Nucleus - what is it in biology? The meaning of the word core What does core mean.

home

CCTV

Core I Core

cellular, an obligatory, along with the cytoplasm, component of the cell in protozoa, multicellular animals and plants, containing chromosomes and the products of their activity. Based on the presence or absence of nitrogen in cells, all organisms are divided into eukaryotes (See Eukaryotes) and prokaryotes (See Prokaryotes). The latter do not have a formed ego (its shell is missing), although deoxyribonucleic acid (DNA) is present. The main part of the cell's hereditary information is stored in the nucleus; genes contained in chromosomes play main role in the transmission of hereditary characteristics in a number of cells and organisms. Ya is in constant and close interaction with the cytoplasm; it synthesizes intermediary molecules that transfer genetic information to the centers of protein synthesis in the cytoplasm. Thus, the ego controls the synthesis of all proteins and, through them, all physiological processes in the cell. Therefore, experimentally obtained nuclear-free cells and cell fragments always die; when transplanted into such cells, their viability is restored. I. was first observed by the Czech scientist J. Purkynė (1825) in a chicken egg; in plant cells it was described by the English scientist R. Brown (1831-33), and in animal cells by the German scientist T. Schwann (1838-39).

Usually there is only one nucleus in a cell, it is located near its center, and has the form of a spherical or ellipsoidal bubble ( figures 1-3, 5, 6 ). Less often Y. is incorrect ( figure 4 ) or complex shapes (for example, Ya. leukocytes, Macronucleus s ciliates). Bi- and multinucleated cells are not uncommon, usually formed by nuclear division without division of the cytoplasm or by the fusion of several mononuclear cells (the so-called symplasts, for example, striated muscle fibers). Ya sizes vary from Core 1 µm(in some protozoa) up to Core 1 mm(some eggs).

The nucleus is separated from the cytoplasm by the nuclear envelope (NE), consisting of 2 parallel lipoprotein membranes 7-8 thick nm, between which there is a narrow perinuclear space. Nuclear weapons are permeated with pores with a diameter of 60-100 nm, at the edges of which the outer membrane of the nuclear weapon passes into the inner one. The frequency of pores varies in different cells: from units to 100-200 per 1 µm 2 surface I. Along the edge of the pore there is a ring dense material- the so-called annulus. In the lumen of the pore there is often a central granule with a diameter of 15-20 nm, connected to the annulus by radial fibrils. Together with the pores, these structures constitute a pore complex, which apparently regulates the passage of macromolecules through the nuclear system (for example, the entry of protein molecules into the nuclear system, the exit of ribonucleoprotein particles from the nuclear system, etc.). The outer membrane of the NE in places passes into the membranes of the endoplasmic reticulum (See Endoplasmic reticulum); it usually carries protein-synthesizing particles - ribosomes . The internal membrane of the nucleus sometimes forms invaginations into the depths of the nucleus. The contents of the nucleus are represented by nuclear juice (karyolymph, karyoplasm) and formed elements immersed in it - chromatin, nucleoli, etc. Chromatin is more or less loosened in the non-dividing nucleus the material of chromosomes, the DNA complex with proteins - the so-called deoxyribonucleoprotein (DNP). It is detected using the Feulgen color reaction for DNA ( figures 1 and 8 ). During cell division (see Mitosis), all chromatin is condensed into chromosomes; at the end of mitosis, most of the chromosome sections are loosened again; these regions (called euchromatin) contain mostly unique (non-repeating) genes. Other regions of the chromosomes remain dense (so-called heterochromatin); they contain mostly repeating DNA sequences. In a non-dividing cell, most of the euchromatin is represented by a loose network of DNP fibrils with a thickness of 10 - 30 nm, heterochromatin - dense clumps (chromocenters), in which the same fibrils are tightly packed. Some euchromatin can also transform into a compact state; such euchromatin is considered inactive in relation to RNA synthesis. Chromocenters usually border the nuclear center or nucleolus. There is evidence that DNP fibrils are anchored on the inner membrane of the nuclear reactor.

In a non-dividing cell, DNA synthesis (replication) occurs, which is studied by recording DNA precursors (usually thymidine) included in the cell, labeled with radioactive isotopes. It has been shown that along the length of chromatin fibrils there are many sections (so-called replicons), each with its own starting point for DNA synthesis, from which replication spreads in both directions. Due to DNA replication, the chromosomes themselves double.

In nuclear chromatin, the genetic information encoded in DNA is read through the synthesis of matrix, or information, RNA molecules on DNA (see. Transcription), as well as molecules of other types of RNA involved in protein synthesis. Special regions of chromosomes (and, accordingly, chromatin) contain repeating genes that encode ribosomal RNA molecules; in these places, cells rich in ribonucleoproteins (RNP) are formed nucleoli, the main function of which is the synthesis of RNA, which is part of the ribosomes. Along with the components of the nucleolus, there are other types of RNA particles in the nucleus. These include perichromatin fibrils with a thickness of 3-5 nm and perichromatin granules (PG) with a diameter of 40-50 nm, located at the boundaries of zones of loose and compact chromatin. Both of them probably contain messenger RNA in combination with proteins, and PGs correspond to its inactive form; release of PG from the cell into the cytoplasm through the pores of the cell was observed. There are also interchromatin granules (20-25 nm), and sometimes thick (40-60 nm) RNP threads twisted into balls. In the nuclei of amoebas there are RNP threads twisted into spirals (30-35 nm x 300 nm); the helices can extend into the cytoplasm and probably contain messenger RNA. Along with DNA and RNA-containing structures, some cells contain purely protein inclusions in the form of spheres (for example, in the cells of growing eggs of many animals, in the cells of a number of protozoa), bundles of fibrils or crystalloids (for example, in the nuclei of many tissue cells of animals and plants, macronuclei of a number of ciliates). Phospholipids, lipoproteins, and enzymes (DNA polymerase, RNA polymerase, a complex of enzymes of the membrane of the egg, including adenosine triphosphatase, etc.) were also found in the egg.

Various special types of eggs are found in nature: giant growing eggs. eggs, especially fish and amphibians; I., containing giant polytene chromosomes (see Polythenia), for example, in the cells of the salivary glands of dipteran insects; compact, devoid of nucleoli I. spermatozoa and micronuclei s ciliates, completely filled with chromatin and not synthesizing RNA; Ya., in which chromosomes are constantly condensed, although nucleoli are formed (in some protozoa, in a number of insect cells); Ya., in which there was a two- or multiple increase in the number of sets of chromosomes (Polyploidy; figures 7, 9 ).

The main method of nuclear division is mitosis, characterized by the duplication and condensation of chromosomes, the destruction of nuclear cells (with the exception of many protozoa and fungi) and the correct separation of sister chromosomes into daughter cells. However, the cells of some specialized cells, especially polyploid ones, can divide by simple ligation (see Amitosis). Highly polyploid eggs can divide not only into 2, but also into many parts, and also bud ( figure 7 ). In this case, separation of entire chromosome sets can occur (so-called genome segregation).

Lit.: Guide to cytology, vol. 1, M. -L., 1965; Raikov I.B., Karyology of protozoa, Leningrad, 1967; Robertis E., Novinsky V., Saez F.,. Cell biology, trans. from English, M., 1973; Chentsov Yu. S., Polyakov V. Yu., Ultrastructure of the cell nucleus, M., 1974; The nucleus, ed. A. J. Dalton, F, Haguenau, N. Y. - L., 1968; The cell nucleus, ed. N. Busch, v. 1-3, N. Y. - L., 1974.

I. B. Raikov.

Scheme of the ultrastructure of the liver cell nucleus: zones of compact (cx) and loose (px) chromatin; nucleolus (yak) with intranucleolar chromatin (vx), perichromatin fibrils (arrows), perichromatin (pg) and interchromatin (ig) granules; ribonucleoprotein thread coiled into a ball (k); core shell (yao) with pores (n).

II Core (math.)

function TO(X,at), specifying the integral transformation

which translates the function f(y) into the function φ ( X). The theory of such transformations is related to the theory of linear integral equations (See Integral equations).

III Core (military)

a spherical solid impact projectile in smoothbore artillery. From the middle of the 14th century. They were made of stone, from the 15th century. iron, then cast iron (for large-caliber guns) and lead (for small-caliber guns). From the 16th century incendiary “red-hot” weapons were used. In the 17th century. Hollow explosive shells (grenades) filled with gunpowder became widespread. In the 2nd half of the 19th century. Due to the replacement of smooth-bore guns with rifled ones, they fell out of use.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

Synonyms:

Antonyms:

See what “Kernel” is in other dictionaries:

The atomic nucleus is the positively charged massive central part of an atom, consisting of protons and neutrons (nucleons). daughter nucleus a nucleus formed as a result of the disintegration of the mother nucleus. mother nucleus atomic nucleus experiencing... ... Nuclear energy terms

Noun, s., used. compare often Morphology: (no) what? kernels, what? core, (I see) what? core, what? core, what? about the core; pl. What? kernels, (no) what? cores, what? cores, (I see) what? kernels, what? kernels, what are you talking about? about nuclei 1. The core is the internal,... ... Dmitriev's Explanatory Dictionary

KERNEL, cores, many. cores, cores, cores, cf. 1. Interior fruit in a hard shell. Walnut kernel. 2. only units. Internal, middle, central part of something (special). Wood core. Core of the earth (geol.). Ovule nucleus (bot.). Comet nucleus... ... Ushakov's Explanatory Dictionary

Wed. nucleolus, core, core, very middle, inside a thing, its interior or middle depth; concentrated essence, essence, basis; solid, strong, or most importantly, important, essential; | round body, ball. From these two meanings other meanings are derived: Son... Dahl's Explanatory Dictionary

- (nucleus), an obligatory part of the cell in plural. unicellular and all multicellular organisms. Based on the presence or absence of formed self in the cells, all organisms are divided into eukaryotes and prokaryotes, respectively. Basic the differences lie in the degree... ... Biological encyclopedic dictionary

core- NUCLEUS1, a, mn nuclei, nuclei, nuclei. The inner part of the fruit, enclosed in a hard shell. Core walnut externally very similar to the brain of a mammal. CORE2, a, pl nuclei, nuclei, cf The internal central part of an object (consisting of ... ... Explanatory dictionary of Russian nouns

Cm … Synonym dictionary

A; pl. cores, cores, cores; Wed 1. The inner part of a fruit (usually a nut), enclosed in a hard shell. * And the nuts are not simple: All the shells are golden, The kernels are pure emerald (Pushkin). Don’t crack the nut, don’t eat the kernel (Sequel). 2. Internal,... ... encyclopedic Dictionary

Good day, dear visitor. Today we’ll talk about what processor cores are and what function they perform. We want to say right away that we are not going to go into the jungle, which not every tech geek can handle. Everything will be accessible, understandable and relaxed, so grab your sandwiches.

I would like to start with the fact that the processor is the central module in the computer, which is responsible for all mathematical calculations, logical operations and data processing. In fact, all its power is concentrated, oddly enough, in the core. Their quantity determines the speed, intensity and quality of processing of the received information. Therefore, let’s take a closer look at the component.

Main characteristics of CPU cores

The core is a physical element of the processor (not to be confused with logical cores -), which affects the performance of the system as a whole.

Each product is built on a specific architecture, which indicates a certain set of properties and capabilities inherent in the line of manufactured chips.

Main distinctive feature– , i.e. the size of the transistors used in the production of the chip. The indicator is measured in nanometers. It is transistors that are the basis for the CPU: the more of them are placed on the silicon substrate, the more powerful a particular instance of the chip is.

Let's take for example 2 device models from Intel - Core i7 2600k and Core i7 7700k. Both have 4 cores in the processor, but the process technology is significantly different: 32 nm versus 14 nm, respectively, with the same die area. What does this affect? The latter shows the following indicators:

base frequency – higher;
heat release – lower;
the set of executable instructions is wider;
maximum memory bandwidth – greater;
support more functions.

In other words, reduction in technical process = increase in productivity. This is an axiom.

Kernel functions

The central processor core performs 2 main types of tasks:

intrasystem;
custom.

The second includes application support functions through the use of a software environment. Actually, application programming is precisely designed to load the CPU with the tasks that it will perform. The developer's goal is to set the priorities for performing a particular procedure.

Modern operating systems allow you to intelligently use all processor cores, which gives maximum system productivity. From this it is worth noting a banal but logical fact: the more physical cores on the processor, the faster and more stable your PC will work.

How to enable all cores to work

Some users, in pursuit of maximum performance, want to use all the processing power of the CPU. There are several ways to do this, which can be used individually or combined several points:

unlocking hidden and unused cores (not suitable for all processors - you need to study the instructions on the Internet in detail and check your model);
activation of the mode to increase the frequency for a short period;
manual overclocking of the processor.

The simplest method to start all active kernels at once is as follows:

open the Start menu with the corresponding button;
enter the command “msconfig.exe” in the search bar (only without quotes);
open the “additional parameters” item and set the required values in the “number of processors” column, after activating the checkbox opposite the line.

How to enable all cores in Windows 10?

Now, when Windows starts, all computing physical cores will work at once (not to be confused with threads).

For owners of older AMD processors

The following information will be useful to owners of older AMD processors. If you are still using the following chips, you will be pleasantly surprised:
The technology for unlocking additional cores is called ACC (Advanced Clock Calibration). It is supported on the following chipsets:
The utility that allows you to open additional kernels is called differently for each manufacturer:
In this simple way you can turn a 2-core system into a 4-core one. Most of you didn't even know about this, right? Let's hope I helped you achieve productivity improvements for free.

In this article, I tried to explain to you in as much detail as possible what a core is, what it consists of, what functions it performs and what potential it has.

In the following educational programs, many more interesting things await you, and therefore not material. Bye bye.

These days it's minimal acceptable norm more or less serious configuration computer technology It is considered to have a dual-core processor. Moreover, this parameter is relevant even for mobile computer devices, tablet PCs and reputable smartphone communicators. Therefore, we will figure out what kind of kernels these are and why it is important for any user to know about them.

The essence in simple words

The first dual-core chip, intended specifically for mass consumption, appeared in May 2005. The product was called Pentium D (formally belonged to the Pentium 4 series). Previously, similar structural solutions were used on servers and for specific purposes; they were not inserted into personal computers.

In general, the processor itself (microprocessor, CPU, Central Processing Unit, central processing unit, CPU) is a crystal onto which billions of microscopic transistors, resistors and conductors are applied using nanotechnology. Then gold contacts are sprayed, the “pebble” is mounted in the microcircuit body, and then all this is integrated into the chipset.

Now imagine that two such crystals are installed inside the microcircuit. On the same substrate, interconnected and acting as a single device. This is the two-core subject of discussion.

Of course, two “pebbles” are not the limit. At the time of writing, a PC equipped with a chip with four cores is considered powerful, not counting the computing resources of the video card. Well, thanks to the efforts of AMD, servers already use as many as sixteen.

Terminology nuances

Each die typically has its own L1 cache. However, if they have a common second-level one, then it is still one microprocessor, and not two (or more) independent ones.

A core can be called a full-fledged separate processor only if it has its own cache of both levels. But this is only necessary for use on very powerful servers and all kinds of supercomputers (favorite toys of scientists).

However, the “Task Manager” in Windows OS or the “System Monitor” in GNU/Linux can show kernels as CPUs. I mean, CPU 1 (CPU 1), CPU 2 (CPU 2) and so on. Don’t let this mislead you, because the program’s duty is not to understand the engineering and architectural nuances, but only to interactively display the loading of each of the crystals.

This means that we smoothly move on to this very loading and, in general, to questions of the expediency of the phenomenon as such.

Why is this necessary?

A number of cores different from one is intended primarily for parallelizing the tasks being performed.

Let's say you turn on your laptop and are reading sites on the World Wide Web. Scripts with which modern web pages are simply obscenely overloaded (except for mobile versions) will be processed by only one core. One hundred percent of the load will fall on it if something bad drives the browser crazy.

The second crystal will continue to operate in normal mode and will allow you to cope with the situation - at a minimum, open “System Monitor” (or a terminal emulator) and forcefully terminate the crazy program.

By the way, it is in the “System Monitor” that you can see with your own eyes which software has suddenly gone off the rails and which of the “pebbles” is causing the cooler to howl desperately.

Some programs are initially optimized for multi-core processor architecture and immediately send different data streams to different crystals. Well, ordinary applications are processed according to the “one thread - one core” principle.

That is, the performance gain will be noticeable if more than one thread is running at the same time. Well, since almost all operating systems are multitasking, the positive effect of parallelization will appear almost constantly.

How to live with it

Regarding consumer computing technology, single-core chips today are mainly ARM processors in simple phones and miniature media players. Outstanding performance from such devices is not required. The maximum is to launch the Opera Mini browser, an ICQ client, a simple game, and other unpretentious applications in Java.

Everything else, starting even with the cheapest tablets, must have at least two crystals in the chip, as stated in the preamble. Buy these things. Based at least on the considerations that almost all user software is rapidly getting fatter, consuming more and more system resources, so a power reserve will not hurt at all.

Previous publications:

Cell biology of living organisms studies prokaryotes that do not have a nucleus (nucleus, core). Which organisms are characterized by the presence of a nucleus? The nucleus is the central organelle.

In contact with

Important! The main function of the cell nucleus is the storage and transmission of hereditary information.

Structure

What is the core? What parts does the nucleus consist of? Components listed below are part of core:

Nuclear envelope;
Nucleoplasm;
Karyomatrix;
Chromatin;
Nucleols.

Nuclear envelope

Karyolemma consists of two layers- external and internal, separated by a perinuclear cavity. The outer membrane communicates with rough endoplasmic tubules. The fibrillar proteins of the core of the nuclear substance are attached to the inner shell. Between the membranes there is a perinuclear cavity formed by the mutual repulsion of ionized organic molecules with similar charges.

The karyolemma is penetrated by a system of openings - pores formed by protein molecules. Through them, ribosomes, the structures in which protein synthesis occurs, as well as messenger RNAs penetrate the cytoplasmic reticulum.

Intermembrane pores are tubules filled with. Their walls are formed by specific proteins - nucleoporins. The diameter of the hole allows the cytoplasm and the contents of the nucleus to exchange small molecules. Nucleic acids, as well as high molecular weight proteins, are not able to independently flow from one part of the cell to another. For this purpose, there are special transport proteins, the activation of which occurs with energy costs.

High molecular weight compounds move through pores with the help of karyopherins. Those that transport substances from the cytoplasm to the nucleus are called importins. Movement in the opposite direction is carried out by exportins. In what part of the nucleus is the RNA molecule located? She travels throughout the cell.

Important! High-molecular substances cannot independently penetrate through the pores from the core to and from the core.

Nucleoplasm

Represented by karyoplasm- a gel-like mass located inside a two-layer shell. Unlike the cytoplasm, where pH >7, the environment inside the nucleus is acidic. The main substances that make up the nucleoplasm are nucleotides, proteins, cations, RNA, H2O.

Karyomatrix

What components make up the core? It is formed by fibrillar proteins of a three-dimensional structure - lamins. Plays the role of a skeleton, preventing deformation of the organoid under mechanical stress.

Chromatin

This main substance, represented by a set of chromosomes, some of which are in an activated state. The rest are packed in compacted blocks. Their opening occurs during division. What part of the nucleus contains the molecule we know as DNA? consist of genes, which are parts of a DNA molecule. They contain information that transmits hereditary characteristics to new generations of cells. Therefore, this part of the nucleus contains a DNA molecule.

In biology they distinguish the following types of chromatin:

Euchromatin. Appears as filamentous, despiralized, non-staining formations. It exists in the resting nucleus during the interphase between cycles of cell division.
Heterochromatin. Non-activated spiralized, easily stained regions of chromosomes.

Nucleols

The nucleolus is the most compacted structure that makes up the nucleus. It has predominantly round shapes, however, there are segmented ones, like leukocytes. The nucleus of the cells of some organisms does not have nucleoli. In other cores there may be several of them. The substance of the nucleoli is represented by granules, which are subunits of ribosomes, as well as fibrils, which are RNA molecules.

Nucleolus: structure and functions

Nucleols are represented by the following structural types:

Reticular. Typical for most cells. It is characterized by a high concentration of compacted fibrils and granules.
Compact. Characterized by a multiplicity of fibrillar accumulations. Found in dividing cells.
Annular. Characteristic of lymphocytes and connective tissue cells.
Residual. Prevails in cells where the division process does not occur.
Separated. All components of the nucleolus are separated, plastic actions are impossible.

Functions

What function does the kernel perform? Nucleus is characterized by the following responsibilities:

Transfer of hereditary characteristics;
Reproduction;
Programmed death.

Storage of genetic information

Genetic codes are stored in chromosomes. They differ in shape and size. Individuals different types have an unequal number of chromosomes. The complex of characteristics characteristic of the repositories of hereditary information of a given species is called a karyotype.

Important! A karyotype is a set of characteristics characteristic of the chromosomal composition of organisms of a given species.

There are haploid, diploid, and polyploid sets of chromosomes.

The cells of the human body contain 23 types of chromosomes. The egg and sperm contain a haploid, that is, a single set of them. During fertilization, the stores of both cells combine, forming a double - diploid set. Cells cultivated plants triploid or tetraploid karyotype is inherent.

Storage of genetic information

Transmission of hereditary characteristics

What vital processes occur in the nucleus? Gene coding is transmitted during the process of reading information, which results in the formation of messenger (messenger) RNA. Exportins excrete ribonucleic acid through nuclear pores into the cytoplasm. Ribosomes use genetic codes to synthesize proteins needed by the body.

Important! Protein synthesis occurs in cytoplasmic ribosomes based on encoded genetic information delivered by messenger RNA.

Reproduction

Prokaryotes reproduce simply. Bacteria have a single DNA molecule. In the process of division she copies herself attaching to the cell membrane. The membrane grows between the two junctions and two new organisms are formed.

In eukaryotes there are amitosis, mitosis and meiosis:

Amitosis. Nuclear division occurs without cell fragmentation. Binuclear cellae are formed. During the next division, polynuclear formations may appear. What organisms are characterized by such reproduction? Aging, non-viable, and tumor cells are susceptible to it. In some situations, amitotic division to form normal cells occurs in the cornea, liver, cartilaginous textures, and also in the tissues of some plants.
Mitosis. In this case, nuclear fission begins with its destruction. A cleavage spindle is formed, with the help of which paired chromosomes are separated to different ends of the cell. Replication of the carriers of heredity occurs, after which two nuclei are formed. After this, the spindle is dismantled and a nuclear membrane is formed, which divides one cell into two.
Meiosis. A complex process in which nuclear division occurs without duplication of diverged chromosomes. Characteristic for the formation of germ cells - gametes that have a haploid set of carriers of heredity.

Programmed Doom

Genetic information provides for the life span of the cell, and after the allotted time, it starts the process of apoptosis (Greek - leaf fall). Chromatin condenses and the nuclear membrane is destroyed. The cella disintegrates into fragments limited to the plasma membrane. Apoptotic bodies, bypassing the stage of inflammation, are absorbed by macrophages or neighboring cells.

For clarity, the structure of the core and the functions performed by its parts are presented in the table

Core element	Structural features	Functions performed
Shell	Double layer membrane	Distinguishing the contents of the nucleus and cytoplasm
Pores	Holes in the shell	Export - import RNA
Nucleoplasm	Gel-like consistency	Medium for biochemical transformations
Karyomatrix	Fibrillar proteins	Support structure, protect against deformation
Chromatin	Euchromatin, heterochromatin	Storage of genetic information
Nucleola	Fibrils and granules	Ribosome production

Appearance

The shape is determined by the configuration of the membrane. The following types of nuclei are noted:

Round. The most common one. For example, most of the lymphocyte is occupied by the nucleus.
Elongated. The horseshoe-shaped nucleus is found in immature neutrophils.
Segmented. Partitions form in the shell. Segments attached to each other are formed, such as in a mature neutrophil.
Branched. Found in the nuclei of arthropod cells.

Number of Cores

Depending on the functions they perform, cellas may have one or more cores or not have them at all. The following types of cells are distinguished:

Non-nuclear. The formed components of the blood of higher animals are erythrocytes, platelets are carriers of important substances. To make room for hemoglobin or fibrinogen, the bone marrow produces these elements nuclear-free. They are not able to divide and die off after the programmed time has passed.
Single core. This is the case with most cells of living organisms.
Binuclear. Liver hepatocytes perform a dual function - detoxification and production. Heme is synthesized, which is necessary for the production of hemoglobin. For these purposes, two cores are required.
Multi-core. Muscle myocytes perform a colossal amount of work; additional nuclei are required to perform it. For the same reason, the cells of angiosperms are polynuclear.

Chromosomal pathologies

Many diseases are the result of disorders associated with abnormalities in chromosomal composition. The most well-known symptom complexes are:

Down. Caused by the presence of an extra twenty-first chromosome (trisomy).
Edwards. An extra eighteenth chromosome is present.
Patau. Trisomy 13.
Turner. The X chromosome is missing.
Klinefelter. Characterized by extra X or Y chromosomes.

Illnesses caused by dysfunction components nuclei are not always associated with chromosomal abnormalities. Mutations that affect individual nuclear proteins cause the following diseases:

Laminopathy. Manifested by premature aging.
Autoimmune diseases. Lupus erythematosus is a diffuse lesion of connective tissue textures, multiple sclerosis is the destruction of the myelin sheaths of nerves.

Important! Chromosomal abnormalities lead to severe diseases.

Core structure

Biology in pictures: Structure and functions of the nucleus

Conclusion

The cell nucleus has a complex structure and performs vital functions. It is a repository and transmitter of hereditary information, controls the synthesis of proteins and the processes of cell division. Chromosomal abnormalities are the causes of severe diseases.

The cell nucleus is the central organelle, one of the most important. Its presence in the cell is a sign of high organization of the organism. A cell that has a formed nucleus is called eukaryotic. Prokaryotes are organisms consisting of a cell that does not have a formed nucleus. If we consider all its components in detail, we can understand what function the cell nucleus performs.

Core structure

Nuclear envelope.
Chromatin.
Nucleoli.
Nuclear matrix and nuclear juice.

The structure and function of the cell nucleus depends on the type of cell and its purpose.

Nuclear envelope

The nuclear envelope has two membranes - outer and inner. They are separated from each other by the perinuclear space. The shell has pores. Nuclear pores are necessary so that various large particles and molecules can move from the cytoplasm to the nucleus and back.

Nuclear pores are formed by the fusion of the inner and outer membranes. Pores are round openings with complexes that include:

A thin diaphragm that closes the hole. It is penetrated by cylindrical channels.
Protein granules. They are located on both sides of the diaphragm.
Central protein granule. It is associated with peripheral granules by fibrils.

The number of pores in the nuclear membrane depends on how intensively synthetic processes take place in the cell.

The nuclear envelope consists of outer and inner membranes. The outer one passes into the rough ER (endoplasmic reticulum).

Chromatin

Chromatin is the most important substance included in the cell nucleus. Its functions are the storage of genetic information. It is represented by euchromatin and heterochromatin. All chromatin is a collection of chromosomes.

Euchromatin is parts of chromosomes that actively participate in transcription. Such chromosomes are in a diffuse state.

Inactive sections and entire chromosomes are condensed clumps. This is heterochromatin. When the state of the cell changes, heterochromatin can transform into euchromatin, and vice versa. The more heterochromatin in the nucleus, the lower the rate of ribonucleic acid (RNA) synthesis and the lower the functional activity of the nucleus.

Chromosomes

Chromosomes are special formations that appear in the nucleus only during division. A chromosome consists of two arms and a centromere. According to their form they are divided into:

Rod-shaped. Such chromosomes have one large arm and the other small.
Equal-armed. They have relatively identical shoulders.
Mixed shoulders. The arms of the chromosome are visually different from each other.
With secondary constrictions. Such a chromosome has a non-centromeric constriction that separates the satellite element from the main part.

In each species, the number of chromosomes is always the same, but it is worth noting that the level of organization of the organism does not depend on their number. Thus, a person has 46 chromosomes, a chicken has 78, a hedgehog has 96, and a birch has 84. The fern Ophioglossum reticulatum has the largest number of chromosomes. It has 1260 chromosomes per cell. The male ant of the species Myrmecia pilosula has the smallest number of chromosomes. He only has 1 chromosome.

It was by studying chromosomes that scientists understood the functions of the cell nucleus.

Chromosomes contain genes.

Gene

Genes are sections of deoxyribonucleic acid (DNA) molecules that encode certain compounds protein molecules. As a result, the body exhibits one or another symptom. The gene is inherited. Thus, the nucleus in a cell performs the function of transmitting genetic material to the next generations of cells.

Nucleoli

The nucleolus is the densest part that enters the cell nucleus. The functions it performs are very important for the entire cell. Usually has a round shape. The number of nucleoli varies in different cells - there may be two, three, or none at all. Thus, there is no nucleolus in the cells of crushed eggs.

Structure of the nucleolus:

Granular component. These are granules that are located on the periphery of the nucleolus. Their size varies from 15 nm to 20 nm. In some cells, HA may be evenly distributed throughout the nucleolus.
Fibrillar component (FC). These are thin fibrils, ranging in size from 3 nm to 5 nm. Fk is the diffuse part of the nucleolus.

Fibrillar centers (FCs) are areas of fibrils that have a low density, which, in turn, are surrounded by fibrils with a high density. Chemical composition and the structure of the PCs is almost the same as that of the nucleolar organizers of mitotic chromosomes. They consist of fibrils up to 10 nm thick, which contain RNA polymerase I. This is confirmed by the fact that the fibrils are stained with silver salts.

Structural types of nucleoli

Nucleolonemal or reticular type. Characterized by a large number of granules and dense fibrillar material. This type of nucleolar structure is characteristic of most cells. It can be observed both in animal cells and in plant cells.
Compact type. It is characterized by a low severity of nucleonoma and a large number of fibrillar centers. It is found in plant and animal cells, in which the process of protein and RNA synthesis actively occurs. This type of nucleoli is characteristic of cells that are actively reproducing (tissue culture cells, plant meristem cells, etc.).
Ring type. In a light microscope, this type is visible as a ring with a light center - a fibrillar center. The size of such nucleoli is on average 1 micron. This type is characteristic only of animal cells (endotheliocytes, lymphocytes, etc.). In cells with this type of nucleoli there are quite low level transcriptions.
Residual type. In cells of this type of nucleoli, RNA synthesis does not occur. Under certain conditions, this type can become reticular or compact, that is, activated. Such nucleoli are characteristic of cells of the spinous layer of the skin epithelium, normoblast, etc.
Segregated type. In cells with this type of nucleolus, rRNA (ribosomal ribonucleic acid) synthesis does not occur. This occurs if the cell is treated with any antibiotic or chemical. The word "segregation" in in this case means “separation” or “separation”, since all the components of the nucleoli are separated, which leads to its reduction.

Almost 60% of the dry weight of the nucleoli is protein. Their number is very large and can reach several hundred.

The main function of the nucleoli is the synthesis of rRNA. Ribosome embryos enter the karyoplasm, then leak through the pores of the nucleus into the cytoplasm and onto the ER.

Nuclear matrix and nuclear sap

The nuclear matrix occupies almost the entire cell nucleus. Its functions are specific. It dissolves and distributes everything evenly nucleic acids in a state of interphase.

The nuclear matrix, or karyoplasm, is a solution that contains carbohydrates, salts, proteins and other inorganic and organic substances. It contains nucleic acids: DNA, tRNA, rRNA, mRNA.

During cell division, the nuclear membrane dissolves, chromosomes are formed, and the karyoplasm mixes with the cytoplasm.

The main functions of the nucleus in a cell

Informative function. It is in the nucleus that all the information about the heredity of the organism is located.
Inheritance function. Thanks to genes located on chromosomes, an organism can pass on its characteristics from generation to generation.
Merge function. All cell organelles are united into one whole in the nucleus.
Regulation function. All biochemical reactions in the cell and physiological processes are regulated and coordinated by the nucleus.

One of the most important organelles is the cell nucleus. Its functions are important for the normal functioning of the entire organism.

Sections