Organisms whose cells do not have membrane-bound nuclei. Structure and functions of the nucleus Organisms that have a separate nucleus are called

What organisms are we talking about? These organisms consist of a single cell; The cell has a wall; Cells do not have nuclei; Hereditary information is concentrated in a single chromosome; Metabolism occurs through the process of CHEMOSYNTHESIS or PHOTOSYNTHESIS; Appeared 3.8 - 3.1 billion years ago.

PROKARYOTES (BACTERIA) 1. The cell contains: Capsule Cell wall Plasma membrane Fixed cytoplasm Ribosomes Nucleoid 2. The cell does not have: Nucleus Many organelles EUKARYOTES (plants, fungi, animals) 1. The cell contains: NUCLEUS Cell wall (P and G) Plasma membrane Mobile cytoplasm Organelles - endoplasmic reticulum - mitochondria - vacuoles - plastids - ribosomes, etc.

Basic terms and concepts EUKARYOTES are organisms whose cells have a formed nucleus. PROKARYOTES are organisms whose cells do NOT have a formed nucleus. BACTERIA is a very small, single-celled, non-nuclear organism. CAPSULE – an additional layer of mucus on the surface of a bacterial cell.

Control: 1. Bacteria – unicellular and multicellular plants. 2. Some bacterial cells have a nucleus. 3. Bacteria, unlike plants, do not have a cellular structure. 4. Vibrios are considered rod-shaped bacteria. 5. A bacterial cell contains cytoplasm and ribosomes.

7. Aerobe 8. Anaerobe 9. Fermentation - an organism that requires oxygen for its life. -an organism that does not require oxygen to function. -the process of extracting energy from nutrients in an oxygen-free environment (energetically unprofitable).

The importance of bacteria in NATURE: They take an active part in the cycle of substances, changing organic and inorganic compounds; Enrichment of atmospheric oxygen (cyanobacteria); Food object for other organisms; Soil formation (formation of humus and humus) – soil bacteria; Increasing soil fertility (nitrogen-fixing bacteria); Causes diseases of plants and animals

The importance of bacteria in human life: ECOLOGICAL 1(+). Wastewater treatment at wastewater treatment plants, waste recycling; 2(+). Cleaning the waters of the World Ocean from oil spills (during oil spills); 3(+). Formation of mineral deposits (gas, oil, sulfur, iron). 4(-). Food spoilage. Control measures: a) boiling; b) drying; c) sterilization; d) pasteurization; d) freezing.

What are the measures to prevent bacterial diseases? 1. Ventilation and wet cleaning of premises; 2. Observe the rules of personal hygiene; 3. Do not eat unwashed or expired foods; 4. Prepare food properly; 5. Avoid promiscuity; 6. Boil tap water, as well as from unknown sources; 7. Conduct timely vaccinations; 8. Destroy and disinfect sick and dead animals. Bacteria is the object of study; The activity of bacteria is used in the production of: 1. Medicines - antibiotics; 2. Hormones – insulin; 3. Food products: -fermented milk products, cheeses; -winemaking, brewing; - pickling vegetables; -preparing vinegar; -silage.

Control: 1. Diphtheria, tetanus, tuberculosis, cholera, typhoid fever are bacterial diseases. 2. E. coli lives in the human digestive system. 3. Bacteria actively participate in the cycle of substances in nature. 4. Nodule bacteria, being in symbiosis with leguminous plants, are able to absorb phosphorus. 5. Flu and sore throat are diseases caused by bacteria. 6. What bacteria play the role of orderlies in nature? 7. What bacteria cause the fermentation process?

2731. Indicate one of the provisions of the cell theory
A) The unit of structure, life activity and development of organisms is the cell
B) The germ cell contains one allele of each gene
B) A multicellular embryo is formed from the zygote
D) In the nuclei of eukaryotic cells, genes are located linearly on chromosomes

Abstract

2732. How many autosomes are contained in a human sperm?
A) 22
B) 2
B) 23
D) 4

Abstract

2733. Organisms whose cells have a separate nucleus are
A) eukaryotes
B) bacteria
B) prokaryotes
D) viruses

Abstract

2734. Parthenogenesis is a type of sexual reproduction in which a new organism develops from
A) diploid zygote
B) the first blastomeres
B) haploid spore
D) unfertilized egg

Abstract

2735. The skin of tomato fruits can be smooth and pubescent (a). Select
genotypes of parent plants that have dominant phenotypes.
A) Aa, aa
B) Aa, Aa
B) A, a
D) AA, aa

Abstract

2736. Inheritance of the hemophilia gene, located on the X chromosome in humans, is an example
A) manifestations of the result of crossing over
B) sex-linked inheritance
B) independent inheritance of traits
D) intermediate inheritance of traits

2737. The appearance of different alleles of one gene occurs as a result
A) indirect cell division
B) modification variability
B) mutation process
D) combinative variability

2738. Why are bacteria classified as an independent kingdom of the organic world?
A) under unfavorable conditions they reproduce by mitosis
B) absence of a nucleus in the cell
B) reproduce by spores
D) mostly heterotrophic organisms

Abstract

2739. The growth of the stem of a woody plant in thickness occurs due to cell division and growth
A) cambium
B) wood
B) traffic jams
D) bast

2740. Angiosperms are more highly organized plants than gymnosperms, since they form
A) zygote during the fusion of gametes
B) seeds from ovules
B) fruits with seeds
D) embryo protected by the seed coat

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Special purpose organelles are found in many plant and animal cells. These include organelles of movement (myofibrils, cilia, flagella, stinging capsules, etc.), supporting structures (tonofibrils), organelles that perceive external stimuli (for example, photoreceptors, stator receptors and phonoreceptors), neurofibrils, as well as cell surface structures associated with absorption and digestion of food (microvilli, cuticle, etc.)

Cilia and flagella - these are organelles protruding from the cell, having a diameter of about 0.25 microns and containing in the middle a bundle of parallel microtubules. The main function of these organelles is to move the cells themselves or to move the surrounding fluid and particles along the cells. Cilia and flagella are present on the surface of many types of cells and are found in most animals and some plants. In humans, bronchial epithelial cells have many cilia (up to 10#9 per 1 cm2). They cause a layer of mucus with dust particles and the remains of dead cells to constantly move upward. With the help of the cilia of the oviduct cells, the eggs move along it. Flagella differ from cilia only in length. Thus, mammalian sperm have one flagellum up to 100 microns long.

Organisms whose cells do not have membrane-bound nuclei.

Typically, cilia are more than 10 times shorter than flagella. Thousands of cilia of one cell move in a coordinated manner, forming traveling waves on the surface of the plasma membrane. Each cilium works like a whip: a forward blow, in which the cilium fully straightens and transmits maximum force to the surrounding fluid, pushing it, and then, bending to reduce the resistance of the medium, it returns to the original position). Microtubules—hollow protein cylinders with an outer diameter of 25 nm—stretch along the entire length of the cilium or flagellum. Microtubules, like microfilaments, are polar; they elongate at one end due to the polymerization of the globular protein. In cilia and flagella they are arranged according to the 9+2 system; nine double microtubules (doublets) form the wall of a cylinder, in the center of which there are two single microtubules. The doublets are able to slide relative to each other, which causes the cilium or flagellum to bend.

Microtubules

Microtubules - protein intracellular structures that make up the cytoskeleton. Microtubules are hollow cylinders with a diameter of 25 nm. Their length can range from several micrometers to probably several millimeters in the axons of nerve cells. Their wall is formed by tubulin dimers. Microtubules, like actin microfilaments, are polar: microtubule self-assembly occurs at one end, and disassembly occurs at the other. In cells, microtubules play the role of structural components and are involved in many cellular processes, including mitosis, cytokinesis and vesicular transport. Contents [show]

Structure of Microtubules are structures in which 13 tubulin α-/β-heterodimers are arranged around the circumference of a hollow cylinder. The outer diameter of the cylinder is about 25 nm, the inner diameter is about 15. One of the ends of the microtubule, called the plus end, constantly attaches free tubulin to itself. From the opposite end - the minus end - tubulin units are split off.

Function Microtubules in the cell are used as “rails” for transporting particles. Membrane vesicles and mitochondria can move along their surface. Transportation along microtubules is carried out by proteins called motor proteins. These are high-molecular compounds consisting of two heavy (weighing about 300 kDa) and several light chains. Heavy chains have head and tail domains. The two head domains bind to microtubules and act as motors themselves, while the tail domains bind to organelles and other intracellular structures to be transported.

In addition to their transport function, microtubules form the central structure of cilia and flagella - the axoneme. A typical axoneme contains 9 pairs of united microtubules at the periphery and two complete microtubules in the center. Microtubules also consist of centrioles and the spindle, which ensures the divergence of chromosomes to the poles of the cell during mitosis and meiosis. Microtubules are involved in maintaining cell shape and the location of organelles (in particular, the Golgi apparatus) in the cytoplasm of cells.

ORGANOIDS FOR SPECIAL PURPOSE

Microtubules – long thin hollow cylinders with a diameter of 25 nm. microtubule walls are made of proteins	1. supporting function - forming an internal frame that helps cells maintain their shape 2. motor - part of cilia and flagella
Mvyrosikroniti – thin structures consisting of thousands of protein molecules connected to each other	They form a musculoskeletal system called the cytoskeleton. promotes cytoplasmic flow in cells
Eyelashes – numerous cytoplasmic projections on the membrane surface are formed by membrane-covered microtubules	Ensure the movement of some single-celled organisms and the flow of fluid in organisms and the removal of dust particles
Flagella– a surface structure present in many prokaryotic and eukaryotic cells and serving for their movement in a liquid environment or on the surface of solid media. The flagella of prokaryotes and eukaryotes differ sharply: the bacterial flagellum has a thickness of 10-20 nm and a length of 3-15 µm, it is passively rotated by a motor located in the membrane; flagella of eukaryotes are up to 200 nm thick and up to 200 microns long; they can independently bend along their entire length. Eukaryotes often also have cilia, identical in structure to the flagellum, but shorter (up to 10 µm).	Serve for the movement of single-celled organisms, sperm and zoospores

Question 17.

Inclusions– optional components of the cell that appear and disappear depending on the metabolic state of the cell.

This is an accumulation of substances in a cell.

Classification:

Trophic (neutral lipids, polysaccharides, proteins)

Secretory (vacuoles that remove substances from the cell)

Excretory (metabolic products)

Pigment - exogenous (carotene, dust, dyes)

- endogenous (hemoglobin, melanin)

Eukaryotes are organisms whose cells have a nucleus surrounded by a membrane.

Features of the structure:

The shape of the cells is varied, the sizes range from 5 to 100 microns.
Cells have similar chemical composition and metabolism.
Cells are divided by a system of membranes into compartments.
The genetic material is concentrated mainly in chromosomes, which have a complex structure and are formed by DNA strands and histone protein molecules.
The cytoplasm contains membrane organelles and centrioles.
Cell division is mitotic.

Core– an obligatory structural component of every eukaryotic cell containing genetic material. In animal cells, hereditary information is stored in nucleus and mitochondria. In plant cells - in the core, mitochondria and plastids. The core consists of:

1. Nuclear envelope;

2. Karyoplasm;

3. Chromatin;

4. Nucleolus.

The shape of the nucleus depends on the shape of the cell itself and the functions it performs.

The size of the nucleus also mainly depends on the size of the cell.

Nuclear-cytoplasmic index – ratio of the volumes of the nucleus and cytoplasm. A change in this ratio is one of the causes of cell division or metabolic disorders.

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The internal “skeleton” of the nucleus is of great importance for ensuring the orderly flow of basic processes transcription, replication, processing. The outside of the core is also covered microfilaments, which are elements cell cytoskeleton. The outer nuclear membrane has on its surface ribosomes and associated with membranes endoplasmic reticulum. The nuclear envelope has selective permeability. The flow of substances is regulated by the specific features of membrane proteins and nuclear pores (from 1000 to 10000).

Main functions of the nuclear membrane.

1. Formation of a cell compartment where the genetic material is concentrated and conditions are created for its preservation and doubling.

2. Separation of the contents of the nucleus from the cytoplasm.

3. Maintaining the shape and volume of the core.

4. Regulation of substance flows (various types of RNA and ribosomal subunits enter the cytoplasm from the nucleus through pores, and the necessary proteins, water, and ions are transferred to the middle of the nucleus).

Karyoplasm – a homogeneous structureless mass that fills the space between chromatin and nucleoli. It contains water (75-80%), proteins, nucleotides, amino acids, ATP, various types of RNA, ribosomal subparticles, intermediate metabolic products and interconnects the structures of the nucleus and cytoplasm.

Chromatin

The genetic material in the interphase nucleus is in the form

intertwined chromatin threads. It is a complex of DNA and proteins (deoxyribonucleoprotein- DNP). During the process of mitosis, spiraling, chromatin forms clearly visible, intensely stained structures. – CHROMOSOMES.

Nucleoli(one or more) – granular, round, highly stained structures that do not have a membrane. Nucleoli are composed of proteins, RNA, lipids and enzymes. The DNA content is no more than 15% and is located mainly in its center.

Nucleoli are fragmented at the beginning of cell division and restored after its completion. In the nucleoli there are 3 plots:

1. Fibrillar;

2. Granular;

3. Lightly colored.

— Fibrillar region of the nucleolus consists of strands of RNA. This is the site of active synthesis of ribosomal RNA on rRNA genes along the DNA molecule of decondensed chromatin.

— Granular area consists of RNA particles similar to ribosomes in the cytoplasm. It is the site where RNA and ribosomal proteins combine to form mature small and large ribosomal subunits.

— Lightly colored area The nucleolus contains DNA (inactive) that is not transcribed.

The formation of nucleoli is associated with secondary constrictions of metaphase chromosomes (nucleolar organizers), in the region of which genes encoding r-RNA synthesis are localized. In human cells, these functions are performed by chromosomes No. 13, 14, 15, 21, 22, which have satellites or companions.

Main functions of nucleoli:

Synthesis of ribosomal RNA.
Formation of ribosomal subunits.

KERNEL FUNCTIONS:

1. Storage and transmission of hereditary information;

2. Regulation of all cell vital processes;

3. DNA repair;

4. Synthesis of all types of RNA;

5. Formation of ribosomes;

6. Implementation of hereditary information by regulating protein synthesis.

CHROMOSOMES.

Chromosomes – thread-like structures, clearly visible in a light microscope only during cell division, are formed from chromatin during the process of its condensation. Depending on the degree condensation chromatin is divided into:

1. Heterochromatin - strong spiralized and genetically inactive, revealed in the form of strongly colored dark areas of the nucleus.

2. Euchromatin – low condensed, genetically active, is detected in the form of light areas of the nucleus.

Chemical composition of chromosomes :

1. DNA – 40%

2. Basic or histone proteins – 40%

3. Non-histone (acidic or neutral) – 20%

4. Traces of RNA, lipids, polysaccharides, metal ions.

Only eukaryotic cells have a nucleus. However, some of them lose it in the process of differentiation (mature segments of sieve tubes, erythrocytes). Ciliates have two nuclei: macronucleus and micronucleus. There are multinucleated cells that arise from the union of several cells. However, in most cases, each cell has only one nucleus.

The cell nucleus is its largest organelle (except for the central vacuoles of plant cells). It is the very first cellular structure that was described by scientists. Cell nuclei are usually spherical or ovoid in shape.

The nucleus regulates all cell activity. It contains chromatids- thread-like complexes of DNA molecules with histone proteins (the peculiarity of which is that they contain a large amount of the amino acids lysine and arginine). The DNA of the nucleus stores information about almost all hereditary characteristics and properties of the cell and organism. During cell division, chromatids spiral, in this state they are visible under a light microscope and are called chromosomes.

Chromatids in a non-dividing cell (during interphase) are not completely despiraled. The tightly coiled parts of chromosomes are called heterochromatin. It is located closer to the core shell. Located towards the center of the core euchromatin- a more despiralized part of the chromosomes. RNA synthesis occurs on it, i.e., genetic information is read and genes are expressed.

DNA replication precedes nuclear division, which in turn precedes cell division. Thus, daughter nuclei receive ready-made DNA, and daughter cells receive ready-made nuclei.

The internal contents of the nucleus are separated from the cytoplasm nuclear envelope, consisting of two membranes (external and internal). Thus, the cell nucleus is a double-membrane organelle. The space between the membranes is called perinuclear.

The outer membrane in certain places passes into the endoplasmic reticulum (ER). If ribosomes are located on the EPS, then it is called rough. Ribosomes can also be located on the outer nuclear membrane.

In many places, the outer and inner membranes merge with each other, forming nuclear pores. Their number is variable (on average in the thousands) and depends on the activity of biosynthesis in the cell. Through pores, the nucleus and cytoplasm exchange various molecules and structures. Pores are not just holes; they are complexly designed for selective transport. Their structure is determined by various nucleoporin proteins.

Molecules of mRNA, tRNA, and ribosome subparticles emerge from the nucleus.

Various proteins, nucleotides, ions, etc. enter the nucleus through the pores.

Ribosomal subunits are assembled from rRNA and ribosomal proteins into nucleolus(there may be several). The central part of the nucleolus is formed by special sections of chromosomes ( nucleolar organizers), which are located next to each other. Nucleolar organizers contain large numbers of copies of rRNA-coding genes. Before cell division, the nucleolus disappears and is formed again during telophase.

The liquid (gel-like) contents of the cell nucleus are called nuclear juice (karyoplasm, nucleoplasm). Its viscosity is almost the same as that of hyaloplasm (the liquid content of the cytoplasm), but its acidity is higher (after all, DNA and RNA, of which there is a large amount in the nucleus, are acids). Proteins, various RNAs, and ribosomes float in the nuclear juice.

Bacteria are the smallest living organisms that inhabit our planet. What tiny bacteria don't have? Impressive size. It is impossible to notice them without a microscope, but their desire to live is truly amazing. The mere fact that bacteria, under favorable conditions, can remain in “lethargic sleep” for hundreds of years is respectable. What structural features help these babies live so long?

Prokaryotes are classified by scientists as a separate kingdom due to the fact that they have a specific cellular structure. These include:

bacteria;
blue-green algae;
rickettsia;
mycoplasma.

The absence of clearly defined nuclear walls is the main feature of representatives of the prokaryotic kingdom. Therefore, the center of genetic information is a single circular DNA molecule that is attached to the cell membrane.

What else is missing in the cellular structure of bacteria?

Nuclear envelope.
Mitochondria.
Plastid.
Ribosomal DNA.
Endoplasmic reticulum.
Golgi complex.

However, the absence of all these components does not prevent the ubiquitous microorganisms from being at the center of natural metabolism. They fix nitrogen, cause fermentation, and oxidize inorganic substances.

Reliable protection

Nature has taken care to provide protection to the babies: on the outside, the bacterial cell is surrounded by a dense membrane. The cell wall freely carries out metabolism. It lets nutrients in and waste products out.

The membrane determines the body shape of the bacterium:

spherical cocci;
curved vibrios;
rod-shaped bacilli;
spirilla.

To protect against drying out, a capsule is formed around the cell wall, which consists of a dense layer of mucus. The thickness of the capsule walls can exceed the diameter of the bacterial cell several times. The density of the walls varies depending on the environmental conditions to which the bacterium encounters.

The genetic pool is safe

Bacteria do not have a clearly defined nucleus that would contain DNA. But this does not mean that the genetic information in microorganisms without a nuclear membrane has a chaotic arrangement. The thread-like double helix of DNA is arranged in a neat coil in the center of the cell.

DNA molecules contain hereditary material, which is the center for launching the processes of reproduction of microorganisms. Bacteria are also equipped, like a wall, with a special protective system that helps repel attacks from viral DNA. The antiviral system works to damage foreign DNA, but does not damage its own DNA.

Thanks to the hereditary information recorded in DNA, bacteria multiply. Microorganisms reproduce by division. The speed at which these little ones are able to divide is impressive: every 20 minutes their number doubles! In favorable conditions, they are able to form entire colonies, but a lack of nutrients negatively affects the increase in the number of bacteria.

What is the cell filled with?

The bacterial cytoplasm is a storehouse of nutrients. This is a thick substance that is equipped with ribosomes. Under a microscope, accumulations of organic and mineral substances can be distinguished in the cytoplasm.

Depending on the functionality of the bacteria, the number of cellular ribosomes can reach tens of thousands. Ribosomes have a specific shape, the walls of which lack any symmetry and reach a diameter of 30 nm.

Ribosomes get their name from ribonucleic acids (RNA). During reproduction, it is the ribosomes that reproduce the genetic information recorded in DNA.

Ribosomes have become the center that directs the process of protein biosynthesis. Thanks to biosynthesis, inorganic substances are converted into biologically active ones. The process takes place in 4 stages:

Transcription. Ribonucleic acids are formed from double strands of DNA.
Transportation. The created RNAs transport amino acids to ribosomes as starting material for protein synthesis.
Broadcast. Ribosomes scan information and build polypeptide chains.
Protein formation.

Scientists have not yet studied in detail the structure and functionality of cellular ribosomes in bacteria. Their full structure is not yet known. Further work in the field of ribosome research will provide a complete picture of how the molecular machinery for protein synthesis works.

What is not included in a bacterial cell?

Unlike other living organisms, the structure of bacterial cells does not include many cellular structures. But their cytoplasm contains organelles that successfully perform the functions of mitochondria or the Golgi complex.

A huge number of mitochondria are found in eukaryotes. They make up approximately 25% of the total cellular volume. Mitochondria are responsible for the production, storage and distribution of energy. Mitochondria DNA are cyclic molecules and are collected in special clusters.

The walls of mitochondria consist of two membranes:

external, having smooth walls;
internal, from which numerous cristae extend deeper.

Prokaryotes are equipped with peculiar batteries, which, like mitochondria, supply them with energy. For example, such “mitochondria” behave very interestingly in yeast cells. For successful life, they need carbon dioxide. Therefore, under conditions where CO2 is insufficient, mitochondria disappear from tissues.

Under a microscope, you can see the Golgi apparatus, which is unique to eukaryotes. It was first discovered in nerve cells by the Italian scientist Camillo Golgi in 1898. This organelle plays the role of a cleaner, that is, it removes all metabolic products from the cell.

The Golgi apparatus has a disc-shaped shape, which consists of dense membrane cisterns connected by vesicles.

The functions of the Golgi apparatus are quite diverse:

participation in secretory processes;
formation of lysosomes;
delivery of metabolic products to the cell wall.

The earliest inhabitants of the Earth convincingly proved that, despite the absence of many cellular organelles, they are quite viable. Nature has given nuclear organisms a nucleus, mitochondria, and the Golgi apparatus, but this does not mean at all that small bacteria will give them their place in the sun.

Features of the structure:

The shape of the cells is varied, the sizes range from 5 to 100 microns.
Cells have similar chemical composition and metabolism.
Cells are divided by a system of membranes into compartments.
The genetic material is concentrated mainly in chromosomes, which have a complex structure and are formed by DNA strands and histone protein molecules.
The cytoplasm contains membrane organelles and centrioles.
Cell division is mitotic.

1. Nuclear envelope;

2. Karyoplasm;

3. Chromatin;

4. Nucleolus.

The shape of the nucleus depends on the shape of the cell itself and the functions it performs.

The size of the nucleus also mainly depends on the size of the cell.

Nuclear-cytoplasmic index – ratio of the volumes of the nucleus and cytoplasm. A change in this ratio is one of the causes of cell division or metabolic disorders.

Nuclear envelope the interphase core consists of two elementary membranes (outer and inner); between them there is a perinuclear space, which is connected through the channels of the endoplasmic reticulum to different parts of the cytoplasm. Both nuclear membranes are permeated at times, through which selective exchange of substances occurs between the nucleus and the cytoplasm. The inside of the nuclear membrane is covered with a protein mesh - nuclear lamina, which determines the shape and volume of the nucleus. Toward the nuclear lamina telomeric regions join chromatin threads. Microfilments form the inner core of the nucleus. The internal “skeleton” of the nucleus is of great importance for ensuring the orderly flow of basic processes transcription, replication, processing. The outside of the core is also covered microfilaments, which are elements cell cytoskeleton. The outer nuclear membrane has on its surface ribosomes and associated with membranes endoplasmic reticulum. The nuclear envelope has selective permeability. The flow of substances is regulated by the specific features of membrane proteins and nuclear pores (from 1000 to 10000).

Main functions of the nuclear membrane.

1. Formation of a cell compartment where the genetic material is concentrated and conditions are created for its preservation and doubling.

2. Separation of the contents of the nucleus from the cytoplasm.

3. Maintaining the shape and volume of the core.

Chromatin

The genetic material in the interphase nucleus is in the form

Nucleoli are fragmented at the beginning of cell division and restored after its completion. In the nucleoli there are 3 plots:

1. Fibrillar;

2. Granular;

3. Lightly colored.

- Fibrillar region of the nucleolus consists of strands of RNA. This is the site of active synthesis of ribosomal RNA on rRNA genes along the DNA molecule of decondensed chromatin.

- Granular area consists of RNA particles similar to ribosomes in the cytoplasm. It is the site where RNA and ribosomal proteins combine to form mature small and large ribosomal subunits.

- Lightly colored area The nucleolus contains DNA (inactive) that is not transcribed.

Main functions of nucleoli:

Synthesis of ribosomal RNA.
Formation of ribosomal subunits.

KERNEL FUNCTIONS:

1. Storage and transmission of hereditary information;

2. Regulation of all cell vital processes;

3. DNA repair;

4. Synthesis of all types of RNA;

5. Formation of ribosomes;

6. Implementation of hereditary information by regulating protein synthesis.

CHROMOSOMES.

1. Heterochromatin - strong spiralized and genetically inactive, revealed in the form of strongly colored dark areas of the nucleus.

2. Euchromatin – low condensed, genetically active, is detected in the form of light areas of the nucleus.

Chemical composition of chromosomes :

1. DNA – 40%

2. Basic or histone proteins – 40%

3. Non-histone (acidic or neutral) – 20%

4. Traces of RNA, lipids, polysaccharides, metal ions.