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As a rule, a eukaryotic cell has one nucleus, but there are binuclear (ciliates) and multinucleated cells (opaline). Some highly specialized cells lose their nucleus again (erythrocytes of mammals, sieve tubes of angiosperms).
The shape of the nucleus is spherical, elliptical, less often lobed, bean-shaped, etc. The diameter of the nucleus is usually from 3 to 10 microns.

Core structure:

1 - outer membrane; 2 - inner membrane; 3 - pores; 4 - nucleolus; 5 - heterochromatin; 6 - euchromatin.

The nucleus is delimited from the cytoplasm by two membranes (each of them has a typical structure). Between the membranes there is a narrow gap filled with a semi-liquid substance. In some places, the membranes merge with each other, forming pores (3) through which the exchange of substances between the nucleus and the cytoplasm takes place. The outer nuclear (1) membrane from the side facing the cytoplasm is covered with ribosomes, which give it roughness, the inner (2) membrane is smooth. Nuclear membranes are part of the cell membrane system: the outgrowths of the outer nuclear membrane are connected to the channels of the endoplasmic reticulum, forming unified system communicating channels.

Karyoplasm (nuclear juice, nucleoplasm) is the inner content of the nucleus, in which chromatin and one or more nucleoli are located. Nuclear juice contains various proteins (including nuclear enzymes), free nucleotides.

The nucleolus (4) is a rounded dense body immersed in nuclear juice. The number of nucleoli depends on functional state kernels and varies from 1 to 7 or more. The nucleoli are found only in non-dividing nuclei; during mitosis, they disappear. The nucleolus is formed on certain parts of the chromosomes that carry information about the structure of rRNA. Such regions are called the nucleolar organizer and contain numerous copies of the genes encoding rRNA. From rRNA and proteins coming from the cytoplasm, ribosome subunits are formed. Thus, the nucleolus is an accumulation of rRNA and ribosomal subunits at different stages of their formation.

Chromatin - internal nucleoprotein structures of the nucleus, stained with some dyes and differing in shape from the nucleolus. Chromatin is in the form of lumps, granules and filaments. The chemical composition of chromatin: 1) DNA (30–45%), 2) histone proteins (30–50%), 3) non-histone proteins (4–33%), therefore, chromatin is a deoxyribonucleoprotein complex (DNP). Depending on the functional state of chromatin, they are distinguished: heterochromatin (5) and euchromatin (6). Euchromatin is genetically active, heterochromatin is genetically inactive regions of chromatin. Euchromatin under light microscopy is indistinguishable, weakly stained and represents decondensed (despiralized, untwisted) areas of chromatin. Heterochromatin under a light microscope looks like lumps or granules, intensely stains and represents condensed (spiralized, compacted) areas of chromatin. Chromatin is a form of the existence of genetic material in interphase cells. During cell division (mitosis, meiosis), chromatin is converted into chromosomes.

All living things are composed of cells - elementary and fundamental particles. What is the difference between animals and plants, what they are made of and what they are like - all this can be learned from this article.

All living things (people, animals, plants) are extremely complex in structure, but they are united by one fundamental part - the cell.

It is an independent biosystem that has the main features and properties of a living organism, i.e. it can grow, change, share, move and adapt to its environment. In addition, cells also possess:

• special structure;
• ordered structures;
• metabolism;
• a set of certain functions.

There is a whole science dealing with the study of these particles - cytology. Its task is to study not only single-celled organisms such as bacteria and viruses, but also the structural units of large and complex objects such as humans, plants and animals.

Their general organization is extremely similar - they all have a nucleus, as well as a certain set of organelles.

Cells and their functions are diverse in their parameters. They have different shapes and sizes, each with its own work in the body. But they also have common features - the chemical structure and the organizational principle of structures. Each molecule contains certain organelles or organelles - permanent structures or their constituent parts.

Good to know! There are only 220 billion cells in the human body, of which about 20 billion are permanent and 200 billion are replaceable.

Not everything has been studied, many questions regarding the structure and functions of these particles remain open and discussions about them continue. For example, do lysosomes also belong to organelles or not?

Classification

Cells are classified according to the type of their components. As already mentioned, each of them contains certain organelles inside - functional parts, and classifies the structural unit depending on these parts. Allocate:

1. Non-membranous - there are no organelles inside that would be surrounded by a film.
2. Membrane - organelles are present inside, which are surrounded by two or more films (for example, mitochondria).

Membranes, in turn, are subdivided into:

• one-membrane - cell organelles and their internal particles are separated by one biological film. These include the Golgi complex, etc .;
• two membrane organelles - in these parts, the nucleus is hidden behind two films.

The membrane helps to keep the organelle from the cytoplasm and to give it a shape, while they can be different in their composition due to the different amount of proteins. In addition to them, a (wall) is also found in plant molecules, which is located on the outer side of the unit, which performs a supporting function.

Organelles

Organoids are permanent components that reside in the cell's plasma, thanks to which it can exist, be whole and fulfill its nature-inherent responsibilities. These particles include:

• golgi complex;
• structures that form the cytoskeleton;
• ribosomes;
• lysosomes.

But the nucleus is not an organelle, just like the membranes with cilia and flagella.

Organoids of an animal cell also contain microfibrils, and organelles of a plant cell contain plastids.

The composition of organelles itself is excellent, i.e. each has its own, it is due to the type of the structural unit itself and its role in the body. Cytology divides units on this basis into:

1. Prokaryotes are cells without a nucleus. This type includes all kinds of viruses, bacteria and simple algae. They contain only cytoplasm and one chromosome (DNA molecule).
2. Eukaryotes are cells with a nucleus that consists of nucleoproteins (protein + DNA) and other organelles. All major living organisms belong to eukaryotes.

All together, the cellular structures provide effective and continuous activity, thanks to the interconnection between its components, the structural particle of the body gets the opportunity to develop. The structure and function of cell organelles should be considered separately.

Structure

Each individual organelle has its own structure, contributing to the effective performance of certain functions of the structural unit. The table below contains the organelles of the plant particle and their structure.

Important!All these organelles are contained in the cytoplasm - a semi-liquid granular medium.

Thus, each individual organelle has an individual structure, which ensures the implementation of its main functions.

Functions

Every single particle inside does its job. Their relationship ensures the vital activity of not only this structural unit, but the whole organism as a whole.

Everything in this world consists of different particles that make up a single picture, just like a living cell consists of organelles. The "unit of life" is covered with a protective barrier - a membrane that delimits external world from internal content. The structure of cell organelles is a whole system that has to be understood.

Eukaryotes and prokaryotes

In nature, there is a huge number of cell types, only in the human body there are more than 200 of them, but only 2 types of cellular organization are known - these are eukaryotic and prokaryotic. Both of these types arose through evolution. Eukaryotes and prokaryotes have a cell membrane, but that's where the similarities end.

Cells of a prokaryotic species have small size and cannot boast of a well-developed membrane. The main difference is the lack of a core. In some cases, plasmids are present, which are a ring of DNA molecules. Organoids in such cells are practically absent - only ribosomes are found. Prokaryotes include bacteria and archaea. Moners - this is what was previously called unicellular bacteria that do not have a nucleus. Today this term has fallen out of use.

The eukaryotic-type cell is much larger than prokaryotes and includes a structure called organelles. Unlike its simplest "relative", the eukaryotic cell has linear DNA, which is located in the nucleus. Another interesting difference between these two species - mitochondria and plastids, which are located inside the eukaryotic cell, strikingly resemble bacteria in their structure and activity. Scientists have put forward the assumption that these organelles are descendants of prokaryotes, in other words, earlier prokaryotes entered into symbiosis with eukaryotes.

"Device" eukaryotic cell

Cell organelles are small parts of a cell that perform important functions, such as storing genetic information, synthesis, division, and others.

Organelles include:

• Cell membrane;
• Golgi complex;
• Ribosomes;
• Microfilaments;
• Chromosomes;
• Mitochondria;
• Endoplasmic reticulum;
• Microtubules;
• Lysosomes.

The structure of organelles of cells of animals, plants and humans is the same, but each of them has its own characteristics. Microfibrils and centrioles are characteristic of animal cells, and plastids for plant cells. The table of the structure of cell organelles will help to gather information together.

Some scientists attribute the cell nucleus to its organelles. The kernel is located in the center and has an oval or round shape. Its porous shell consists of 2 membranes. The shell has two phases - interphase and fission.

The cell nucleus has two functions - storage of genetic information and protein synthesis. Thus, the core is not only a "repository", but also a place where material is reproduced and functions.

Table: structure of cell organelles

Cell organelles - video

It is 2-membered, porous. The outer one passes into the EPS membrane, which is characteristic of all eukaryotic cells. The pores have a certain structure - the result of the fusion of the outer and inner nuclear membranes.

In a non-dividing cell, chromatin is a fine-grained, filamentous structure. They consist of DNA molecules and a protein nucleoprotein sheath. When the cell divides, the chromatin structures coiled tightly to form chromosomes. Each consists of 2 chromatids, in chromatids condensation of chromatin occurs, which includes special proteins - histones .

Chromatids after nuclear division diverge to the poles and chromosomes becomemonochromatid ... By the beginning of the next division, each chromosome completes the 2nd chromatid. The chromosome has a primary constriction; the centromere is located on it. It divides the chromosome into 2 arms:

Metacentric - have a centromere in the middle

Submetacentric - have one large, one small shoulder

Acrocentric - have a centromere almost at the end of the chromosome.

Satellite

The nucleolar chromosomes may have a secondary constriction.

The spherical body, which is not an independent structure, resembles a ball of thread, does not have a membrane. It consists of a protein, r-RNA, is formed on the secondary constriction of the nucleolar chromosome, they are called nucleolar organizers, it breaks down during cell division.

Semi-liquid substance in the formcolloidal solution of proteins, nucleic acids, carbohydrates, mineral salts, acidic

A thin ultramicroscopic film (about 10 nm), which is a liquid-mosaic model, which consists of bimolecular lipid layer, the integrity of which is interrupted by protein molecules or pores. Squirrels are mosaic:

AND)submerged (semi-integral) -partly included in the lipid layer

B)piercing(integral) - penetrate through 2 layers of lipids

IN)superficial (near-membrane or peripheral) - are located on the surface of the lipid layer. Proteins form enzymatic systems, and lipids are composed of polar heads and non-polar water-repellent tails. On the surface of animal cells there is a layer of polysaccharides - glycocalyx. In plant and fungal cells, the membrane is surrounded by a cell wall composed mainly of cellulose or chitin

Ultramicroscopic system of membranes, tubules, cisterns and vesicles. It has a universal structure, it can start from the outer cell membrane to the outer nuclear membrane. It unites the membrane chain into a single whole, it contains enzymatic systems or ribosomes, in this regard, there are 2 types of EPS:

AND)agranular or smooth - it contains enzymatic systems, it prevails in seed cells, rich in storage substances

B)granular or rough - carries ribosomes, which form polysomes during synthesis

It is a microscopic structure. In plant cells, it is visible only under a microscope, and is a stack of flat cisterns (from 5 to 10), small tubes and bubbles extend along the edges.

There are 2 poles:

AND)building

B)secretory

The number of dictyosomes reaches 20

Microscopic or submicroscopic organelles in the form of small bubbles with a diameter of 0.5 μm. Their number depends on the vital activity of the cell and its physiological state. Lysosomes contain lysing and dissolving enzymes synthesized on ribosomes, then they enter the EPS, and from there into the Golgi complex, where they separate in the form of vesicles with enzymes

AND)primary - formed in the Golgi apparatus

B)secondary - formed as a result of phagocytosis

Structures characteristic of a plant cell,

this issingle membrane organelles, having a pronouncedtonoplast ... Inside there is a cell juice containing minerals, enzymes, vitamins. In young cells, vacuoles are small and there are many of them, while in old cells they merge into one large one and displace the nucleus to the periphery. The content of the vacuole - cell juice - is a weakly acidic (pH 2-5) aqueous solution of various organic and inorganic substances (in immature fruits or in ripe lemon fruits, the cell juice has a strongly acidic reaction). In terms of chemical composition and consistency, cell sap differs significantly from protoplast. These differences are associated with the selective permeability of the tonoplast, which performs the barrier function. Most of the organic substances contained in the cell sap belong to the group ergasticmetabolic products of the protoplast. Depending on the needs of the cell, they can accumulate in vacuoles in significant quantities or disappear completely. The most common are various carbohydrates that play the role of reserve energy substances, as well as organic acids. Seed vacuoles often contain protein proteins. Plant vacuoles often serve as a place of concentration of various secondary metabolites - polyphenolic connections:flavonoids, anthocyanins, tannidsand nitrogen-containing substances -alkaloids. Many inorganic compounds are also dissolved in the cell sap.In animal cells, the content of vacuoles depends on their species. Either these are vital enzymes - digestive vacuoles, or these are substances designed to remove excess water, salt - contractile vacuole

Organelle for most plant and animal cells, microscopic organelletwo-membrane buildings.

The outer membrane is smooth, the inner one forms various forms of outgrowths, in plants - tube-like, in animals - crista ... In shape, mitochondria resemble elongated structures. The internal content of the matrix or semi-liquid substance contains proteins, lipids, Ca M salts g, vitamins, as well as DNA, RNA and ribosomes.

On the surface of the cristae, there may be enzymes involved in synthesis of ATP... Mitochondria can divide, live for about 10 days, and break down

Are characteristiconly for plant eukaryotic cells, have a round or oval shape, are formed from proplastids and multiply by division. They can pass from one species to another, are semi-autonomous organelles, having their own genetic apparatus of DNA and RNA, ribosomes and proteins

Double membrane organelles complex structure containingchlorophyll, In algae, chlorophyll carriers arechromatophores ... Plants have a biconvex shape. The cells contain up to 1000 chloroplasts, it is covered with a smooth outer membrane, and the inner one forms plastids in the cavity thylakoids. Disciform thylakoids formgrains , and tubular thylakoids -lamellae ... The number of grains can reach 40-60. The grains resemble a stack of coins. The stroma (matrix) contain proteins, lipids, enzymes, ATP, as well as p-DNA, RNA and ribosomes. The grains contain chlorophyll grains, as well as carotenoids. Reproduce by division.

They various shapes: filiform, rhombic, triangular, acicular, crescent, lamellar, spherical. During the transition of chloroplasts to chromoplasts, carotenoids crystallize as chlorophyll breaks down and break the plastids. Carotenoids can be dissolved in lipid globules or heated in protein fibrils. The form of carotenoids is typical for every plant species, they have a two-membrane structure, and the inner membrane is represented by single thylakoids.

Colorless small plastids, rounded, with a very simple structure, formed from proplastids, have a double membrane, the inner one forms 2-3 protrusions in stroma and the outer membrane is smooth. All plastids are capable of fission. The stroma contains DNA, ribosomes, enzymes that carry out synthesis and hydrolysis.

An ultramicroscopic organelle, which is a complex-shaped particle, consisting of 2 unequal subunits - large and small.

There are 2 types of ribosomes:

Eukaryotic - sedimentation coefficient

80 S- whole, 40S - small, 60S - large.

Prokaryotic - 70 S - whole,

30 S- small, 50S- large.

In ribosomes located in mitochondria and chloroplasts, the sedimentation coefficient is 70S... Ribosomes are formed in the nucleoli in the form of subunits, then pass into the cytoplasm, they can be round or mushroom in shape, they do not have a membrane structure, they consist of protein and r-RNA. r-RNA contains about 63% of the mass of ribosomes, forming its framework. In the process of protein synthesis, ribosomes are able to combine on i-RNA into chains - polysomes. The number of polysomes indicates the intensity of protein biosynthesis, ribosomes can be located in the granular EPS and in the cytoplasm

Ultramicroscopic organelle of non-membrane structure. Consists of 2 centrioles, located perpendicular to each other, and surrounded by cytoplasm - the centrosphere.

Each centriole has a cylindrical shape, its walls are formed by 9 triplets of tubes. In the middle there is a homogeneous substance, the centrosome is located near the nucleus, during cell division it is divided into 2 parts.

FORMULA of microtubules:

(9 *3)+2 = 29

These are spherical bodies with a diameter of 1 micron. Inherent in all plants, they are a 2-layer phospholipid ball, to which protein molecules are attached, as a result a third protein layer appears.

Complex of ribosomes, RNA and protein. They are inherent only in plant cells.

Single outgrowths of the cell cytoplasm. Typical for the simplest flagellates

(euglena green, lamblia, trypanosomes)

Top covered with plasmalemma, consist of microtubules (formula: 9 * 2 + 2).

The main contractile protein -TUBULIN (human sperm, unicellular algae

- chlamydomonas, Volvox),

prokaryotes - proteinflagellin.

Short numerous outgrowths of the cytoplasm protruding from the cell. They cover the plasmalemma. They include tubulin

Outgrowths of the cytoplasm anywhere in the cell, formed by dragging the cytoplasm. Typical for leukocytes, amoeba, arcella, diflugia - rhizomes. Have a changeable shape

The musculoskeletal system of the cell. Organelles are located in the cytoplasm from the nuclear membrane to the plasmalemma. The main ones are microtubules and microfiloments.

Hollow cylinders, the walls of which are formed by the protein tubulin

Very thin and long cylinders or tubules containing active proteins: ACTIN and MYOSIN. In the presence of ATP, they combine into long chains. Microfiloids are located under the eukaryotic plasma membrane

Peroxisome (lat.peroxysoma ) - obligatory organelleeukaryoticcells, limited by a membrane containing a large amountenzymescatalyzingredox reactions (d-amino acid oxidase, urate oxidase andcatalase). Has a size from 0.2 to 1.5μm, separated from the cytoplasm by one membrane. This type of oxidative reaction is especially important in cellsliver andkidney, whose peroxisomes neutralize many toxic substances that enter the bloodstream. Almost half of the ethanol entering the human body is oxidized to acetaldehyde in this manner. In addition, the reaction is important for the detoxification of the cell from hydrogen peroxide itself. New peroxisomes are formed most often as a result of division of the preceding ones, like mitochondria andchloroplasts... They, however, can form andde novo ofendoplasmic reticulumdo not containDNA andribosome, therefore, the previously stated assumptions about theirendosymbiotic origin are unfounded.

All enzymes found in the peroxisome must be synthesized on the ribosomes outside of it. To transfer them fromcytosol peroxisome membranes inside the organelle have a selective transport system. Since hydrogen peroxide is a toxic substance, it is degraded by peroxidase. The reactions of formation and cleavage of hydrogen peroxide are involved in many metabolic cycles, especially those actively occurring in the liver and kidneys. Therefore, in the cells of these organs, the number of peroxisomes reaches 70-100.