The Golgi apparatus is a single-membrane, microscopic organelle of a eukaryotic cell, which is designed to complete the processes of cell synthesis and ensures the removal of the formed substances.

The study of the structural components of the Golgi complex began back in 1898 by the Italian histologist Camillo Golgi, and the organelle was named after him. The study of an organoid took place for the first time as part of a nerve cell.

The structure of the Golgi complex

The lamellar complex (Golgi apparatus) has three parts:

• Cis-tank- is located near the nucleus, constantly interacts with the granular endoplasmic reticulum;
• medial tank or an intermediate part;
• trans cistern- distant from the nucleus, gives off tubular ramifications, forming a trans-Golgi network.

The lamellar complex in cells of different nature and even at different stages of differentiation of one cell, sometimes has distinctive features in the building.

Characteristic features of the Golgi apparatus

It looks like a stack, which consists of three to eight tanks, about 25 nm thick, they are flattened in the central part and expand towards the periphery, resembling a stack of inverted plates. The surfaces of the tanks adjoin each other very tightly. Small membrane vesicles bud off from the peripheral part.

Human cells have one, rarely a couple of stacks, and plant cells can contain several such formations. The collection of cisterns (one stack) together with the surrounding vesicles is called dictyosome. Several dictyosomes can communicate with each other to form a network.

Polarity- the presence of the cis-side directed to the EPS and the nucleus, where the vesicles merge, and the trans-side, directed to the cell membrane (this feature is well traced in the cells of secreting organs).

Asymmetry- the side located closer to the cell nucleus (proximal pole) contains "immature" proteins, vesicles detached from the EPS are constantly attached to it, the trans-side (distal, mature pole) contains already modified proteins.

When the lamellar complex is destroyed by foreign agents, the Golgi apparatus is divided into separate parts, but its main functions are preserved. After the resumption of the system of microtubules, which were chaotically scattered in the cytoplasm, parts of the apparatus are collected, and again turn into a normally functioning lamellar complex. Physiological separation also occurs under normal conditions of cell life, during indirect division.

EPS and Golgi complex

Is EPS a part of the Golgi complex?

Definitely not. The endoplasmic reticulum is an independent membrane organelle, which is built from a system of closed tubules, cisterns, formed by a continuous membrane. The main function is the synthesis of proteins using ribosomes located on the surface of the granular EPS.

There are a number of similarities between EPS and the Golgi apparatus:

• These are intracellular formations delimited from the cytoplasm by a membrane;
• separate membrane vesicles that are filled with organic synthesis products;
• together form a single synthesizing system;
• in secreting cells have the largest size and high level development.

How the walls are formed endoplasmic reticulum and the Golgi complex?

The walls of the EPS and the Golgi apparatus are presented in the form of a single-layer membrane. These organelles, together with lysosomes, peroxisomes, and mitochondria, are combined into a group of membrane organelles.

What happens in the Golgi complex with hormones and enzymes?

The endoplasmic reticulum is responsible for the synthesis of hormones; hormonal substances are produced on the surface of its membrane. Synthesized hormones enter the Golgi complex, here they accumulate, then they are processed and excreted. Therefore, in the cells of endocrine organs, there are complexes large sizes(up to 10 microns).

Functions of the Golgi complex

Proteolysis protein substances, which leads to the activation of proteins, so proinsulin is converted into insulin.

Provides transport of EPS synthesis products from the cell.

The most important function of the Golgi complex is considered to be the excretion of synthesis products from the cell, therefore it is also called the transport apparatus of the cell.

Synthesis of polysaccharides, such as pectin, hemicellulose, which are part of the membranes of plant cells, the formation of glycosaminoglycans, one of the components of the intercellular fluid.

In the tanks of the plate complex goes maturation of protein substances required for secretion, transmembrane proteins of the cell membrane, lysosomal enzymes, etc. During maturation, proteins gradually move through the organoid sections, in which their formation is completed and glycosylation and phosphorylation occur.

Formation of lipoprotein substances. Synthesis and accumulation of mucous substances (mucin). Formation of glycolipids, which are part of the membrane glycocalyx.

It transfers proteins in three directions: to lysosomes (the transfer is controlled by an enzyme - mannose-6-phosphate), to membranes or the intracellular environment, and to the intercellular space.

Together with grainy EPS forms lysosomes, by fusion of budded vesicles with autolytic enzymes.

Exocytic transfer- the vesicle, approaching the membrane, is embedded in it and leaves its contents with outside cells.

Summary table of the functions of the Golgi complex

Structural unit	Functions
Cis-tank	Capture of proteins synthesized by EPS, membrane lipids
Median cisterns	Post-translational modifications associated with the transfer of acetylglucosamine.
Trans cistern	Glycosylation is completed, the addition of galactose and sialic acid is completed, and substances are sorted for further transport from the cell.
Bubbles	They are responsible for the transfer of lipids and proteins into the Golgi apparatus and between cisterns, as well as for the excretion of synthesis products.

The Golgi apparatus is an important organelle that is present in almost every one. Perhaps the only cells that lack this complex are the erythrocytes of vertebrates. The functions of this structure are very diverse. It is in the tanks of the apparatus that all the compounds produced by the cell accumulate, after which they are further sorted, modified, redistributed and transported.

Despite the fact that the Golgi apparatus was discovered back in 1897, some of its functions are actively studied to this day. Let's consider in more detail the features of its structure and functioning.

Golgi apparatus: structure

This organelle is a collection of membrane cisterns that are closely adjacent to each other, resembling a stack. The structural and functional unit here is considered to be the dictyosome.

The dictyosome is a separate, independent part the Golgi apparatus, which consists of 3 - 8 closely adjacent tanks. The stack of these membrane cisterns is surrounded by a system of small vacuoles and vesicles - this is how the transport of substances is carried out, as well as the connection of dictyosomes between themselves and other cellular structures. As a rule, they have only one dictyosome, while in plant structures there can be many of them.

In a dictyosome, it is customary to separate two ends - the cis and trans sides. The cis side faces the nucleus and the granular endoplasmic reticulum. Synthesized proteins and other compounds are transported here in the form of membrane vesicles. At this end of the dictyosome, new cisterns are constantly being formed.

The trans side is facing towards It is usually slightly wider. This includes compounds that have already passed all the stages of modification. Small vacuoles and vesicles constantly detach from the lower cistern, which transport substances to the desired cell organelles.

Golgi apparatus: functions

As already mentioned, the functions of the organelle are very diverse.

• This is where the newly synthesized protein molecules are modified. In most cases, a carbohydrate, sulfate or phosphorus radical is attached to a protein molecule. Thus, the Golgi apparatus is responsible for the formation of enzymes and proteins of lysosomes by protein.
• The Golgi apparatus is responsible for the transport of modified proteins to specific areas of the cell. From the trans side, small bubbles are constantly separated, which contain the ready-made proteins.
• This is where the formation and transport of all lysosomal enzymes takes place.
• In the cavities of the cisterns, lipids accumulate, and later the formation of lipoproteins - a complex of protein and lipid molecules.
• The Golgi apparatus of a plant cell is responsible for the synthesis of polysaccharides, which are then used to form a plant, as well as mucus, pectins, hemicellulose and waxes.
• After the division of the plant cell, the Golgi complex takes part in the formation of the cell plate.
• In the sperm, this organelle takes part in the formation of enzymes of the acrosome, with the help of which the oocyte membranes are destroyed during fertilization.
• In the cells of the protozoa, the Golgi complex is responsible for the formation of which regulate

Of course, this is not a complete list of all functions performed. Modern scientists are still conducting a wide variety of studies using Newest technologies... It is likely that the list of functions of the Golgi complex will grow significantly in the next few years. But today we can say with certainty that this organelle supports the normal vital activity of both the cell and the whole organism as a whole.

Golgi complex is a stack of disc-shaped membrane sacs (cisterns), somewhat expanded closer to the edges, and the associated Golgi vesicle system. A number of separate stacks (dictyosomes) are found in plant cells; animal cells often contain one large or several stacks connected by tubes.

1. Accumulates and removes organic substances synthesized in the endoplasmic reticulum

2. Forms lysosomes

3. Formation of carbohydrate components of the glycocalyx - mainly glycolipids.

Lysosomes are an integral part of the composition of the cell. They are a type of vesicle. These cellular assistants, being part of the vacuome, are covered with a membrane and filled with hydrolytic enzymes. The importance of the existence of lysosomes inside the cell is provided by the secretory function, which is necessary in the process of phagocytosis and autophagocytosis.

Perform digestive function- digest food particles and remove dead organelles.

Primary lysosomes- these are small membrane vesicles, which have a diameter of about one hundred nm, filled with a homogeneous finely dispersed content, which is a set of hydrolytic enzymes. There are about forty enzymes in lysosomes.

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 the primary lysosomes, and the material for digestion is supplied by the endocytic (pinocytic) vacuole.

19. Eps, its varieties, role in the processes of synthesis of substances.

Endoplasmic reticulum in different cells it can be presented in the form of flattened cisterns, tubules or separate vesicles. The wall of these formations consists of a bilipid membrane and some proteins included in it and delimits the internal environment of the endoplasmic reticulum from the hyaloplasm.

There are two types of endoplasmic reticulum:

grainy (granular or rough);

non-grained or smooth.

The outer surface of the membranes of the granular endoplasmic reticulum contains attached ribosomes. In the cytoplasm, there can be both types of the endoplasmic reticulum, but usually one form predominates, which determines the functional specificity of the cell. It should be remembered that these two varieties are not independent forms of the endoplasmic reticulum, since it is possible to trace the transition of the granular endoplasmic reticulum to the smooth one and vice versa.

Functions of the granular endoplasmic reticulum:

synthesis of proteins intended for removal from the cell ("for export");

separation (segregation) of the synthesized product from the hyaloplasm;

condensation and modification of the synthesized protein;

transport of synthesized products to the tanks of the lamellar complex or directly from the cell;

synthesis of bilipid membranes.

The smooth endoplasmic reticulum is represented by cisterns, wider canals and individual vesicles, on the outer surface of which there are no ribosomes.

Functions of the smooth endoplasmic reticulum:

participation in the synthesis of glycogen;

synthesis of lipids;

detoxification function - neutralization of toxic substances by combining them with other substances.

The lamellar Golgi complex (mesh apparatus) is represented by an accumulation of flattened cisterns and small vesicles bounded by a bilipid membrane. The lamellar complex is subdivided into subunits - dictyosomes. Each dictyosome is a stack of flattened cisterns, along the periphery of which small vesicles are localized. At the same time, in each flattened cistern, the peripheral part is somewhat widened, and the central one is narrowed.

The endoplasmic reticulum, or endoplasmic reticulum, is a system of tubules and cavities that permeate the cytoplasm of a cell. EPS is formed by a membrane that has the same structure as the plasma membrane. The tubules and cavities of the EPS can occupy up to 50% of the cell volume and do not break off anywhere and do not open into the cytoplasm. Distinguish between smooth and rough (granular) EPS. On rough EPS there are many ribosomes. This is where most proteins are synthesized. The synthesis of carbohydrates and lipids occurs on the surface of the smooth EPS.

Functions of the granular endoplasmic reticulum:

• · Synthesis of proteins intended for removal from the cell ("for export");
• · Separation (segregation) of the synthesized product from the hyaloplasm;
• · Condensation and modification of synthesized protein;
• · Transport of synthesized products to the tanks of the lamellar complex or directly from the cell;
• · Synthesis of bilipid membranes.

The smooth endoplasmic reticulum is represented by cisterns, wider canals and individual vesicles, on outer surface which lack ribosomes.

Functions of the smooth endoplasmic reticulum:

• · Participation in the synthesis of glycogen;
• · Lipid synthesis;
• · Detoxification function - neutralization of toxic substances by combining them with other substances.

Golgi complex (apparatus).

The system of intracellular cisterns in which substances synthesized by the cell accumulate is called the Golgi complex (apparatus). Here, these substances undergo further biochemical transformations, are packed into membrane vesicles and are transferred to those places of the cytoplasm where they are needed, or they are transported to the cell membrane and go outside the cell (Fig. 32). The Golgi complex is built of membranes and is located next to the EPS, but does not communicate with its channels. Therefore, all substances synthesized on the EPS membranes are transferred to the Golgi complex inside the membrane vesicles that bud off from the EPS and then merge with the Golgi complex. Another important function of the Golgi complex is the assembly of cell membranes. The substances that make up the membranes (proteins, lipids) enter the Golgi complex from the EPS, in the cavities of the Golgi complex membrane sections are collected from which special membrane vesicles are made. They move along the cytoplasm to those places of the cell where it is required to complete the membrane.

Functions of the Golgi apparatus:

• · Sorting, accumulation and removal of secretory products;
• · Accumulation of lipid molecules and the formation of lipoproteins;
• · The formation of lysosomes;
• · Synthesis of polysaccharides for the formation of glycoproteins, waxes, gums, mucus, matrix substances of plant cell walls;
• · Formation of the cell plate after nuclear division in plant cells;
• · The formation of contractile protozoan vacuoles.

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 one-membrane bubbles (Golgi bubbles) is associated with them. Each stack usually consists of 4-6 "cisterns", 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, it is often near the cell center).

Golgi complex

Left - in a cage, among other organelles.

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

All substances synthesized on EPS membranes carried over to Golgi complex v membrane vesicles, which branch off from the EPS and then merge with the Golgi complex. The incoming organic matter from EPS undergoes further biochemical transformations, accumulates, and is packed into membrane vesicles and delivered to the places in the cage where they are needed. They are involved in the completion cell membrane or stand out outward ( 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, the synthesis of polysaccharides takes place, their complexation with protein molecules.

2) Secretory - the formation of finished secretory products that are removed outside the cell by exocytosis.

3) Renewal of cell membranes, including areas of the plasma membrane, as well as replacement of plasma membrane defects in the process of cell secretory activity.

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

Lysosomal enzymes are synthesized on a rough EPS, transferred 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. Degradation of substances absorbed as a result of phagocytosis and pinocytosis. Biopolymers are broken down to monomers, which enter the cell and are used for its needs. For example, they can be used to synthesize new organic substances, or they can be further degraded to generate energy.

2. Destroy old, damaged, excess organelles. The destruction of organelles can also occur during cell starvation.

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

Autolysis - this is self-destruction cells resulting from the release of contents lysosomes inside the cell. Thanks to this, lysosomes are jokingly called "Instruments of suicide." Autolysis is a normal phenomenon of ontogenesis, it can spread both to individual cells and to the entire tissue or organ, as it happens during the resorption of the tadpole's tail during metamorphosis, i.e., when the tadpole turns into a frog

Endoplasmic reticulum, Golgi apparatus and lysosomesform a single vacuolar system of the cell, individual elements which can transform into each other during restructuring and changing the function of membranes.

Mitochondria

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

In shape, mitochondria can be rod-shaped, rounded, spiral, cupped, 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.

The mitochondrion is limited two membranes ... The outer membrane of mitochondria is smooth, the inner membrane forms numerous folds - crista. Crystals increase the surface area of ​​the inner membrane. The number of cristae in mitochondria can vary depending on the cell's energy requirements. It is on the inner membrane that numerous enzyme complexes are concentrated that participate in the synthesis of adenosine triphosphate (ATP). Here, the energy of chemical bonds is converted into energy-rich (high-energy) ATP bonds ... Besides, in mitochondria, the breakdown of fatty acids and carbohydrates takes place 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. It is interesting that 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, which contains up to 2% of the DNA of the cell itself).

Mitochondrial functions:

1. Conversion of the energy of chemical bonds into high-energy ATP bonds (mitochondria are the "energy stations" of the cell).

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

Ribosomes

Ribosome structure:
1 - large subunit; 2 - small subunit.

Ribosomes - non-membrane organelles, about 20 nm in diameter. Ribosomes are composed of two fragments - a large and a small subunit. Chemical composition ribosomes - proteins and rRNA. RRNA molecules make up 50–63% of the ribosome mass 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 one mRNA molecule.

Subunits of ribosomes are formed in the nucleolus. Having passed through the pores in the nuclear envelope, ribosomes enter the membranes of the endoplasmic reticulum (EPS).

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

Cytoskeleton

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 unable to contract and can be destroyed by colchicine.

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

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

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

· Provide movement of organelles;

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

Cell center

The cell center is an organoid consisting of 2 small granule centrioles and a radiant sphere around them - the centrosphere. The centriole is a cylindrical body 0.3-0.5 microns long and about 0.15 microns in diameter. The walls of the cylinder consist of 9 parallel tubes. The centrioles are arranged in pairs at right angles to each other. The active role of the cell center is found 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 an even distribution of genetic material between daughter cells.

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

Functions:

1. Ensuring a 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

Organoids of movement include cilia, as well as flagella. These are miniature hair-like outgrowths. 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, which have only 10-20 microns, are called cilia ... When the microtubules slide, the cilia and flagella are able to vibrate, causing the cell itself to move. The cytoplasm may contain contractile fibrils called myofibrils. Myofibrils are usually located in myocytes - cells muscle tissue as well as in the cells of the heart. They are composed of smaller fibers (protofibrils).

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

Functions:

Specific

Core. Chromosomes