysosomes.

5) Transport of substances

Lysosomes

The lysosome was discovered in 1949 by C. de Duve ( Nobel Prize for 1974).

Lysosomes- single-membrane organelles. They are small bubbles (diameter from 0.2 to 0.8 microns) containing a set of hydrolytic enzymes - hydrolases. A lysosome can contain from 20 to 60 various kinds hydrolytic enzymes (proteinases, nucleases, glucosidases, phosphatases, lipases, etc.) that break down various biopolymers. The breakdown of substances by enzymes is called lysis (lysis-decay).

Lysosome enzymes are synthesized on the rough ER, move to the Golgi apparatus, where they are modified and packaged into membrane vesicles, which, after separation from the Golgi apparatus, become lysosomes proper. (Lysosomes are sometimes called the "stomachs" of the cell)

Lysosome - Membrane vesicle containing hydrolytic enzymes

Functions of lysosomes:

1. Cleavage of substances absorbed as a result of phagocytosis and pinocytosis. Biopolymers are broken down into monomers that enter the cell and are used for its needs. For example, they can be used to synthesize new organic matter or may be further broken down for energy.

2. Destroy old, damaged, excess organelles. Destruction of organelles can also occur during starvation of the cell.

3. Carry out autolysis (self-destruction) of the cell (liquefaction of tissues in the area of inflammation, destruction of cartilage cells in the process of bone tissue formation, etc.).

Autolysis - This self-destruction cells resulting from the release of contents lysosomes inside the cell. Because of this, lysosomes are jokingly called "suicide tools" Autolysis is a normal phenomenon of ontogeny; it can spread both to individual cells and to the entire tissue or organ, as occurs during resorption of the tadpole's tail during metamorphosis, i.e., during the transformation of a tadpole into a frog

Endoplasmic reticulum, Golgi apparatus and lysosomesform single vacuolar system of the cell, individual elements of which can pass into each other during the rearrangement and change in the function of membranes.

Mitochondria

The structure of the mitochondria:
1 - outer membrane;
2 - inner membrane; 3 - matrix; 4 - crista; 5 - multienzyme system; 6 - circular DNA.

The shape of the mitochondria can be rod-shaped, round, spiral, cup-shaped, branched. The length of mitochondria ranges from 1.5 to 10 microns, the diameter is from 0.25 to 1.00 microns. The number of mitochondria in a cell can reach several thousand and depends on the metabolic activity of the cell.

Mitochondria is limited two membranes . The outer membrane of mitochondria is smooth, the inner one forms numerous folds - cristae. The cristae increase the surface area of the inner membrane. The number of cristae in mitochondria can vary depending on the energy needs of the cell. It is on the inner membrane that numerous enzyme complexes involved in the synthesis of adenosine triphosphate (ATP) are concentrated. Here, the energy of chemical bonds is converted into energy-rich (macroergic) bonds of ATP . Besides, in the mitochondria, fatty acids and carbohydrates are broken down with the release of energy, which is accumulated and used for the processes of growth and synthesis.The internal environment of these organelles is called matrix. It contains circular DNA and RNA, small ribosomes. Interestingly, mitochondria are semi-autonomous organelles, since they depend on the functioning of the cell, but at the same time they can maintain a certain independence. So, they are able to synthesize their own proteins and enzymes, as well as reproduce on their own (mitochondria contain their own DNA chain, in which up to 2% of the DNA of the cell itself is concentrated).

Mitochondrial functions:

1. Converting the energy of chemical bonds into macroergic bonds of ATP (mitochondria are the "energy stations" of the cell).

2. Participate in the processes of cellular respiration - oxygen breakdown of organic substances.

Ribosomes

The structure of the ribosome:
1 - large subunit; 2 - small subunit.

Ribosomes - non-membrane organelles, about 20 nm in diameter. Ribosomes consist of two fragments - large and small subunits. The chemical composition of ribosomes - proteins and rRNA. rRNA molecules make up 50–63% of the mass of the ribosome and form its structural framework.

During protein biosynthesis, ribosomes can "work" singly or combine into complexes - polyribosomes (polysomes). In such complexes, they are linked to each other by a single mRNA molecule.

Ribosome subunits are formed in the nucleolus. Passing through the pores nuclear envelope ribosomes enter the membranes of the endoplasmic reticulum (ER).

Ribosome function: assembly of a polypeptide chain (synthesis of protein molecules from amino acids).

cytoskeleton

The cellular cytoskeleton is formed microtubules And microfilaments .

microtubules are cylindrical formations with a diameter of 24 nm. Their length is 100 µm-1 mm. The main component is a protein called tubulin. It is incapable of contraction and can be destroyed by colchicine.

Microtubules are located in the hyaloplasm and perform the following functions:

create an elastic, but at the same time, a strong frame of the cell, which allows it to maintain its shape;

take part in the process of distribution of cell chromosomes (form a division spindle);

provide movement of organelles;

Microfilaments- filaments that are located under the plasma membrane and consist of the protein actin or myosin. They can contract, resulting in movement of the cytoplasm or protrusion of the cell membrane. In addition, these components are involved in the formation of constriction during cell division.

Cell Center

The cell center is an organoid consisting of 2 small granules - centrioles and a radiant sphere around them - the centrosphere. A centriole is a cylindrical body 0.3-0.5 µm long and about 0.15 µm in diameter. The walls of the cylinder consist of 9 parallel tubes. Centrioles are arranged in pairs at right angles to each other. The active role of the cell center is revealed during cell division. Before cell division, centrioles diverge to opposite poles, and a daughter centriole appears near each of them. They form a spindle of division, which contributes to the uniform distribution of genetic material between daughter cells.

Centrioles are self-reproducing organelles of the cytoplasm, they arise as a result of duplication of already existing centrioles.

Functions:

1. Ensuring uniform divergence of chromosomes to the poles of the cell during mitosis or meiosis.

2. Center for the organization of the cytoskeleton.

Organelles of movement

Not present in all cells

The organelles of movement include cilia, as well as flagella. These are tiny growths in the form of hairs. The flagellum contains 20 microtubules. Its base is located in the cytoplasm and is called the basal body. The length of the flagellum is 100 µm or more. Flagella that are only 10-20 microns are called cilia . When microtubules slide, cilia and flagella are able to oscillate, causing movement of the cell itself. The cytoplasm may contain contractile fibrils called myofibrils. Myofibrils, as a rule, are located in myocytes - muscle tissue cells, as well as in heart cells. They are made up of smaller fibers (protofibrils).

In animals and humans cilia they cover the airways and help to get rid of small solid particles such as dust. In addition, there are also pseudopods that provide amoeboid movement and are elements of many unicellular and animal cells (for example, leukocytes).

Functions:

Specific

Core. Chromosomes

Golgi complex is a membrane structure inherent in any eukaryotic cell.

The Golgi apparatus is represented flattened tanks(or bags) collected in a pile. Each tank is slightly curved and has convex and concave surfaces. The average diameter of the tanks is about 1 micron. In the center of the tank, its membranes are brought together, and on the periphery they often form extensions, or ampoules, from which they lace up. bubbles. Packages of flat tanks with an average of about 5-10 form dictyosome. In addition to cisterns, the Golgi complex contains transport and secretory vesicles. In the dictyosome, two surfaces are distinguished in accordance with the direction of curvature of the curved surfaces of the cisterns. The convex surface is called immature, or cis-surface. It faces the nucleus or tubules of the granular endoplasmic reticulum and is connected with the latter by vesicles that detach from the granular reticulum and bring protein molecules into the dictyosome for maturation and formation into the membrane. The opposite transsurface of the dictyosome is concave. It faces the plasmolemma and is called mature because secretory vesicles are laced from its membranes, containing secretion products ready for removal from the cell.

The Golgi complex is involved in:

in the accumulation of products synthesized in the endoplasmic reticulum,
in their chemical restructuring and maturation.

IN cisterns of the Golgi complex there is a synthesis of polysaccharides, their complexation with protein molecules.

One of main functions Golgi complex - formation of finished secretory products, which are removed from the cell by exocytosis. The most important functions of the Golgi complex for the cell are also renewal of cell membranes, including sections of the plasmolemma, as well as the replacement of defects in the plasmolemma during the secretory activity of the cell.

The Golgi complex is considered source of formation of primary lysosomes, although their enzymes are also synthesized in the granular network. Lysosomes are intracellularly formed secretory vacuoles filled with hydrolytic enzymes necessary for the processes of phago- and autophagocytosis. At the light-optical level, lysosomes can be identified and judged on the degree of their development in the cell by the activity of the histochemical reaction to acid phosphatase, the key lysosomal enzyme. Under electron microscopy, lysosomes are defined as vesicles, limited from the hyaloplasm by a membrane. Conventionally, there are 4 main types of lysosomes:

primary,
secondary lysosomes,
autophagosomes,
residual bodies.

Primary lysosomes- these are small membrane vesicles (their average diameter is about 100 nm), filled with a homogeneous finely dispersed content, which is a set of hydrolytic enzymes. About 40 enzymes (proteases, nucleases, glycosidases, phosphorylases, sulfatases) have been identified in lysosomes, the optimal mode of action of which is designed for an acidic environment (pH 5). Lysosomal membranes contain special carrier proteins for transport from the lysosome to the hyaloplasm of hydrolytic cleavage products - amino acids, sugars and nucleotides. The lysosome membrane is resistant to hydrolytic enzymes.

Secondary lysosomes are formed by the fusion of primary lysosomes with endocytic or pinocytic vacuoles. In other words, secondary lysosomes are intracellular digestive vacuoles, the enzymes of which are supplied by primary lysosomes, and the material for digestion is supplied by endocytic (pinocytic) vacuoles. The structure of secondary lysosomes is very diverse and changes in the process of hydrolytic cleavage of the contents. Lysosome enzymes break down those that enter the cell biological substances, resulting in the formation of monomers that are transported through the lysosome membrane to the hyaloplasm, where they are utilized or included in various synthetic and metabolic reactions.

If the cell's own structures (senescent organelles, inclusions, etc.) undergo interaction with primary lysosomes and hydrolytic cleavage by their enzymes, a autophagosome. Autophagocytosis is a natural process in the life of a cell and plays an important role in the renewal of its structures during intracellular regeneration.

Residual bodies this is one of the final stages of the existence of phago- and autolysosomes and is found during incomplete phago- or autophagocytosis and subsequently isolated from the cell by exocytosis. They have a compacted content, often there is a secondary structuring of undigested compounds (for example, lipids form complex layered formations).

Structure

The Golgi complex is a stack of disk-shaped membranous sacs (cistern), somewhat expanded closer to the edges, and the system of Golgi vesicles associated with them. In plant cells, a number of separate stacks (dictyosomes) are found, in animal cells there is often one large or several stacks connected by tubes.

In the Golgi complex, there are 3 sections of cisterns surrounded by membrane vesicles:

Cis-section (closest to the nucleus);
Medial department;
Trans-section (the most distant from the core).

These departments differ from each other by a set of enzymes. In the cis-section, the first cistern is called the "cistern of salvation", since with its help the receptors coming from the intermediate endoplasmic reticulum return back. Enzyme of the cis-section: phosphoglycosidase (attaches phosphate to the carbohydrate - mannase). In the medial section there are 2 enzymes: mannasidase (cleaves off mannase) and N-acetylglucosamine transferase (attaches certain carbohydrates - glycosamines). In the trans section, enzymes: peptidase (carries out proteolysis) and transferase (carries out the transfer of chemical groups).

Functions

Protein segregation into 3 streams:
- lysosomal - glycosylated proteins (with mannose) enter the cis-section of the Golgi complex, some of them are phosphorylated, a marker of lysosomal enzymes is formed - mannose-6-phosphate. In the future, these phosphorylated proteins will not undergo modification, but will enter the lysosomes.
- constitutive exocytosis (constitutive secretion). This flow includes proteins and lipids, which become components of the surface apparatus of the cell, including the glycocalyx, or they can be part of the extracellular matrix.
- Induced secretion - proteins that function outside the cell, the surface apparatus of the cell, in the internal environment of the body get here. characteristic of secretory cells.
Formation of mucous secretions - glycosaminoglycans (mucopolysaccharides)
Formation of carbohydrate components of the glycocalyx - mainly glycolipids.
Sulfation of carbohydrate and protein components of glycoproteins and glycolipids
Partial proteolysis of proteins - sometimes due to this, an inactive protein becomes active (proinsulin is converted to insulin).

Transport of substances from the endoplasmic reticulum

The Golgi apparatus is asymmetric - tanks located closer to the cell nucleus ( cis-Golgi) contain the least mature proteins, membrane vesicles continuously join these tanks - vesicles, budding from the granular endoplasmic reticulum(EPR), on the membranes of which the synthesis of proteins by ribosomes occurs. The movement of proteins from the endoplasmic reticulum (ER) to the Golgi apparatus occurs indiscriminately, however, incompletely or incorrectly folded proteins remain in the ER. The return of proteins from the Golgi apparatus to the ER requires a specific signal sequence (lysine-asparagine-glutamine-leucine) and occurs due to the binding of these proteins to membrane receptors in the cis-Golgi.

Protein modification in the Golgi apparatus

In the tanks of the Golgi apparatus, proteins intended for secretion, transmembrane proteins of the plasma membrane, proteins of lysosomes, etc. mature. The maturing proteins sequentially move through the tanks into organelles, in which their modifications occur - glycosylation and phosphorylation. In O-glycosylation, complex sugars are attached to proteins through an oxygen atom. During phosphorylation, a residue of phosphoric acid is attached to proteins.

Different tanks of the Golgi apparatus contain different resident catalytic enzymes and, consequently, different processes sequentially occur with maturing proteins in them. It is clear that such a stepwise process must be somehow controlled. Indeed, maturing proteins are “marked” with special polysaccharide residues (mainly mannose), apparently playing the role of a kind of “quality mark”.

It is not completely understood how maturing proteins move through the cisternae of the Golgi apparatus while resident proteins remain more or less associated with one cisterna. There are two mutually non-exclusive hypotheses to explain this mechanism:

according to the first, protein transport is carried out using the same mechanisms of vesicular transport as the transport route from the ER, and resident proteins are not included in the budding vesicle;
according to the second, there is a continuous movement (maturation) of the tanks themselves, their assembly from vesicles at one end and disassembly at the other end of the organelle, and resident proteins move retrograde (in the opposite direction) using vesicular transport.

Transport of proteins from the Golgi apparatus

In the end from trance- Golgi vesicles bud containing fully mature proteins. The main function of the Golgi apparatus is the sorting of proteins passing through it. In the Golgi apparatus, the formation of a "three-directional protein flow" occurs:

maturation and transport of plasma membrane proteins;
maturation and transport of secrets;
maturation and transport of lysosome enzymes.

With the help of vesicular transport, the proteins that have passed through the Golgi apparatus are delivered “to the address” depending on the “tags” received by them in the Golgi apparatus. The mechanisms of this process are also not fully understood. It is known that the transport of proteins from the Golgi apparatus requires the participation of specific membrane receptors that recognize the "cargo" and provide selective docking of the vesicle with one or another organelle.

Lysosome formation

All hydrolytic enzymes of lysosomes pass through the Golgi apparatus, where they receive a "label" in the form of a specific sugar - mannose-6-phosphate (M6P) - as part of their oligosaccharide. Attachment of this label occurs with the participation of two enzymes. The enzyme N-acetylglucosamine phosphotransferase specifically recognizes lysosomal hydrolases by the details of their tertiary structure and adds N-acetylglucosamine phosphate to the sixth atom of several mannose residues of the hydrolase oligosaccharide. The second enzyme, phosphoglycosidase, cleaves off N-acetylglucosamine, creating an M6P label. This label is then recognized by the M6P receptor protein, with its help, hydrolases are packaged into vesicles and delivered to lysosomes. There, in an acidic environment, the phosphate is cleaved from the mature hydrolase. When N-acetylglucosamine phosphotransferase is disrupted due to mutations or genetic defects in the M6P receptor, all lysosome enzymes are delivered by default to the outer membrane and secreted into the extracellular environment. It turned out that normally a certain amount of M6P receptors also enter the outer membrane. They return those who accidentally fell into external environment lysosome enzymes into the cell during endocytosis.

Transport of proteins to the outer membrane

As a rule, even during synthesis, proteins of the outer membrane are embedded with their hydrophobic regions into the membrane of the endoplasmic reticulum. Then, as part of the vesicle membrane, they are delivered to the Golgi apparatus, and from there to the cell surface. When a vesicle merges with the plasmalemma, such proteins remain in its composition, and are not released into the external environment, like those proteins that were in the cavity of the vesicle.

Secretion

Almost all substances secreted by the cell (both protein and non-protein nature) pass through the Golgi apparatus and are packed there into secretory vesicles. So, in plants, with the participation of dictyosomes, material is secreted

The structure of the Golgi complex

Golgi complex (KG), or internal mesh apparatus , is a special part of the metabolic system of the cytoplasm, which is involved in the process of isolation and formation of cell membrane structures.

CG is visible in an optical microscope as a grid or curved rod-shaped bodies lying around the nucleus.

Under an electron microscope, it was revealed that this organelle is represented by three types of formations:

All components of the Golgi apparatus are formed by smooth membranes.

Remark 1

Occasionally, AG has a granular-mesh structure and is located near the nucleus in the form of a cap.

AG is found in all plant and animal cells.

Remark 2

The Golgi apparatus is significantly developed in the secretory cells. It is especially well seen in nerve cells.

The inner intermembrane space is filled with a matrix that contains specific enzymes.

The Golgi apparatus has two zones:

formation zone where, with the help of vesicles, material enters, which is synthesized in the endoplasmic reticulum;
ripening zone where secretion and secretory sacs are formed. This secret accumulates in the terminal areas of the AG, from where secretory vesicles bud. As a rule, such vesicles carry the secret outside the cell.
Localization of CG

In apolar cells (for example, in nerve cells), CG is located around the nucleus, in secretory cells it occupies a place between the nucleus and the apical pole.

The Golgi sac complex has two surfaces:

formative(immature or regenerative) cis-surface (from lat. Sis - on this side); functional(mature) - trans-surface (from lat. Trans - through, behind).

The Golgi column with its convex forming surface is turned towards the nucleus, adjacent to the granular endoplasmic reticulum and contains small round vesicles called intermediate. The mature concave surface of the column of sacs faces the apex (apical pole) of the cell and terminates in large vesicles.

Formation of the Golgi complex

CG membranes are synthesized by the granular endoplasmic reticulum, which is adjacent to the complex. The ER sections adjacent to it lose ribosomes, small ones, so-called, bud off from them. transport or intermediate vesicles. They move to the forming surface of the Golgi column and merge with its first sac. On the opposite (mature) surface of the Golgi complex is a sac irregular shape. Its expansion - prosecretory granules (condensing vacuoles) - continuously bud off and turn into secretory-filled vesicles - secretory granules. Thus, to the extent that the membranes of the mature surface of the complex are used for secretory vesicles, the sacs of the formation surface are replenished due to the endoplasmic reticulum.

Functions of the Golgi complex

The main function of the Golgi apparatus is the excretion of substances synthesized by the cell. These substances are transported through the cells of the endoplasmic reticulum and accumulate in the vesicles of the retinal apparatus. Then they are either released into the external environment or the cell uses them in the process of life.

The complex also concentrates some substances (for example, dyes) that enter the cell from the outside and must be removed from it.

In plant cells, the complex contains enzymes for the synthesis of polysaccharides and the polysaccharide material itself, which is used to build the cellulose membrane of the cell.

In addition, CG synthesizes those chemical substances that form the cell membrane.

In general, the Golgi apparatus performs the following functions:

accumulation and modification of macromolecules that were synthesized in the endoplasmic reticulum;
the formation of complex secrets and secretory vesicles by condensation of the secretory product;
synthesis and modification of carbohydrates and glycoproteins (formation of glycocalyx, mucus);
modification of proteins - the addition of various chemical formations to the polypeptide (phosphate - phosphorylation, carboxyl - carboxylation), the formation of complex proteins (lipoproteins, glycoproteins, mucoproteins) and the cleavage of polypeptides;
is important for the formation, renewal of the cytoplasmic membrane and other membrane formations due to the formation of membrane vesicles, which later merge with the cell membrane;
the formation of lysosomes and specific granularity in leukocytes;
formation of peroxisomes.

The protein and, in part, carbohydrate content of CG comes from the granular endoplasmic reticulum, where it is synthesized. The main part of the carbohydrate component is formed in the sacs of the complex with the participation of glycosyltransferase enzymes, which are located in the membranes of the sacs.

In the Golgi complex, cellular secretions containing glycoproteins and glycosaminoglycans are finally formed. In CG, secretory granules mature, which turn into vesicles, and the movement of these vesicles in the direction of the plasmalemma final stage secretion is the expulsion of formed (mature) vesicles outside the cell. The removal of secretory inclusions from the cell is carried out by mounting the membranes of the vesicle into the plasmalemma and the release of secretory products outside the cell. In the process of moving secretory vesicles to the apical pole of the cell, their membranes thicken from the initial 5-7 nm, reaching a plasmalemma thickness of 7-10 nm.

Remark 4

There is an interdependence between cell activity and the size of the Golgi complex - secretory cells have large columns of CG, while non-secretory cells contain a small number of sacs of the complex.

The structure of the Golgi complex

CG is visible in an optical microscope as a grid or curved rod-shaped bodies lying around the nucleus.

Under an electron microscope, it was revealed that this organelle is represented by three types of formations:

All components of the Golgi apparatus are formed by smooth membranes.

Remark 1

Occasionally, AG has a granular-mesh structure and is located near the nucleus in the form of a cap.

AG is found in all plant and animal cells.

Remark 2

The Golgi apparatus is significantly developed in the secretory cells. It is especially well seen in nerve cells.

The inner intermembrane space is filled with a matrix that contains specific enzymes.

The Golgi apparatus has two zones:

formation zone where, with the help of vesicles, material enters, which is synthesized in the endoplasmic reticulum;
ripening zone where secretion and secretory sacs are formed. This secret accumulates in the terminal areas of the AG, from where secretory vesicles bud. As a rule, such vesicles carry the secret outside the cell.
Localization of CG

In apolar cells (for example, in nerve cells), CG is located around the nucleus, in secretory cells it occupies a place between the nucleus and the apical pole.

The Golgi sac complex has two surfaces:

formative(immature or regenerative) cis-surface (from lat. Sis - on this side); functional(mature) - trans-surface (from lat. Trans - through, behind).

Formation of the Golgi complex

CG membranes are synthesized by the granular endoplasmic reticulum, which is adjacent to the complex. The ER sections adjacent to it lose ribosomes, small ones, so-called, bud off from them. transport or intermediate vesicles. They move to the forming surface of the Golgi column and merge with its first sac. On the opposite (mature) surface of the Golgi complex is an irregularly shaped sac. Its expansion - prosecretory granules (condensing vacuoles) - continuously bud off and turn into secretory-filled vesicles - secretory granules. Thus, to the extent that the membranes of the mature surface of the complex are used for secretory vesicles, the sacs of the formation surface are replenished due to the endoplasmic reticulum.

Functions of the Golgi complex

The complex also concentrates some substances (for example, dyes) that enter the cell from the outside and must be removed from it.

In plant cells, the complex contains enzymes for the synthesis of polysaccharides and the polysaccharide material itself, which is used to build the cellulose membrane of the cell.

In addition, CG synthesizes those chemicals that form the cell membrane.

In general, the Golgi apparatus performs the following functions:

accumulation and modification of macromolecules that were synthesized in the endoplasmic reticulum;
the formation of complex secrets and secretory vesicles by condensation of the secretory product;
synthesis and modification of carbohydrates and glycoproteins (formation of glycocalyx, mucus);
modification of proteins - the addition of various chemical formations to the polypeptide (phosphate - phosphorylation, carboxyl - carboxylation), the formation of complex proteins (lipoproteins, glycoproteins, mucoproteins) and the cleavage of polypeptides;
is important for the formation, renewal of the cytoplasmic membrane and other membrane formations due to the formation of membrane vesicles, which later merge with the cell membrane;
the formation of lysosomes and specific granularity in leukocytes;
formation of peroxisomes.

In the Golgi complex, cellular secretions containing glycoproteins and glycosaminoglycans are finally formed. In CG, secretory granules mature, which pass into vesicles, and the movement of these vesicles in the direction of the plasmalemma. The final stage of secretion is the expulsion of formed (mature) vesicles outside the cell. The removal of secretory inclusions from the cell is carried out by mounting the membranes of the vesicle into the plasmalemma and the release of secretory products outside the cell. In the process of moving secretory vesicles to the apical pole of the cell, their membranes thicken from the initial 5-7 nm, reaching a plasmalemma thickness of 7-10 nm.

Remark 4

Popular in category: