A branch of biology that studies the structure of the cell. All about the cell. The cage is

Biology- the science of living systems, laws and mechanisms of their emergence, existence and development.

The existing wildlife has passed a long, multi-stage path of historical development. The elementary structural unit of biological systems is the cell.

For the first time, cells were seen and described with a microscope in 1665 by R. Hooke. In 1839 T. Schwann and M. Schleiden created the cellular theory, according to which cells are the basis of living things. In 1858 R. Virkhov supplemented the cellular theory with the provision that every cell comes from another cell as a result of division.

Cells are characterized by physical and chemical properties, size, shape.

Cells are divided into prokaryotic and eukaryotic. Prokaryotic cells are more ancient (originated about 3-3.5 billion years ago) and have a simpler structure. They form prokaryotic organisms (bacteria, blue-green algae). Eukaryotic cells arose later (about 1-1.4 billion years ago), have a more complex structure and form unicellular and multicellular eukaryotic organisms (plants, fungi, animals).

Viruses constitute a special group of the smallest organisms that do not have a cellular structure. They occupy a borderline state between living biological systems and nonliving ones, and apparently originated from cellular organisms. The study of the morphological and functional characteristics of various bacteria and viruses is an important point for understanding their participation in the occurrence and development of human dental diseases.

Topic 1.1. Cellular and non-cellular levels of organization of biological systems

Goal.Know the main modern methods of studying cells. Know and be able to analyze the structure of cellular and non-cellular organisms by light or electron microscopy. Have an idea of \u200b\u200bthe physical and chemical properties of cells, the functions of their structures.

Assignment for students

Work 1. Methods for studying cells

Examine and rewrite the table in the notebook.

Method name	Their characteristics
1. Light microscopy	Study of cells under a light microscope based on cytochemical, histochemical, immunochemical and other studies. In this case, certain substances (for example, glycogen, lipids), chemical groups (for example, aldehyde, amino groups) or substances marked with specific antibodies are detected
2. Electron microscopy	Transmissive (transmission) electron microscopy is based on the passage of an electron beam emitted by an electron gun through cellular structures with an inhomogeneous electron density, which creates a planar image of an object on a fluorescent screen. Scanning (raster) electron microscopy is based on scanning the surface of the object under study with an electron beam
3. Polarizing microscopy	Study of structures based on refraction. A polarized light beam directed at an object is passed through an analyzer located between the objective and the eyepiece, which determines, depending on the spatial arrangement of molecules in the object, the nature of the deviation of the plane of polarization of light

The end of the table.

Method name Their characteristics

4. Fluorescence microscopy	The study of the ability of substances to emit visible light when an object is illuminated with ultraviolet rays (autofluorescence) or when stained with fluorescent dyes that bind to various structures or cell substances. For example, acridine orange, binding with DNA, gives a yellow-green glow, and with RNA - a red-orange
5. Tissue culture	Cells are preliminarily isolated from organs and tissues and cultured in special devices under sterile conditions using nutrient media and a certain gas composition. Tissue culture is used for cytological, pharmacological, toxicological, microbiological, genetic research, for the purposes of biotechnology and bioengineering
6. X-ray structural analysis	Study of the atomic structure of substances using X-ray diffraction. This determines the kind of atoms, their location in the structure of crystals, liquids, molecules

Work 2. The chemical composition of the cell

Examine and rewrite the table.

Work 3. Molecular organization of the biological membrane

(according to B. Albert, 1994) Study the fig. 1 3D view of the membrane. Note that lipids in the membrane form a bilayer (represented by phospholipids, cholesterol and glycolipids). Proteins are immersed in the lipid bilayer, there are fewer of them, the molecules are larger. Note that proteins can move around in lipids and they are the ones that mainly determine the specifics of membrane functions.

Work 4. The structure of bacteria

Examine fig. 2 the structure of a prokaryotic (bacterial) cell.

Figure: one.Biological membrane structure:

1 - lipid bilayer; 2 - protein molecule; 3 - lipid molecule

Figure: 2.The structure of a prokaryotic cell:

1 - flagellum; 2 - ribosomes; 3 - spare nutrients; 4 - capsule; 5 - plasma membrane; 6 - circular DNA molecule (nucleoid); 7 - cell wall; 8 - mesosome; 9 - cytoplasm; 10 - thylakoids (photosynthetic membranes)

Work 5. The structure of the animal cell

Study on microslides and in fig. 3 and 4 the structure of the animal cell, the inclusion of glycogen and fat. Sketch in some cells.

Figure: 3.Animal cell structure:

1 - cell shell; 2 - cytoplasm; 3 - core

Figure: 4.Inclusions of glycogen in epithelial cells: 1 - inclusion of glycogen in the cytoplasm of cells

A. The structure of the cells of the stratified squamous keratinizing epithelium of the mucous membrane of the hard palate of a person. Staining with hematoxylin - eosin (according to L.I.Falin, 1963).

B. Inclusions of glycogen in the cytoplasm of epithelial cells of the mucous membrane of the human lip. PAS-reaction (according to L.I. Falin, 1963).

B. Inclusion of fat in the cytoplasm of liver cells. Osmium staining. Examine the liver cells under high power microscope.

Find fatty inclusions in the cytoplasm in the form of round black drops of various sizes. Sketch in some cells with fat inclusions.

Designate: 1 - cell shell; 2 - core; 3 - cytoplasm with fatty inclusions.

Work 6. The structure of the surface apparatus of the animal cell(according to A.A. Zavarzin, 1982) Study the fig. 5 and sketch the molecular structure of the surface apparatus.

Figure: 5.The structure of the surface structure of an animal cell: 1 - surface apparatus of the cell; 2 - supramembrane structures (glycocalyx); 3 - plasma membrane; 4 - submembrane structures (microfilm and microtubules); 5 - bilipid layer; 6 - integral protein; 7 - semi-integral proteins; 8 - tunnel protein; 9 - surface protein; 10, 11 - glycoproteins and glycolipids of the glycocalyx

Work 7. Organelles of eukaryotic cells

Complete the table indicating the functions of the listed organelles.

Work 8. Ultramicroscopic structure of animal and plant cells

Examine on electronograms, according to Fig. 6 the structure of eukaryotic cells.

Figure: 6.Eukaryotic cell structure:

a - animal origin; b - of plant origin; 1 - nucleus with chromatin and nucleolus; 2 - plasma membrane; 3 - cell wall; 4 - plasmodesmata; 5 - granular endoplasmic reticulum; 6 - smooth endoplasmic reticulum; 7 - formed pinocytic vacuoles; 8 - lamellar complex; 9 - lysosomes; 10 - fatty inclusions; 11 - centrosome; 12 - mitochondria; 13 - polyribosomes; 14 - vacuole; 15 - chloroplast

Work 9. Comparative characteristics of prokaryotic and eukaryotic cells

Examine and rewrite the table.

Characteristics	Prokaryotic cells	Eukaryotic cells
Surface cell apparatus: Supramembrane structures; Plasma membrane; Submembrane structures	Formed by the cell wall, contain a reinforcing material - murein. Outside the cell wall, a number of bacteria have a capsule There is. Forms invaginations into the cytoplasm - mesosomes and thylakoids Not expressed	In plant cells, they are formed by a cell wall containing cellulose, and in animal cells, by a glycocalyx, consisting of glycolipid and glycoprotein molecules Form a supporting-contractile system consisting of microfibrils and microtubules
Organelles of the cytoplasm	Ribosomes	Endoplasmic reticulum, centrosome, mitochondria, lamellar complex, ribosomes, lysosomes. Plant cells have vacuole and plastids
Nuclear apparatus	The kernel is missing. A nucleoid is one annular chromosome located in the cytoplasm. Consists of DNA and small amounts of proteins	The nucleus has a two-membrane membrane, karyoplasm, chromatin (chromosomes), nucleoli. Chromosomes are made up of DNA and proteins

Work 10. The structure of the virus

Examine fig. 7 the structure of a bacteriophage and its electron micrograph (after N. Green, 1990). Draw a diagram of the structure of the virus, indicate its structure.

Figure: 7.Virus structure:

a - the structure of the bacteriophage; b - electron micrograph of a bacteriophage; 1 - virus head; 2 - collar; 3 - rod; 4 - cover; 5 - basal plate with spines and processes

Work 11. Structural features: DNA and RNA-containing animal viruses(according to A.P. Korotyaev, 1998) Examine fig. 8 and sketch a selection of viruses of various shapes and sizes.

Figure: 8.DNA- (a) and RNA-containing (b) viruses

Self-study questions

1. What are the main properties of biological systems?

2. What levels of organization of biological systems are evolutionarily determined?

3. What are the main provisions of the cell theory of T. Schwann, M. Schleiden, R. Virchow? The current state of cell theory?

4. What are the main physical and chemical properties of a cell?

5. What is the current understanding of the molecular organization of a biological membrane and its functions?

6. How are prokaryotic cells arranged?

7. How are eukaryotic cells arranged?

8. How do viruses work?

9. What are the hypotheses of the origin of eukaryotic cells?

Test tasks

1. ORGANELLS OF PROKARYOTIC CELLS ARE:

1. Mitochondria

2. Ribosomes

3. Centrosome

4. Lamellar complex

2. RESISTANCE OF CERTAIN SPECIES OF BACTERIA

TO LYSOCYME OF SALIVA AND TEARS EXPLAINED BY THE PRESENCE

IN THEIR CELL WALL:

2. Soft lipids

3. Mureina

4. Polysaccharides

3. DISEASE PROPERTIES OF CERTAIN BACTERIA SPECIES ARE DUE TO THE PRESENCE IN THEIR CELL WALL:

1. Polysaccharides. mureina

2. Polysaccharides. lipids

3. Polysaccharides. capsular polysaccharides

4. Polysaccharides. proteins

4. ACCORDING TO THE MODERN CELLULAR THEORY, THE CELL IS

1. Open

2. Closed

3. Elementary

4. Universal

5. Holistic

5. THE PROPERTIES OF BIOLOGICAL SYSTEMS ARE:

1. Integrity and discreteness

2. Reproduction

3. Metabolism

4. Low entropy (negentropy)

5. Heredity and variability

6. High entropy

6. EVOLUTIONARY LEVELS OF ORGANIZATION OF BIOLOGICAL SYSTEMS ARE:

1. Molecular genetic

2. Cellular

3. Fabric

4. Population-specific

5. Biogeocenotic

7. BIOLOGICAL MEMBRANES OF CELLS PROVIDE:

1. Compartment

2. Barrier function

3. Formation of ribosomes and polisomes

4. Transport of substances

5. Front desk

Establish correspondence.

8. METHODS OF STUDYING CELLS:

1. Light microscopy

2. Polarizing microscopy

3. Fluorescence microscopy

4. Electron microscopy

5. X-ray structural analysis

6. Tissue culture

CHARACTERISTIC OF THE METHOD:

a) Study of living cells in a nutrient medium

b) Study of the configuration of biopolymer molecules

c) Study of cellular structures based on their scattering of an electron beam

d) Study of cells in a light microscope

e) Study of cells stained with fluorochrome substances

f) Study of cells based on birefringence)

9. TYPE OF CELL:

1. Prokaryotic

2. Eukaryotic

SURFACE APPARATUS CHARACTERISTICS:

a) The cell wall contains murein

b) The cell wall contains cellulose

c) Plasma membrane

d) Glycocalyx contains lipoproteins and glycolipids

e) Submembrane structures - microfibrils and microtubules.

10. ORGANELLS OF CELLS

EURARIOT:

1. Smooth endoplasmic

network (EPS)

2. Ribosomes

3. Mitochondria

4. Centrosome

5. Lamellar complex

6. Lysosomes

THEIR FUNCTIONS:

a) Protein synthesis

b) Synthesis of carbohydrates and lipids

c) Cell division

d) Energy generation

e) Intracellular digestion of substances

f) Isolation of substances from the cell

Literature

Main

Book. 1. - S. 18-21, 24-51, 54-55.

Pehov A.P.

Additional

Albert B., Braid D.and other Molecular biology of the cell. - M .: Mir, 1994 .-- T. 1.

Gilbert S.Developmental biology. - M .: Mir, 1995 .-- T. 1-3. Green N, Stout U., Taylor D.Biology. - M .: Mir, 1990 .-- T. 1. Zavarzin A.A., Kharazova A.D.Fundamentals of General Cytology. - L .:

Publishing house of Leningrad State University, 1982.

Topic 1.2. Organization of hereditary material in pro- and eukaryotes. Implementation of genetic

information and its regulation

Goal.To know the molecular structure and properties of nucleic acids, chromosomes, stages of protein biosynthesis, principles of regulation of gene activity. Be able to identify DNA in cell nuclei using the Feelgen reaction.

Assignment for students

Work 1. DNA in cell nuclei

On a continuous specimen under a high magnification microscope, examine the DNA detected using the Felgen reaction in the nuclei of the epithelial cells of the oral mucosa.

Sketch a few nuclei with purple-magenta DNA.

Work 2. Molecular structure of eukaryotic DNA

Consider fig. 1. Sketch the structure of the secondary (2) structure

Figure: one.Eukaryotic DNA structure.

DNA structures: 1 - primary; 2 - secondary; 3 - tertiary.

A - adenine; G - guanine - purine nitrogenous bases; C - cytosine; T - thymine-pyrimidine nitrogenous bases; D - deoxyribose; F - the remainder of phosphoric acid; H - nucleotide

Work 3. Structural and functional organization of DNA in pro- and eukaryotes

Examine the tables, rewrite them in your workbook.

Signs	Prokaryotes	Eukaryotes
Number of genes	4 thous. (E. coli)	About 30 thousand (people)
DNA amount	4 million base pairs	3-7 billion base pairs
Coding sequences
DNA link with histones	Is absent	Forms nucleosomes
DNA packing	Circular, contains 100 loops of 40 thousand base pairs	Linear with ends closed in telomeres, has 4 levels of spiralization
Number of replicons
Actively working areas	More than 90% of genes	Less than 10% of genes
Processing	Is absent	Carried out during the transition of pre-mRNA from the nucleus to the cytoplasm
Regulation of transcription	Operon	Complex cascading

Work 4. Organization of hereditary material in prokaryotes (nucleoid)

Consider fig. 2 and notice the looping of the DNA.

Figure: 2.DNA folding in prokaryotic nucleoid:

1 - circular DNA molecule; 2 - DNA folding in the form of loops; 3 - proteins that bind DNA loops

Work 5. Levels of interphase chromatin organization

Consider in fig. 3 levels of organization of hereditary material in eukaryotes.

Figure: 3.Scheme of different levels of chromatin compaction: a - nucleosome thread; b - microfibril; c - interphase chromonema; d - molecular organization of the nucleosome strand: 1 - nucleosome; 2 - DNA; 3 - histones H2A, H2B, H3 and H4; 4 - histone H1

Work 6. Protein biosynthesis in prokaryotes and eukaryotes

Study and sketch the process of protein biosynthesis according to scheme 1.

Scheme 1.Protein biosynthesis in prokaryotes (a) and eukaryotes (b)

Work 7. Transcription and processing in eukaryotes

Learn transcription and processing in fig. 4.

Figure: 4.Transcription and processing in eukaryotes:

1 - DNA; 2 - pre-mRNA; 3 - RNA polymerase; 4 - codogenic DNA chain; 5 - exons; 6 - introns; 7 - mature mRNA; T - terminator; CEP and poly-A - terminal nucleotide sequences; TAC and AUG - initiator triplets

Work 8. Broadcast. Stages of the ribosomal cycle

Examine and sketch in fig. 5 broadcast process.

Figure: 5.Broadcast process:

1 - small subunit of the ribosome; 2 - large subunit of the ribosome; 3 - aminoacyl (A) center; 4 - peptidyl (P) center; 5 - AUG-initiator mRNA triplet; 6 - mRNA terminator; 7 - initiator tRNA; 8 - amino acids of the forming polypeptide; 9 - cap

Work 9. Regulation of gene activity in prokaryotes (Jacob-Monod scheme)

View and sketch a picture of the regulation of protein synthesis by induction and repression (Figure 6).

Figure: 6.Regulation of protein synthesis by induction (a, b) and repression (c, d): a - structural genes of the operon are blocked; b - derepression of genes by an inducer; c - with an insufficient amount of the final product (corepressor), the operon is derepressed, and with an excess amount, it is blocked (d)

Work 10. Basic principles of regulation of gene activity in eukaryotes

Study and rewrite.

1. In eukaryotes, the operon organization of genes has not been established, since the genes that determine the synthesis of enzymes of one chain of biochemical reactions can be scattered in the genome and, as in prokaryotes, do not have a single regulatory system (regulator gene, promoter, operator, etc. .).

2. Regulation of transcription in eukaryotes is combinational, i.e. the activity of each gene is regulated by a large number of regulatory genes.

3. Many eukaryotic genes have several zones in their DNA that are recognized by different proteins.

4. In eukaryotes, there are regulatory proteins that control the work of other regulatory proteins, and their action can be characterized by pleiotropic effect.

5. In the regulation of eukaryotic gene expression, an important role is played by the genes enhancers (increase transcription) and silencers (inhibit transcription).

6. Hormones are involved in the regulation of transcription, and chromosome histones are involved in gene activity.

7. Regulation of gene expression is carried out at all stages of the realization of hereditary information.

Self-study questions

1. What are the features of the organization of hereditary material in pro- and eukaryotes?

2. What is the molecular organization and function of nucleic acids?

3. What is a gene? What definition of a gene do you think is more accurate?

4. What are the structural features of genes in pro- and eukaryotes?

5. What is the genetic code and what are its properties?

6. What are the main stages of protein biosynthesis, what is their essence?

7. What are the mechanisms of regulation of gene activity in prokaryotes (Jacob-Monod scheme)?

8. What are the basic principles of regulation of gene activity in eukaryotes?

Test tasks

Choose one correct answer.

1. THE ELEMENTARY UNIT OF THE HERITAGE MATERIAL FUNCTION IS:

2. TRANSCRIPTION IS CARRIED OUT BY ENZYM

1.DNA polymerase

2. RNA polymerase

3. Helicase

3. MULTIGENIC FAMILIES AND COMPLEXES IN THE GENOME

1. Prokaryotes

3. Eukaryotes

Choose several correct answers.

4. PROPERTIES OF DNA AS HEREDITARY SUBSTANCES ARE:

1. Chemical stability

2. Replication

3. Reparation

4. Ability to broadcast

5. PROTEIN BIOSYNTHESIS OCCURS WITH THE PARTICIPATION OF ORGANELLES:

1. Lysosomes

2. Smooth EPS

3. Ribosomes

4. Polysomes

6. FEATURES OF REGULATION OF GENE EXPRESSION IN EURARIOTA ARE:

1. Lack of operon organization of genes

2. The presence of the operon organization of genes

3. The presence of combination regulation of transcription

4. Regulation of gene expression at all stages of the implementation of genetic information

Establish correspondence.

7. DNA TRIPLETS:

MRNA TRIPLETS:

Establish the correct sequence.

8. DNA PACKAGING IN THE EUKARIOT CHROMOSOME:

1. Chromonema

2. Chromatid

3. Nucleosomal filament

4. Microfibril

9. PROTEIN BIOSYNTHESIS IN EURARIOT:

1. Broadcast

2. Transcription

3. Processing

4. Post-broadcast

10. REGULATION OF GENE EXPRESSION IN PROCARIOTAS

(SCHEME OF JAKOBE-MONO):

1. Reading information from structural genes

2. Formation of the inductor-repressor complex

3. Entry of the inducer into the cytoplasm of the prokaryote

4. Freeing the operator from the repressor

5. Formation of polycistronic transcript

6. Synthesis of individual peptides

Literature

Main

Biology / Ed. V.N. Yarygin. - M .: Higher school, 2001. - Book. 1. - S. 65-138, 147-152, 163-171.

Pehov A.P.Biology with general genetics. - M .: Publishing house of RUDN, 1993. - S. 95-112, 141-154, 166-171.

Additional

Albert B.and other Molecular biology of the cell. - M .: Mir, 1994. -

Gilbert S.Developmental biology. - M .: Mir, 1994. Zhimulev I.F.General and molecular genetics. - N .: Siberian University Publishing House, 2003.

Topic 1.3. Reproduction at the cellular level

Goal.Know the life cycle of cells, the processes occurring in the mitotic cycle and during terminal differentiation. Have an understanding of the mechanisms of regulation of the cell cycle. To be able to determine the phases of mitosis on micropreparations and calculate the mitotic coefficient. Know the essence and biological significance of meiosis.

Assignment for students

Job 1. Cell cycle

The body's somatic cells are formed as a result of mitosis. In the future, three variants of the life path (cycle) of cells are possible:

1. Cells prepare for division and end their life with mitosis (mitotic cycle).

2. Cells differentiate, function and die.

3. The cells pass into the G 0 period, in which they can be from several hours to many years. Under certain conditions, they can pass from this period into the mitotic cycle or terminal differentiation.

Examine and sketch the diagram of the life cycle of cells shown in Fig. one.

Figure: one.Cell life cycle:

G 1 - presynthetic period; S - synthetic period; G 2 - post-synthetic period;

MC(mitotic cycle) \u003d G 1 + S + G 2 + mitosis;

G 0 - the period of the cell cycle, which includes:

Cells of the proliferative pool of slowly renewing tissues;

Cells released from the MC for DNA repair;

Cells unable to pass MC due to nutritional deficiencies or growth factors;

Reserve and stem cells; n - haploid set of chromosomes;

c - single set of DNA

Work 2. Doubling of chromosomes and DNA replication in eukaryotes

Doubling of DNA and chromosomes occurs in the S-period of the mitotic cycle.

DNA replication begins simultaneously in many places - points of initiation (Fig. 2a). There is an attachment of a complex of enzymes ("replicative machine"), DNA is freed from histones and unwinds, a replication eye is formed (Fig. 2b). Separation of the original template and synthesis of new daughter DNA strands in the eye occur simultaneously in both directions in replication forks (Fig. 2c). After DNA duplication, histones bind to them, and the chromosome becomes double, consisting of two chromatids, which are connected in the centromere region (Fig. 2d).

Figure: 2a.The beginning of DNA replication in the chromosome

Figure: 2b.Replication eyes and replication forks

Figure: 2c.DNA synthesis in a replication fork:

1 - template DNA chains; 2 - enzyme helicase, which separates the chains of the template DNA; 3 - DSB proteins that prevent the reunification of DNA strands; 4 - primase; 5 - RNA primer (synthesized by RNA polymerase - primase); 6 - DNA polymerase synthesizing daughter chains; 7 - leading daughter DNA strand; 8 - ligase connecting the Okazaki fragments of the lagging DNA strand; 9 - fragment of Okazaki (150-200 nucleotides); 10 - topoisomerase

Figure: 2d.Completion of DNA and chromosome duplication

Examine the scheme of DNA replication and chromosome duplication, shown in Fig. 2a-2d. Sketch the rice. 2c.

Work 3. Mitosis of plant cells

Examine the microscope of the onion root under a high magnification microscope. Find cells that are in interphase and different phases of mitosis. Sketch and label:

I - stages of mitosis: 1 - prophase;

2 - metaphase;

3 - anaphase;

4 - telophase;

II - interphase (non-dividing cell).

Work 4. Mitosis of human cells

Examine at low magnification a cytogenetic preparation of human blood lymphocytes. Find a cell in mitosis. Switch to high magnification by placing an immersion lens (x90). Examine the metaphase plate on the preparation. Pay attention to the structure of human chromosomes, their sizes, the location of the centromere, the number of chromatids in the metaphase chromosome. Determine the set of chromosomes, find homologous chromosomes. Draw metaphase chromosomes with different centromere locations.

Work 5. Determination of the mitotic coefficient

On onion root microslides, count the number of dividing and non-dividing cells in several fields of view (about 1000 cells). Determine the mitotic coefficient using the formula:

Number of mitoses

MC is expressed in ppm (% o).

Work 6. Types of tissues depending on the level of cell proliferation

Stable - all cells are in a state of irreversible differentiation. The death of some of the cells during the life of the organism leads to a decrease in the total number of cells in the tissue.

Growing - the number of cells in the tissue increases, since the proportion of cells entering the mitotic cycle exceeds the proportion of cells entering differentiation.

Renewable - cells multiply, but the total number of cells remains constant, since half of the cells go into irreversible differentiation and die.

Examine and rewrite the table.

Type of fabric	Average proliferation parameters
Type of fabric	P c,% T, MK hours, %%
*Rapidly renewing fabrics:* red bone marrow; epithelium of the mouth, tongue, esophagus, stomach and small intestine; skin epidermis
*Slowly renewing tissues:* liver parenchyma, kidney parenchyma		Not defined. Cell renewal rate - about 6 months
*Stable fabrics:* tooth enamel, cardiomyocytes, nervous tissue	Not determined
*Growing:* embryonic, regenerating, tumor		6-10 and more

Note:P c - proliferative pool; T is the duration of the mitotic cycle; MK - mitotic coefficient. Proliferative pool - the proportion of cells that are in all phases of the mitotic cycle and in the G 0 pool, capable of reproduction.

Work 7. Stem cells. Their biological and medical significance

Stem cells- These are cells that retain the ability to reproduce throughout the entire life of the organism. In the embryonic period, they are needed for the development of organs and tissues, in the postembryonic period - for the growth of the organism, tissue renewal, regeneration and vegetative reproduction.

Examine the table.

Stem cell type Characteristics Value

Totipotent	Capable of giving rise to any type of cell (blastomeres in the early stages of cleavage)	The development of the organism during sexual reproduction begins from embryonic totipotent cells. Somatic ones give rise to new organisms during vegetative reproduction
Polypotent (pluripotent)	Capable of producing different types of cells (germ layer cells; red bone marrow cells)	Formation of organs and tissues of a developing organism. Necessary for the renewal or regeneration of tissues that do not have their own stem cells - erythrocytes and leukocytes, neurons, cardiomyocytes
Unipotent	When multiplying, they form cells of only one type (epithelium of the oral cavity, salivary glands)	A source of cells for the growth, renewal and regeneration of organs
Reconstructed embryonic	Isolated embryonic stem cells in which the composition of genes has been modified by genetic engineering	Use in medicine allows you to grow organs and tissues with desired properties. Their use for reproductive cloning is a source of genetically modified organisms

The use of stem cells in medicine and dentistry

Improving the methods of isolating stem cells, studying the factors regulating their growth and differentiation, opens up wide possibilities for the use of such cells in medicine. Stem cells taken from the umbilical cord blood or from other tissues can replace your own damaged cells in any organs without fear of rejection. The use of embryonic cells, therapeutic cloning and the use of genetic engineering methods will make it possible to grow organs and tissues and obtain available material for transplantation. At present, it is possible to obtain whole teeth or their individual tissues (enamel, pulp, and others) from stem cells in experimental animals. So, the embryos of the tooth, grown in mice from the cells of the dental papilla, after implantation in adult animals, instead of the removed incisors, took root and formed full-fledged teeth. In humans, from the stem cells of the pulp or apical tubercle of the extracted wisdom teeth, it was possible to grow roots and periodontal ligaments, on the basis of which the crown of the tooth was restored (using conventional methods of prosthetics so far). Thus, in the future, it is planned to obtain material for autotransplantation. The use of mesenchymal stem cells and composite materials has made it possible to develop implants for replacing bone defects in maxillofacial surgery. It should be noted that the use of stem cells is currently at the stage of experimental research or clinical trials. Their widespread introduction into practical medicine is a matter of the near future.

Work 8. Different directions of differentiation of cells of the oral cavity

Examine and sketch diagram 1.

Scheme 1.Directions of differentiation of cells in the oral cavity Work 9. Regulation of cell reproduction

In the renewing tissues, a constant number of cells is maintained as a result of self-regulation, carried out according to the principle of negative feedback. With a decrease in the number of cells, mechanisms that activate protooncogenes are activated. The induction of these genes leads to the synthesis of growth factors that provide mitogenic stimulation to cells located in G o-period, including stem cells. They multiply and increase in number. The excess of cells leads to repression of protooncogenes and activation of suppressor genes responsible for the synthesis of inhibitors of cell proliferation. Periodic fluctuations in the number of dividing cells, manifested in circadian rhythms of proliferation, allow achieving a state of dynamic equilibrium - the number of cells is maintained at the level required for a given tissue.

Study Scheme 2. Give examples of growth factors and inhibitors of cell division.

Scheme 2.Self-regulation of cell proliferation

Work 10. Comparative characteristics of normal cells and cells of malignant tumors

Mutations of protooncogenes or suppressor genes that regulate cell proliferation can occur spontaneously or under the action of carcinogenic factors. Protooncogenes are converted into oncogenes that do not respond to regulatory factors and form a large number of growth factors. Damage to suppressor genes does not allow to restrain excessive cell proliferation - a tumor appears. Tumor cells are characterized by genetic instability - new mutations appear in them, which further disrupt the regulation of cell proliferation. A benign tumor can transform into a malignant one.

Examine the table.

Options Normal cells Tumor cells

The end of the table.

Options	Normal cells	Tumor cells
Proliferative pool	Permanent for every fabric	Increases progressively
Intercellular contacts	Limit the increase in the number of cells during contact inhibition	Disrupted: no contact inhibition of proliferation
Cell membrane	Provides the ability to multiply cells in contact with the basement membrane or other supporting structures	Modified: Cells can multiply without contact with supporting structures
Cell adhesion	Normal	Reduced: cell detachment and metastasis is possible
Time characteristic	Unipodular daily rhythm of mitosis	Violation of the mitotic rhythm: bimodal, inverted, no rhythm
Spatial organization	Strictly defined	Violated due to loss of control of proliferation and changes in cell contacts
Cell division		A significant number of mitotic disorders, amitosis
Chromosome set	Strictly defined (karyotype)	Significant changes in the number and structure of chromosomes

Work 11. Meiosis, its features in comparison with mitosis

a) Under a high magnification microscope, examine a cross-sectional preparation of the roundworm uterus. Find first-order oocytes at meiotic stage 1.

Sketch and label:

1 - oocyte;

2 - cytoplasm;

3 - tetrad.

b) Using the materials of the textbook, lectures and visual aids, study the stages of reduction and equational divisions of meiosis. Note the differences between mitosis and meiosis. Fill the table.

Comparative characteristics of mitosis and meiosis

Self-study questions

1. What is the life cycle of cells?

2. What is a mitotic cycle, what periods does it consist of? What happens at different times in the mitotic cycle?

3. How are new cells formed? How does cell life end?

4. What molecular processes underlie the doubling of the DNA molecule? How does chromosome duplication occur?

5. Phases of mitosis. The biological essence and significance of mitosis.

6. What are polytenia, endomitosis and polyploidy?

7. What is the mitotic coefficient and how is it determined?

8. What types of tissues are distinguished depending on their mitotic activity? How are they characterized?

9. What is the difference between the life cycles of normal and tumor cells?

10. What are the mechanisms of regulation of cell division?

11. What are stem cells? Types of stem cells and their importance for dentistry.

12. Cell cycles and directions of differentiation during the formation of tissues of the organs of the human oral cavity.

13. What is the biological significance and essence of meiosis?

14. How does the set of chromosomes, chromatids and DNA change during meiosis?

15. What processes lead to the recombination of genetic material during meiosis?

Test tasks

Choose one correct answer.

1. CHROMOSOME DUALING TAKES PLACE IN THE PERIOD OF THE CELL CYCLE:

1. Presynthetic

2. Postsynthetic

3. Synthetic

5.G o-period

2. INCREASE IN THE NUMBER OF DNA MOLECULES IN CHROMOSOMES PROVIDES:

3. Endomitosis

5. Polities

3. STEM CELLS ARE CONSERVED FOR A PERIOD

CELL CYCLE:

5. In differentiation

4. IN MEIOSIS, DIVISION OF HOMOLOGICAL CHROMOSOMES

HAPPENS IN:

1. Prophase I

2. Metaphase I

3. Anaphase I

4. Metaphase II

5. Anaphase II

Choose several correct answers.

5. CONJUGATION OF HOMOLOGICAL CHROMOSOME IN MEIOSIS

REQUIRED FOR:

1. Doubling of chromosomes

2. Crossing over

3. Reparations

4. Amplification

5. Ordered arrangement of homologous chromosomes

6. RAPIDLY RENEWING FABRICS ARE:

1. Nervous

2. Intestinal epithelium

3. Liver parenchyma

4. Red bone marrow

5. Tooth enamel

6. Epithelium of the tongue

7. Embryonic tissue

Establish correspondence.

7. NUMBER OF CELLS:

1. Does not change

2. Increases

3. Decreases

a) Growing

b) Slowly updating

c) Rapidly updating

d) Stable

8. AFTER DIVISION:

3. Endomitosis

QUANTITY OF CHROMOSOME (n) AND DNA (s)

COMPOSITS IN THE CELL:

9. ENZYME:

1. Helicase

2. RNA polymerase

3.DNA polymerase

a) Synthesis of primers

b) Cutting out primers

c) Separation of DNA matrix strands

d) Stabilization of template DNA strands

e) Synthesis of daughter DNA strands

f) Stitching the Okazaki fragments

Establish the correct sequence.10. EVENTS DURING DNA REPLICATION:

1. Separation of DNA strands

2. Connecting fragments of Okazaki

3. Synthesis of primers

4. Removal of primers

5. Synthesis of Okazaki fragments

Literature

Main

Biology / Ed. V.N. Yarygin. - M .: Higher school, 2001. -

Book. 1. - S. 55-60, 72-79, 118-144, 200-207.

Pehov A.P.Biology and general genetics. - M .: Publishing house of RUDN University, 1993.-

S. 64-80, 107-112.

Additional

Zhimulev I.F.General and molecular genetics. - Novosibirsk: Publishing house of Novosibirsk University, 2002.

Lushnikov E.F., Abrosimov A.Yu.Cell death (apoptosis). - M .: Medicine, 2001.

Epifanova O.I.Lectures on the cell cycle. - M .: KMK, 2003.

(nuclear). Prokaryotic cells are simpler in structure, apparently, they arose in the process of evolution earlier. Eukaryotic cells are more complex and arose later. The cells that make up the human body are eukaryotic.

Despite the variety of forms, the organization of cells of all living organisms is subordinated to unified structural principles.

Prokaryotic cell

Eukaryotic cell

The structure of the eukaryotic cell

Surface complex of an animal cell

Consists of glycocalyx, plasmalemmas and the cortical layer of the cytoplasm located under it. The plasma membrane is also called the plasmalemma, the outer cell membrane. It is a biological membrane, about 10 nanometers thick. First of all, it provides a delimiting function in relation to the environment external to the cell. In addition, it performs a transport function. The cell does not spend energy to preserve the integrity of its membrane: the molecules are held according to the same principle by which fat molecules are held together - it is thermodynamically more advantageous for hydrophobic parts of molecules to be located in close proximity to each other. Glycocalyx is a molecule of oligosaccharides, polysaccharides, glycoproteins and glycolipids "anchored" in the plasma membrane. Glycocalyx performs receptor and marker functions. The plasma membrane of animal cells mainly consists of phospholipids and lipoproteins with embedded molecules of proteins, in particular, surface antigens and receptors. The cortical (adjacent to the plasma membrane) layer of the cytoplasm contains specific elements of the cytoskeleton - actin microfilaments ordered in a certain way. The main and most important function of the cortical layer (cortex) is pseudopodial reactions: ejection, attachment and contraction of pseudopodia. In this case, the microfilaments are rebuilt, lengthened or shortened. The shape of the cell also depends on the structure of the cytoskeleton of the cortical layer (for example, the presence of microvilli).

Cytoplasm structure

The liquid component of the cytoplasm is also called cytosol. Under a light microscope, it seemed that the cell was filled with something like a liquid plasma or sol, in which the nucleus and other organelles "float". This is not actually the case. The inner space of a eukaryotic cell is strictly ordered. The movement of organelles is coordinated with the help of specialized transport systems, the so-called microtubules, which serve as intracellular "roads" and special proteins dyneins and kinesins, which play the role of "engines". Individual protein molecules also do not diffuse freely throughout the intracellular space, but are directed to the necessary compartments using special signals on their surface, which are recognized by the cell transport systems.

Endoplasmic reticulum

In a eukaryotic cell, there is a system of membrane compartments (tubes and cisterns) passing into each other, which is called the endoplasmic reticulum (or the endoplasmic reticulum, EPR or EPS). That part of the ER, to the membranes of which ribosomes are attached, is referred to as granular (or rough) the endoplasmic reticulum, protein synthesis occurs on its membranes. Those compartments without ribosomes on their walls are referred to as smooth (or agranular) EPR, which takes part in lipid synthesis. The internal spaces of smooth and granular EPR are not isolated, but merge into each other and communicate with the lumen of the nuclear envelope.

Golgi apparatus

Core

Cytoskeleton

Centrioli

Mitochondria

Comparison of pro- and eukaryotic cells

The most important difference between eukaryotes and prokaryotes has long been considered the presence of a formed nucleus and membrane organelles. However, by the 1970s-1980s. it became clear that this is only a consequence of deeper differences in the organization of the cytoskeleton. For some time it was believed that the cytoskeleton is characteristic only of eukaryotes, but in the mid-1990s. proteins homologous to the main proteins of the eukaryotic cytoskeleton have also been found in bacteria.

It is the presence of a specifically arranged cytoskeleton that allows eukaryotes to create a system of mobile internal membrane organelles. In addition, the cytoskeleton allows endo- and exocytosis (as it is supposed, it is thanks to endocytosis that intracellular symbionts, including mitochondria and plastids, appeared in eukaryotic cells). Another important function of the eukaryotic cytoskeleton is to ensure the division of the nucleus (mitosis and meiosis) and the body (cytotomy) of the eukaryotic cell (the division of prokaryotic cells is easier to organize). Differences in the structure of the cytoskeleton also explain other differences between pro and eukaryotes - for example, the constancy and simplicity of the forms of prokaryotic cells and a significant variety of shape and the ability to change it in eukaryotic, as well as the relatively large size of the latter. Thus, the size of prokaryotic cells is on average 0.5-5 microns, the size of eukaryotic cells is on average from 10 to 50 microns. In addition, only among eukaryotes there are truly giant cells, such as massive eggs of sharks or ostriches (in a bird's egg, the entire yolk is one huge egg), neurons of large mammals, whose processes, strengthened by the cytoskeleton, can reach tens of centimeters in length.

Anaplasia

The destruction of the cellular structure (for example, in malignant tumors) is called anaplasia.

Cell discovery history

The first person to see the cells was the English scientist Robert Hooke (known to us thanks to Hooke's law). In a year, trying to understand why the cork tree floats so well, Hooke began to examine thin sections of the cork with his improved microscope. He discovered that the cork was divided into many tiny cells that reminded him of monastery cells, and he called these cells cells (in English cell means “cell, cell, cage”). In the year, the Dutch master Anton van Leeuwenhoek, with the help of a microscope, first saw in a drop of water "animals" - moving living organisms. Thus, by the beginning of the 18th century, scientists knew that under high magnification, plants have a cellular structure, and they saw some organisms, which were later called unicellular. However, the cellular theory of the structure of organisms was formed only by the middle of the 19th century, after more powerful microscopes appeared and methods for fixing and staining cells were developed. One of its founders was Rudolf Virchow, but there were a number of mistakes in his ideas: for example, he assumed that cells are weakly connected to each other and each exists "on its own". Only later was it possible to prove the integrity of the cellular system.

Links

Molecular Biology Of The Cell, 4th Edition, 2002 - Molecular Biology Textbook in English
Cytology and Genetics (0564-3783) publishes articles in Russian, Ukrainian and English languages \u200b\u200bof the author's choice, translated into English (0095-4527)

Wikimedia Foundation. 2010.

See what "Cell (biology)" is in other dictionaries:

BIOLOGY - BIOLOGY. Contents: I. History of Biology .............. 424 Vitalism and Machinism. The emergence of empirical sciences in the XVI XVIII centuries. The emergence and development of evolutionary theory. The development of physiology in the XIX century. Development of cellular learning. Results of the XIX century ... Big medical encyclopedia

- (cellula, cytus), the basic structurally functional unit of all living organisms, an elementary living system. It can exist as a department. organism (bacteria, protozoa, some algae and fungi) or as part of the tissues of multicellular animals, ... ... Biological encyclopedic dictionary

The cells of aerobic spore-forming bacteria are rod-shaped and, in comparison with non-spore-bearing bacteria, are usually larger in size. Vegetative forms of spore-bearing bacteria have a weaker active movement, although they ... ... Biological encyclopedia

This term has other meanings, see Cell (disambiguation). Human blood cells (SEM) ... Wikipedia

All living things and organisms do not consist of cells: plants, fungi, bacteria, animals, people. Despite its minimal size, the cell performs all the functions of the whole organism. Complex processes take place inside it, on which the vitality of the body and the work of its organs depend.

In contact with

Structural features

Scientists are studying structural features of the cell and the principles of its work. It is possible to examine in detail the features of the cell structure only with the help of a powerful microscope.

All our tissues - skin, bones, internal organs are composed of cells that are building material, come in different shapes and sizes, each variety performs a specific function, but the main features of their structure are similar.

Let's first find out what lies behind structural organization of cells... In the course of the studies conducted, scientists have established that the cellular foundation is membrane principle. It turns out that all cells are formed from membranes, which consist of a double layer of phospholipids, into which protein molecules are immersed from the outside and inside.

What property is characteristic of all types of cells: the same structure, as well as functionality - regulation of the metabolic process, the use of its own genetic material (presence and RNA), the receipt and consumption of energy.

The structural organization of the cell is based on the following elements that perform a specific function:

membrane - the cell membrane consists of fats and proteins. Its main task is to separate the substances inside from the external environment. The structure is semi-permeable: it is also capable of transmitting carbon monoxide;
core - the central region and the main component, separated from other elements by a membrane. It is inside the nucleus that information about growth and development, genetic material, presented in the form of DNA molecules that make up the composition, is located;
cytoplasm Is a liquid substance that forms an internal environment where various vital processes take place, contains a lot of important components.

What does the cellular content consist of, what are the functions of the cytoplasm and its main components:

Ribosome - the most important organoid, which is necessary for the processes of biosynthesis of proteins from amino acids, proteins perform a huge number of vital tasks.
Mitochondria - another component located inside the cytoplasm. It can be described in one word combination - an energy source. Their function is to provide components with power for further energy production.
Golgi apparatus consists of 5 - 8 bags, which are interconnected. The main task of this apparatus is to transfer proteins to other parts of the cell to provide energy potential.
Damaged elements are cleaned lysosomes.
Transport is carried out endoplasmic reticulum, along which proteins move molecules of useful substances.
Centrioli responsible for reproduction.

Core

Since it is a cell center, therefore, special attention should be paid to its structure and functions. This component is an essential element for all cells: it contains hereditary characteristics. Without the nucleus, the processes of reproduction and transmission of genetic information would become impossible. Look at the figure showing the structure of the nucleus.

The nuclear envelope, which is highlighted in lilac color, lets the substances inside and releases them back through the pores - small holes.
Plasma is a viscous substance, it contains all the other nuclear components.
the core is located in the very center, has the shape of a sphere. Its main function is the formation of new ribosomes.
If you look at the central part of the cell in section, you can see subtle blue weaves - chromatin, the main substance, which consists of a complex of proteins and long DNA strands that carry the necessary information.

Cell membrane

Let's take a closer look at the work, structure and function of this component. Below is a table that clearly shows the importance of the outer shell.

Chloroplasts

This is another overriding component. But why chloroplasts were not mentioned before, you ask. Because this component is found only in plant cells.The main difference between animals and plants lies in the way of feeding: in animals it is heterotrophic, and in plants it is autotrophic. This means that animals are not able to create, that is, synthesize organic substances from inorganic ones - they feed on ready-made organic substances. Plants, on the other hand, are capable of carrying out the process of photosynthesis and contain special components - chloroplasts. These are green plastids containing chlorophyll. With its participation, the energy of light is converted into the energy of chemical bonds of organic substances.

Interesting!Chloroplasts in large volumes are concentrated mainly in the aerial part of plants - green fruits and leaves.

If you are asked the question: name an important feature of the structure of organic compounds of the cell, then the answer can be given as follows.

many of them contain carbon atoms that have different chemical and physical properties, and are also capable of bonding with each other;
are carriers, active participants in various processes taking place in organisms, or are their products. This refers to hormones, various enzymes, vitamins;
can form chains and rings, which provides a variety of connections;
destroyed by heating and interaction with oxygen;
atoms in the composition of molecules combine with each other using covalent bonds, do not decompose into ions and therefore slowly interact, reactions between substances take a very long time - for several hours or even days.

Chloroplast structure

Fabrics

Cells can exist one at a time, as in unicellular organisms, but most often they are combined into groups of their own kind and form various tissue structures that make up the organism. There are several types of tissues in the human body:

epithelial - concentrated on the surface of the skin, organs, elements of the digestive tract and the respiratory system;
muscular - we move thanks to the contraction of the muscles of our body, we carry out a variety of movements: from the simplest wiggle of the little finger to high-speed running. By the way, the heartbeat also occurs due to the contraction of muscle tissue;
connective tissue makes up 80 percent of the mass of all organs and plays a protective and supporting role;
nervous - forms nerve fibers. Thanks to her, various impulses pass through the body.

Reproduction process

Throughout the life of the body, mitosis occurs - this is the name of the division process,consisting of four stages:

Prophase... The two centrioles of the cell divide and go in opposite directions. At the same time, the chromosomes form pairs, and the nuclear envelope begins to break down.
The second stage was named metaphases... Chromosomes are located between the centrioles, gradually the outer shell of the nucleus completely disappears.
Anaphase is the third stage, during which the centrioles continue to move in the opposite direction from each other, and individual chromosomes also follow the centrioles and move away from each other. The cytoplasm and the entire cell begin to shrink.
Telophase - the final stage. The cytoplasm contracts until two identical new cells appear. A new membrane is formed around the chromosomes and one pair of centrioles appears in each new cell.

Interesting! Cells in the epithelium divide faster than in bone tissue. It all depends on the density of the fabrics and other characteristics. The average life span of the main structural units is 10 days.

Cell structure. Cell structure and function. Cell life.

Conclusion

You have learned what is the structure of the cell - the most important component of the body. Billions of cells make up an amazingly wisely organized system that ensures the efficiency and functioning of all representatives of the animal and plant world.

Cell …………………………………………………………… 1

Cell structure …………………………………………………… 2

Cytology ………………………………………………………… ..3

Microscope and cell …………………………………………… ..4

Diagram of the structure of the cell .............................................................. 6

Cell division …………………………………………………… 10

Scheme of mitotic cell division ………………………… ... 12

Cell

A cell is an elementary part of an organism, capable of independent existence, self-reproduction and development. The cell is the basis of the structure and vital activity of all living organisms and plants. Cells can exist both as independent organisms and as part of multicellular organisms (tissue cells). The term "Cell" was proposed by the English microscopist R. Hooke (1665). The cell is the subject of study of a special section of biology - cytology. A more systematic study of cells began in the nineteenth century. One of the largest scientific theories of that time was the Cell theory, which asserted the unity of the structure of all living nature. The study of all life at the cellular level is at the heart of modern biological research.

In the structure and functions of each cell, signs are found common to all cells, which reflects the unity of their origin from primary organic substances. The particular features of various cells are the result of their specialization in the process of evolution. Thus, all cells equally regulate metabolism, double and use their hereditary material, receive and utilize energy. At the same time, different unicellular organisms (amoeba, slippers, ciliates, etc.) differ quite a lot in size, shape, and behavior. The cells of multicellular organisms differ no less sharply. So, a person has lymphoid cells - small (about 10 microns in diameter) rounded cells involved in immunological reactions, and nerve cells, some of which have processes more than a meter long; these cells carry out the main regulatory functions in the body.

The first cytological research method was microscopy of living cells. Modern variants of intravital light microscopy - phase contrast, luminescent, interference, etc. - allow you to study the shape of cells and the general structure of some of its structures, the movement of cells and their division. Details of the cell structure are revealed only after special contrasting, which is achieved by staining the killed cell. A new stage in the study of cell structure is electron microscopy, which has a significantly higher resolution of the cell structure in comparison with light microscopy. The chemical composition of cells is studied by cyto - and histochemical methods, which make it possible to find out the localization and concentration of a substance in cellular structures, the intensity of synthesis of substances and their movement in cells. Cytophysiological methods allow the study of cell functions.

Cell structure

The cells of all organisms have a single structural plan, in which the commonality of all vital processes is clearly manifested. Each cell includes two inextricably linked parts: the cytoplasm and the nucleus. Both the cytoplasm and the nucleus are characterized by the complexity and strict ordering of the structure and, in turn, they include many different structural units that perform very specific functions.

Shell. It directly interacts with the external environment and interacts with neighboring cells (in multicellular organisms).

The shell is the custom of the cell. She vigilantly monitors that substances unnecessary at the moment do not penetrate into the cell; on the contrary, the substances that the cell needs can count on its maximum assistance.

The shell of the core is double; consists of inner and outer nuclear membranes. The perinuclear space is located between these membranes. The outer nuclear membrane is usually associated with the channels of the endoplasmic reticulum.

The core shell contains numerous pores. They are formed by closing the outer and inner membranes and have different diameters. In some nuclei, for example the nuclei of oocytes, there are a lot of pores and they are located at regular intervals on the surface of the nucleus. The number of pores in the nuclear envelope varies in different types of cells. The pores are equally spaced from each other. Since the pore diameter can vary, and in some cases its walls have a rather complex structure, it seems that the pores are shrinking, or closed, or, conversely, expanding. Thanks to the pores, the karyoplasm comes into direct contact with the cytoplasm. Quite large molecules of nucleosides, nucleotides, amino acids and proteins easily pass through the pores, and thus an active exchange between the cytoplasm and the nucleus takes place.

Cytology

The science that studies the structure and function of cells is called cytology.

Over the past decade, it has achieved great success, which is largely associated with the development of new methods for studying the cell.

The main "tool" of cytology is a microscope, which allows you to study the structure of a cell with a magnification of 2400-2500 times. The cells are examined in a live state, as well as after special treatment. The latter boils down to two main stages.

First, the cells are fixed, that is, they are killed with fast-acting substances that are poisonous for the cells and do not destroy their structures. The second stage is coloring the preparation. It is based on the fact that different parts of the cell perceive some dyes with varying degrees of intensity. Thanks to this, it is possible to clearly identify the various structural components of the cell, which are not visible without color due to a similar refractive index. The method of making slices is very often used. For this, tissues or individual cells after special processing are enclosed in a solid medium (paraffin, celloidin), after which, using a special device - a microtome equipped with a sharp razor, they are laid out into thin sections with a thickness of 3 microns (micron \u003d 0.001 mm).

1. Not all organisms have a cellular structure.

Cellular organization is the result of a long evolution, which was preceded by non-cellular (precellular) life forms. Before the study, fixed and colored preparations are enclosed in a medium with a high refractive index (glycerin, Canadian balsam, etc.). Thanks to this, they become transparent, which facilitates the study of the drug.

In modern cytology, a number of new methods and techniques have been developed, the application of which has greatly deepened the knowledge of the structure and physiology of the cell.

The use of biochemical and cytochemical methods is very important for the study of cells. Currently, we can not only study the structure of the cell, but also determine its chemical composition and changes in it during the life of the cell. Many of these methods are based on the use of color reactions to distinguish between specific chemicals or groups of substances. The study of the distribution of substances of different chemical composition in the cell by color reactions is a cytochemical method. It is of great importance for the study of metabolism and other aspects of cell physiology.

Microscope and cell

Ultraviolet microscopy is widely used in modern cytology. Ultraviolet rays are invisible to the human eye, but are perceived by a photographic plate. Certain organic substances (nucleic acids), which play a particularly important role in the life of the cell, selectively absorb ultraviolet rays. Therefore, the images taken in ultraviolet rays can be used to judge the distribution of nucleic acids in the cell.

A number of subtle methods have been developed to study the penetration of various substances into the cell from the environment.

For this, in particular, vivo (vital) dyes are used. These are dyes (for example, neutral red) that penetrate the cell without killing it. Observing a living vitally stained cell, one can judge the ways of penetration and accumulation of substances in the cell.

Electron microscopy played a particularly important role in the development of cytology, as well as in the study of the fine structure of protozoa.

The electron microscope is based on a different principle than the light optical microscope. The object is studied in a beam of rapidly flying electrons. The wavelength of electron beams is many thousands of times shorter than the wavelength of light beams. This makes it possible to obtain a significantly higher resolution, i.e., a much higher magnification than in a light microscope. An electron beam passes through the object under study and then falls on a fluorescent screen, on which the image of the object is projected. For an object to be permeable to an electron beam, it must be very thin. Ordinary microtome sections with a thickness of 3-5 microns are completely unsuitable for this. They will completely absorb the electron beam. Special devices were created - ultramicrotomes, which make it possible to obtain slices of negligible thickness, of the order of 100-300 angstroms (angstroms is a unit of length equal to one ten-thousandth of a micron). The differences in the absorption of electrons by different parts of the cell are so small that they cannot be detected without special processing on the screen of an electron microscope. Therefore, the objects under study are pretreated with substances that are impenetrable or difficult to penetrate for electrons. This substance is osmium tetroxide (Os04). It is absorbed to varying degrees by different parts of the cell, which, due to this, retain electrons in different ways.

Using an electron microscope, magnifications of the order of 100,000 can be obtained.

Electron microscopy opens up new perspectives in the study of cell organization.

Cell structure diagram

In fig. 15 and fig. 16 compares the diagram of the structure of the cell, as it was presented in the twenties of this century and as it is presented at the present time.

Outside, the cell is delimited from the environment by a thin cell membrane, which plays an important role in regulating the flow of substances into the cytoplasm. The main substance of the cytoplasm has a complex chemical composition.

It is based on proteins that are in the state of a colloidal solution. Proteins are complex organic substances with large molecules (their molecular weight is very high, measured in tens of thousands in relation to a hydrogen atom) and high chemical mobility. In addition to proteins, many other organic compounds (carbohydrates, fats) are present in the cytoplasm, among which complex organic substances - nucleic acids - play a particularly important role in the life of the cell. Of the inorganic constituents of the cytoplasm, one should first of all name water, which, by weight, makes up significantly more than half of all substances that make up the cell. Water is important as a solvent, since metabolic reactions take place in a liquid medium. In addition, the cell contains salt ions (Ca2 +, K +, Na +, Fe2 +, Fe3 +, etc.).

Organelles are located in the main substance of the cytoplasm - constantly present structures that perform certain functions in the life of the cell. Among them, mitochondria play an important role in metabolism. In a light microscope, they are visible in the form of small rods, threads, and sometimes granules.

The electron microscope has shown that the structure of mitochondria is very complex. Each mitochondrion has an envelope consisting of three layers and an internal cavity.

Numerous partitions protrude from the shell into this cavity filled with liquid contents, which do not reach the opposite wall, called to the rust and. Cytophysiological studies have shown that mitochondria are organelles with which the respiratory processes of the cell (oxidative) are associated. Respiratory enzymes (organic catalysts) are localized in the inner cavity, on the membrane and cristae, which provide complex chemical transformations, from which the respiration process is composed.

In the cytoplasm, in addition to mitochondria, there is a complex system of membranes that together form the endoplasmic reticulum (Fig. 16).

As shown by electron microscopic studies, the membranes of the endoplasmic reticulum are double. On the side facing the main substance of the cytoplasm, on each membrane there are numerous granules (called "Pallas corpuscles" after the name of the scientist who discovered them). These granules contain nucleic acids (namely ribonucleic acid), which is why they are also called ribosomes. On the endoplasmic reticulum, with the participation of ribosomes, one of the main processes of cell life is carried out - protein synthesis.

Part of the cytoplasmic membranes is devoid of ribosomes and forms a special system called the Golgi apparatus.

This formation has been found in cells for a long time, because it can be detected by special methods when examined in a light microscope. However, the fine structure of the Golgi apparatus became known only as a result of electron microscopic studies. The functional significance of this organoid comes down to the fact that various substances synthesized in the cell are concentrated in the area of \u200b\u200bthe apparatus, for example, secretion grains in glandular cells, etc. The membranes of the Golgi apparatus are in connection with the endoplasmic reticulum. It is possible that a number of synthetic processes occur on the membranes of the Golgi apparatus.

The endoplasmic reticulum is connected to the outer membrane of the nucleus. This connection apparently plays an essential role in the interaction between the nucleus and the cytoplasm. The endoplasmic reticulum also has a connection with the outer membrane of the cell and in places directly passes into it.

Another type of organelle, lysosomes, was discovered in cells using an electron microscope (Fig. 16).

They resemble mitochondria in size and shape, but are easily distinguished from them by the absence of the fine internal structure so characteristic and typical of mitochondria. According to the majority of modern cytologists, lysosomes contain digesting enzymes associated with the breakdown of large molecules of organic substances entering the cell. These are like reservoirs of enzymes gradually used in the process of cell life.

In the cytoplasm of animal cells, the centrosome is usually located in the vicinity of the nucleus. This organoid has a permanent structure. It is composed of nine ultramicroscopic rod-shaped formations, enclosed in a specially differentiated dense cytoplasm. The centrosome is an organoid associated with cell division.

Figure: 16. Scheme of the structure of the cell, according to modern data, taking into account electron microscopic studies:

1 - cytoplasm; 2 - Golgi apparatus, s - centrosome; 4 - mitochondria; 5 - endoplasmic reticulum; 6 - core; 7 - nucleolus; 8 - lysosomes.

In addition to the listed cytoplasmic organelles of the cell, it may contain various special structures and inclusions associated with metabolism and the performance of various special functions inherent in this cell. Animal cells usually contain glycogen, or animal starch. It is a reserve substance consumed in the metabolic process as the main material for oxidative processes. Fat inclusions are often present in the form of small droplets.

In specialized cells, such as muscle cells, there are special contractile fibers associated with the contractile function of these cells. A number of special organelles and inclusions are found in plant cells. In the green parts of plants, chloroplasts are always present - protein bodies containing the green pigment chlorophyll, with the participation of which photosynthesis is carried out - the process of air nutrition of the plant. Starch grains, which are absent in animals, are usually found here as a reserve substance. In contrast to animals, plant cells have, in addition to the outer membrane, strong walls of cellulose and, which determines the special strength of plant tissues.

Cell division

The ability of cells to self-replicate is based on the unique property of DNA to self-copy and the strictly equivalent division of reproduced chromosomes in the process of mitosis. As a result of division, two cells are formed, identical to the original one in genetic properties and with a renewed composition of the nucleus and cytoplasm. The processes of self-reproduction of chromosomes, their division, the formation of two nuclei and division of the cytoplasm are separated in time, making up the aggregate mitotic cycle of the cell. If, after division, the cell begins to prepare for the next division, the mitotic cycle coincides with the cell's life cycle. However, in many cases, after division (and sometimes before it), the cells leave the mitotic cycle, differentiate and perform this or that special function in the body. The composition of such cells can be renewed due to divisions of poorly differentiated cells. In some tissues, differentiated cells are able to re-enter the mitotic cycle. In the nervous tissue, differentiated cells do not divide; many of them live as long as the organism as a whole, that is, in humans - several decades. At the same time, the nuclei of nerve cells do not lose the ability to divide: being transplanted into the cytoplasm of cancer cells, the nuclei of neurons synthesize DNA and divide. Experiments with hybrid cells show the influence of the cytoplasm on the manifestation of nuclear functions. Inadequate preparation for division prevents mitosis or distorts its course. So, in some cases, there is no division of the cytoplasm and a binucleated cell is formed. Multiple division of nuclei in a non-dividing cell leads to the appearance of multinucleated cells or complex supracellular structures (symplasts), for example, in striated muscles. Sometimes the reproduction of a cell is limited to the reproduction of chromosomes, and a polyploid cell is formed, which has a doubled (compared to the original cell) set of chromosomes. Polyploidization leads to increased synthetic activity, an increase in the size and mass of the cell.

One of the main biological processes ensuring the continuity of life forms and underlying all forms of reproduction is the process of cell division. This process, known as karyokinesis, or mitosis, with surprising constancy, with only some variations in details, is carried out in the cells of all plants and animals, including protozoa. During mitosis, a uniform distribution of chromosomes occurs, undergoing duplication between daughter cells. From any part of each chromosome, daughter cells receive half. Without going into a detailed description of mitosis, we will only note its main points (Fig.).

In the first stage of mitosis, called prophase, chromosomes in the form of filaments become clearly visible in the nucleus.

Figure: Scheme of mitotic cell division:

1 - non-fissile core;

2-6 - successive stages of changes in the nucleus in prophase;

7-9 - metaphase;

10 - anaphase;

11-13 - telophase. different lengths.

In the nondividing nucleus, as we have seen, the chromosomes look like thin, irregularly placed filaments intertwined with each other. In prophase, they are shortened and thickened. At the same time, each chromosome turns out to be double. A slit runs along its length, dividing the chromosome into two adjacent halves that are completely similar to each other.

At the next stage of mitosis - metaphase - the nuclear membrane is destroyed, the nucleoli dissolve and the chromosomes are lying in the cytoplasm. All chromosomes are arranged in one row, forming the so-called equatorial plate. The centrosome undergoes significant changes. It is divided into two parts, which diverge, and threads are formed between them, forming an akhromatin spindle. The equatorial plate of chromosomes is located at the equator of this spindle.

At the stage of anaphase, the process of divergence to opposite poles of daughter chromosomes occurs, formed, as we have seen, as a result of longitudinal cleavage of the maternal chromosomes. Chromosomes diverging in anaphase slide along the filaments of the achromatin spindle and eventually assemble in two groups in the region of the centrosome.

During the last stage of mitosis - telophase - the structure of the non-dividing nucleus is restored. A nuclear envelope is formed around each group of chromosomes. Chromosomes stretch and thin out into long, randomly spaced, thin threads. Nuclear juice is released, in which the nucleolus appears.

Simultaneously with the stages of anaphase and telophase, the cytoplasm of the cell is divided into two halves, which is usually carried out by a simple constriction.

As can be seen from our brief description, the process of mitosis is reduced primarily to the correct distribution of chromosomes between daughter nuclei. Chromosomes are made up of bundles of thread-like DNA molecules located along the longitudinal axis of the chromosome. The apparent onset of mitosis is preceded, as is now established by precise quantitative measurements, by DNA duplication, the molecular mechanism of which we have already discussed above.

Thus, mitosis and splitting of chromosomes during it is only a visible expression of the processes of duplication (autoreproduction) of DNA molecules, carried out at the molecular level. DNA determines protein synthesis through RNA. The qualitative features of proteins are "encoded" in the DNA structure. Therefore, it is obvious that the exact division of chromosomes in mitosis, based on the replication (autoreproduction) of DNA molecules, underlies the "hereditary information" in a number of successive generations of cells and organisms.

The number of chromosomes, as well as their shape, size, etc., is a characteristic feature of each type of organism. A human, for example, has 46 chromosomes, a perch has 28, a soft wheat has 42, etc.

Cell biology (cell biology, cytology) - the science of the cell.

Cellular biology is a branch of biology, the subject of which is a cell, an elementary unit of living. The cell is considered as a system that includes individual cellular structures, their participation in general cellular physiological processes, and ways of regulating these processes. Reproduction of cells and their components, adaptation of cells to environmental conditions, reactions to the action of various factors, pathological changes in cells are considered. and the mechanisms of their death.

Cytology and Cell Biology

The term "Cell Biology" or "Cell Biology" in the second half of the 20th century supplanted the original original term "Cytology", which defined the science of the cell. Cytology belongs to a number of "happy" biological disciplines, such as biochemistry, biophysics, and genetics, the development of which over the past 60 years has been particularly rapid ("biological revolution") and has made dramatic changes in biology in understanding the organization and essence of life phenomena. Classical cytology, which in the beginning was mainly. a descriptive morphological science, having absorbed the ideas, facts and methods of biochemistry, biophysics and molecular biology, has become a general biological discipline that studies not only the structure, morphology, but also the functional and molecular aspects of the behavior of cells as elementary units of living nature.

Although the first descriptions and concepts of the cell appeared more than 300 years ago, the detailed study of cells was associated with the development of microscopy in the 19th century. At this time, the main descriptions of the intracellular organization were made and the so-called. cell theory (T. Schwann. R. Virchow), the main postulates of which are: a cell is an elementary unit of living; there is no life outside the cell (according to R. Virchow, “life is the activity of the cell, the features of the first are features and the last”); cells are similar (homologous) in their structure and in their basic properties; cells increase in number, multiply only by dividing the original cells. The cell theory not only had a significant impact on the development of such general biological disciplines as histology, embryology and physiology, but also made a real revolution in medicine, showing that any diseases of the body are based on cellular pathology, i.e. changes in the functioning of individual groups of cells in the composition of organs and tissues.

An important role in the formation and development of domestic biology and, in the future, cell biology was played by the scientific schools of such researchers as I.I. Mechnikov, N.K. Koltsov, D.N. Nasonov and others.

By the end of the 19th century, many intracellular components were described (nucleus, chromosomes, mitochondria, etc.), mitosis was characterized as the only way of cell reproduction, and the chromosomal theory of heredity (cytogenetics) was created. At the same time and at the beginning of the 20th century, the interests of cytology were aimed at elucidating the functional significance of intracellular components (cytophysiology). The development of such areas as cytochemistry, cell cultivation associated with the introduction of new methodological techniques (fluorescence microscopy, quantitative cytochemistry, autoradiography, differential centrifugation, etc.) helped to solve these problems.

A qualitative breakthrough in the analysis of cellular components and their functional significance was the introduction of electron microscopy in the 50s of the 20th century, which made it possible to study cells at a submicroscopic level. The combination of electron microscopic and molecular biological methods made it possible to closely link the study of the morphology of cell components with the identification of their biochemical characteristics and establish their functional significance. It was in the middle of the 20th century that the term "cell biology" began to be used as a definition of science, which studies not only the structure of cells, but also the functional and biochemical characteristics of their structures and individual stages of cell life in general. At the same time, the cell cycle was discovered (the molecular sequence of events during cell reproduction), its regulation at the molecular level, and the functional and biochemical characteristics of many old and newly discovered intracellular structures were given.

The doctrine of the cell

At present, from the standpoint of modern molecular biology, the following definition can be made of what a cell is: a cell is an ordered system of biopolymers (proteins, nucleic acids, lipids) and their macromolecular complexes, which participate in a single set of metabolic (metabolic) and energetic ones, limited by an active lipoprotein membrane. processes that maintain and reproduce the entire system as a whole.

Intracellular structural elements are functional subsystems, or second-order systems. Thus, the cell nucleus is a system for storing, reproducing and realizing genetic information contained in the DNA of chromosomes; hyaloplasm (main plasma) - a system of basic intermediate metabolism and synthesis of monomers, as well as protein synthesis on ribosomes; cytoskeleton - the musculoskeletal system of the cell; vacuolar system - a system for the synthesis, modification and transport of some protein polymers and the formation of many cell lipoprotein membranes; mitochondria - organelles of energy supply for all cell functions due to the synthesis of ATP; plant cell plastids - a system of ATP photosynthesis and carbohydrate synthesis; the plasma membrane is the barrier-receptor-transport system of the cell.

It is important to emphasize that all these subsystems of the cell form a kind of conjugate unity, which is mutually dependent. So, a violation of the function of the nucleus immediately affects the synthesis of proteins, a violation of the structure and function of mitochondria stops all synthetic and metabolic processes, a violation of the elements of the cytoskeleton stops intracellular transport, etc.

Modern biochemistry and molecular biology, which study the chemical processes that underlie the vital activity of cells, cannot do without information about the structures on which these processes occur; just as in cell biology, in the study of structures and their functional significance, it is impossible to do without knowledge of the molecular processes occurring on these structures. Therefore, the term "molecular biology of the cell" is increasingly used in the titles of various manuals and textbooks.

The study of cell biology is of great practical importance: it is the study of the physiology of organisms, the use of cells in biotechnological developments, the use of data from cell biology in practical medicine. So, for example, information from the field of cell biology is necessary in the study of malignant cell growth, for cytodiagnostics of a disease, for the use of stem cells, etc. Moreover, any human disease cannot be understood without drawing on data from cell biology.

Outstanding Russian scientists-cytologists

II Mechnikov (1845-1916) - a famous Russian biologist and pathologist, one of the founders of experimental cytology and immunology, the founder of a scientific school, an honorary member of the St. Petersburg Academy of Sciences, one of the founders of the Pasteur Institute in Paris. In 1883 II Mechnikov discovered the phenomenon of phagocytosis, put forward the phagocytic theory of immunity (1901); for his work on the study of immunity together with P. Ehrlich was awarded the Nobel Prize in 1908.

The scientific school of N.K. Koltsov (1872-1940) had a huge influence on the development of biology, genetics and cytology in our country. He was a researcher whose ideas were decades ahead of many discoveries that became the foundations of modern concepts in genetics and cell biology. NK Koltsov in 1903 discovered an internal fibrillar system, which he defined as a skeletal cytoplasmic structure that determines the shape and movement of cells. At present, this system is called the cytoskeleton; it contains protein polymers, from which microtubules and filamentous structures (microfilaments, intermediate filaments) are formed. Another major achievement of N.K. Koltsov was the prediction of the matrix principle of doubling hereditary structures. According to him, small molecules of the nucleus are assembled on an already existing template, and then "merge" into a polymer molecule, into a copy of the template. At that time (1927) it was not yet known about DNA macromolecules, but the idea that a permanent conservative hereditary matrix is \u200b\u200bnot destroyed and does not arise anew, but is passed from parents to descendants, was a great prediction. It can be considered that this statement of N.K. Koltsov was the beginning of the development of molecular biology. Long-term research on the shape and behavior of cells (cytoskeleton) and the matrix hypothesis are the greatest merit of N.K. Koltsov as a "prophet in his homeland" in the development of biology. The great merit of N.K. Koltsov, in addition, is that he brought up a whole galaxy of his disciples-followers: geneticists, physiologists, embryologists and cytologists. These include V.V. Sakharov, B.L. Astaurov, S.S. Chetverikov, D.P. , A.S. Serebrovsky, G.I. Roskin and others. Now it is customary to talk about the biological Russian school of N.K. Koltsov. The Institute of Developmental Biology of the Russian Academy of Sciences now bears his name.

An important role in the creation of Russian cytology was played by D.N. Nasonov (1895-1957). Dmitry Nikolaevich's works devoted to the study of the Golgi apparatus were highly appreciated by specialists and became classical. When studying the work of the Golgi apparatus D.N. Nasonov put forward a hypothesis about the leading role of this organoid in the cellular secretory process. Much later, with the help of electron microscopic autoradiography, this hypothesis was fully confirmed (Leblond, 1966) and became the axiom of the functional significance of this structure. In 1956, on the initiative of Dmitry Nikolaevich, the Institute of Cytology of the USSR Academy of Sciences was organized.

One of the students of N.K. Koltsov was G.I. Roskin (1882-1964), who worked with him since 1912. He investigated skeletal and contractile structures in various cells, ranging from unicellular to smooth and striated muscles of multicellular organisms. He concluded that contractile and supporting elements form very complex systems that provide motor and support functions - these systems were called statokinetic. This cycle of works is a continuation of the cytoskeleton studies started by N.K. Koltsov.

From 1930 to 1964 GI Roskin was in charge of the Department of Histology at Moscow State University. Continuing to study the contractile elements of the cell, G.I. Roskin paid great attention to the study of the cytology of cancer cells, which led to the discovery of the anti-cancer drug crucin, which was used for some time in the clinic. Special attention of G.I. Roskin devoted himself to the introduction of cytochemistry methods into histology and cytology, which make it possible to localize certain polymers or individual amino acids in cells. At this time, the Department of Histology became a promoter of cytochemical methods, which were widely used not only in biological research, but also in medicine. Later V.Ya. Brodsky, a student of G.I. Roskin, began to develop quantitative histochemical studies using special cytophotometric equipment. This led to the emergence of new biochemical and biophysical methods that are widely used in cell biology.

A great contribution to the study of the structure and behavior of tumor cells was made by the works of Yu.M. Vasiliev (born 1928) and his students. For many years his school has been studying the mechanisms of movement of normal and tumor cells. He was the first to reveal the role of the microtubule system and other elements of the cytoskeleton in determining the direction of migration of both normal and tumor cells. He directs the laboratory of mechanisms of carcinogenesis of the Cancer Research Center of the Russian Academy of Medical Sciences.

Yu.S. Chentsov (born 1930) headed the Department of Cell Biology and Histology from 1970 to 2010. He is one of the founders of the Moscow School of Electron Microscopists. He and his students were the first to create a three-dimensional reconstruction of the centriole and describe its behavior in the cell cycle. Yu.S. Chentsov is one of the authors of the discovery of the nuclear protein backbone (matrix), he showed that the nuclear matrix is \u200b\u200ban integral part of interphase and mitotic chromosomes. Yu.S. Chentsov played an important role in the study of the ultrastructure of the cell nucleus and the mitotic chromosome. In works on the study of mitochondria in muscle tissue, Y.S. Chentsov became one of the authors of the discovery of the mitochondrial reticulum and a special structure - intermitochondrial contacts. (Daniel Mazia, 1912-1996), an American cytologist who played an important role in the study of the processes of cell division and reproduction, in the study of the structure of the mitotic spindle and the reproduction of centrosomes. He considered the cell to be a supramolecular system consisting of many interconnected molecular systems.

Keith Porter (Keith Robert Porter, 1912-1997) - Canadian biologist, one of the founders of the electron microscopic approach in biology. He developed methods for the production of ultrathin sections, methods for using coated grids in electron microscopy, and also proposed using osmium tetroxide for working with electron microscopic preparations. K. Porter discovered cytoskeletal microtubules and endoplasmic reticulum, autolysosomes and bordered vacuoles. Thanks to him, the first leading journal in cell biology was founded, which is now called the Journal of Cell Biology.

George Palade (George Emil Palade, 1912-2008) is an American biologist of Romanian origin. Discovered on the surface of endoplasmic reticulum cisterns ribonucleic particles called Palade granules. Subsequently, it was found that Palade granules are ribosomes associated with the endoplasmic reticulum. Palade worked extensively on the study of the vacuolar system and vesicular transport in the cell. In 1974 he was awarded the Nobel Prize.

Christian Rene de Duve (1917-2002) is a Belgian cytologist and biochemist who discovered the existence of digestive organelles in the cell - lysosomes. Nobel Prize Laureate (1974).

Albert Claude (1899-1983) is a Belgian biochemist, thanks to whom cytology from a descriptive science to a functional science. He showed a direct connection between intracellular structures and biochemical processes occurring in the cell, participated in the introduction of biochemical and physical methods into cytology. A. Claude wrote that a cell is “an independent and self-supporting unit of living matter, capable of accumulating, transforming and using energy”. Nobel Prize Laureate (1974).

A branch of biology that studies the structure of the cell. All about the cell. The cage is

Prokaryotic cell

Eukaryotic cell

The structure of the eukaryotic cell

Surface complex of an animal cell

Cytoplasm structure

Endoplasmic reticulum

Golgi apparatus

Core

Cytoskeleton

Centrioli

Mitochondria

Comparison of pro- and eukaryotic cells

Anaplasia

Cell discovery history

see also

Links

See what "Cell (biology)" is in other dictionaries:

Structural features

Core

Cell membrane

Chloroplasts

Fabrics

Reproduction process

Conclusion

Cytology and Cell Biology

The doctrine of the cell

Outstanding Russian scientists-cytologists

Recommended reading