The relationship of the body with the environment. Biological evolution Implementation of the interaction of the cell with the environment
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: cellulose membrane, membrane, cytoplasm with organelles, nucleus, vacuoles with cell juice.The presence of plastids is the main feature of a plant cell.
Cell wall functions- determines the shape of the cell, protects against environmental factors.
Plasma membrane- a thin film, consisting of interacting molecules of lipids and proteins, delimits the internal contents from the external environment, ensures the transport of water, mineral and organic matter by osmosis and active transfer, and also removes waste products.
Cytoplasm- the internal semi-liquid environment of the cell, in which the nucleus and organelles are located, provides connections between them, participates in the main life processes.
Endoplasmic reticulum- a network of branching channels in the cytoplasm. It participates in the synthesis of proteins, lipids and carbohydrates, in the transport of substances. Ribosomes - bodies located on the EPS or in the cytoplasm, consist of RNA and protein, are involved in protein synthesis. EPS and ribosomes are a single apparatus for the synthesis and transport of proteins.
Mitochondria- organelles separated from the cytoplasm by two membranes. In them, organic substances are oxidized and ATP molecules are synthesized with the participation of enzymes. An increase in the surface of the inner membrane, on which enzymes are located due to cristae. ATP is an energy-rich organic substance.
Plastids(chloroplasts, leukoplasts, chromoplasts), their content in the cell is the main feature of the plant organism. Chloroplasts are plastids containing the green pigment chlorophyll, which absorbs light energy and uses it to synthesize organic substances from carbon dioxide and water. The separation of chloroplasts from the cytoplasm by two membranes, numerous outgrowths - granules on the inner membrane, in which chlorophyll molecules and enzymes are located.
Golgi complex- a system of cavities delimited from the cytoplasm by a membrane. The accumulation of proteins, fats and carbohydrates in them. Implementation of the synthesis of fats and carbohydrates on the membranes.
Lysosomes- bodies separated from the cytoplasm by one membrane. The enzymes they contain accelerate the breakdown reaction of complex molecules to simple ones: proteins to amino acids, complex carbohydrates to simple ones, lipids to glycerol and fatty acids, and also destroy dead parts of cells, whole cells.
Vacuoles- cavities in the cytoplasm, filled with cell sap, a place of accumulation of reserve nutrients, harmful substances; they regulate the water content in the cell.
Core- the main part of the cell, covered on the outside by two membranes, permeated with pores by the nuclear envelope. Substances enter the core and are removed from it through the pores. Chromosomes are carriers of hereditary information about the characteristics of an organism, the main structures of the nucleus, each of which consists of one DNA molecule in conjunction with proteins. The nucleus is the place of synthesis of DNA, i-RNA, r-RNA.
Availability outer membrane, cytoplasm with organelles, nuclei with chromosomes.
Outer, or plasma, membrane- delimits the contents of the cell from the environment (other cells, intercellular substance), consists of lipid and protein molecules, provides communication between cells, the transport of substances into the cell (pinocytosis, phagocytosis) and out of the cell.
Cytoplasm- the internal semi-liquid environment of the cell, which provides a connection between the nucleus located in it and the organelles. The main life processes take place in the cytoplasm.
Cell organelles:
1) endoplasmic reticulum (EPS)- the system of branching tubules, is involved in the synthesis of proteins, lipids and carbohydrates, in the transport of substances in the cell;
2) ribosomes- bodies containing rRNA are located on the EPS and in the cytoplasm, are involved in protein synthesis. EPS and ribosomes are a single apparatus for protein synthesis and transport;
3) mitochondria- "power stations" of the cell, delimited from the cytoplasm by two membranes. The inner one forms cristae (folds) that increase its surface. Enzymes on cristae accelerate the oxidation reactions of organic substances and the synthesis of energy-rich ATP molecules;
4) Golgi complex- a group of cavities delimited by a membrane from the cytoplasm, filled with proteins, fats and carbohydrates, which are either used in vital processes or removed from the cell. The synthesis of fats and carbohydrates is carried out on the membranes of the complex;
5) lysosomes- bodies filled with enzymes accelerate the reactions of protein splitting to amino acids, lipids to glycerol and fatty acids, polysaccharides to monosaccharides. In lysosomes, dead cell parts, whole cells and cells are destroyed.
Cellular inclusions- accumulations of reserve nutrients: proteins, fats and carbohydrates.
Core is the most important part of the cell. It is covered with a two-membrane membrane with pores through which some substances penetrate into the nucleus, while others enter the cytoplasm. Chromosomes are the main structures of the nucleus, carriers of hereditary information about the characteristics of the organism. It is transmitted in the process of division of the mother cell to daughter cells, and with reproductive cells - to daughter organisms. The nucleus is the place of synthesis of DNA, mRNA, rRNA.
Exercise:
Explain why organelles are called specialized cell structures?
Answer: organelles are called specialized cell structures, since they perform strictly defined functions, hereditary information is stored in the nucleus, ATP is synthesized in mitochondria, photosynthesis occurs in chloroplasts, etc.
If you have questions about cytology, then you can ask for help from
Metabolism that enters the cell or is released by it outside, as well as the exchange of various signals with the micro- and macroenvironment, occurs through the outer membrane of the cell. As you know, the cell membrane is a lipid bilayer in which various protein molecules are embedded that act as specialized receptors, ion channels, devices that actively transfer or remove various chemicals, intercellular contacts, etc. In healthy eukaryotic cells, phospholipids are asymmetrically distributed in the membrane: the outer surface consists of sphingomyelin and phosphatidylcholine, the inner surface consists of phosphatidylserine and phosphatidylethanolamine. Maintaining this asymmetry requires an expenditure of energy. Therefore, in case of cell damage, infection, energy starvation, the outer surface of the membrane is enriched with phospholipids unusual for it, which becomes a signal for other cells and enzymes to damage the cell with an appropriate response to this. The most important role is played by the soluble form of phospholipase A2, which cleaves arachidonic acid and creates lysoforms from the above phospholipids. Arachidonic acid is a limiting link for the creation of inflammatory mediators such as eicosanoids, and protective molecules - pentraxins (C-reactive protein (CRP), precursors of amyloid proteins) - are attached to lysoforms in the membrane, followed by activation of the complement system by the classic way and cell destruction.
The structure of the membrane helps to preserve the characteristics of the internal environment of the cell, its differences from the external environment. This is provided by the selective permeability of the cell membrane, the existence of mechanisms in it active transport... Their violation as a result of direct damage, for example, tetrodotoxin, ouabain, tetraethylammonium, or in the case of insufficient energy supply of the corresponding "pumps" leads to a violation of the electrolyte composition of the cell, a change in its metabolism, a violation of specific functions - contraction, conduction of an excitation pulse, etc. Disruption of cellular ion channels (calcium, sodium, potassium and chloride) in humans can also be genetically caused by mutations in genes responsible for the structure of these channels. The so-called canalopathies are the cause of hereditary diseases of the nervous, muscular, and digestive systems. Excessive intake of water inside the cell can lead to its rupture - cytolysis - due to membrane perforation during complement activation or attack of cytotoxic lymphocytes and natural killer cells.
Many receptors are built into the cell membrane - structures that, when combined with the corresponding specific signaling molecules (ligands), transmit a signal to the inside of the cell. This occurs through various regulatory cascades consisting of enzymatically active molecules that are sequentially activated and ultimately contribute to the implementation of various cellular programs, such as growth and proliferation, differentiation, motility, aging, and cell death. Regulatory cascades are quite numerous, but their number has not yet been fully determined. The system of receptors and associated regulatory cascades also exist inside the cell; they create a specific regulatory network with points of concentration, distribution and choice of further signal pathways, depending on the functional state of the cell, the stage of its development, and the simultaneous action of signals from other receptors. The result of this can be inhibition or amplification of the signal, its direction along a different regulatory path. Both the receptor apparatus and the signal transmission pathways through regulatory cascades, for example, to the nucleus, can be disrupted as a result of a genetic defect that occurs as a congenital defect at the level of the organism or as a result of somatic mutation in a certain type of cells. These mechanisms can be damaged by infectious agents, toxins, and also change during the aging process. The final stage of this can be a violation of the functions of the cell, the processes of its proliferation and differentiation.
On the surface of cells are also molecules that play an important role in the processes of intercellular interaction. These may include proteins of cell adhesion, antigens of tissue compatibility, tissue-specific, differentiating antigens, etc. Changes in the composition of these molecules cause disruption of intercellular interactions and can cause the activation of the appropriate mechanisms for the elimination of such cells, because they pose a certain danger to the integrity of the organism as reservoir of infection, especially viral, or as potential initiators of tumor growth.
Violation of the energy supply of the cell
The source of energy in the cell is food, after the breakdown of which to the final substances, energy is released. The main place for the formation of energy is mitochondria, in which substances are oxidized with the help of enzymes of the respiratory chain. Oxidation is the main supplier of energy, since as a result of glycolysis, no more than 5% of energy is released from the same amount of oxidation substrates (glucose), compared to oxidation. About 60% of the energy released during oxidation is accumulated by oxidative phosphorylation in high-energy phosphates (ATP, creatine phosphate), the rest is dissipated as heat. In the future, high-energy phosphates are used by the cell for such processes as the operation of pumps, synthesis, division, movement, secretion, etc. There are three mechanisms, the damage of which can cause a violation of the supply of energy to the cell: the first is the mechanism of enzyme synthesis energy exchange, the second - the mechanism of oxidative phosphorylation, the third - the mechanism of energy use.
Disruption of electron transport in the respiratory chain of mitochondria or uncoupling of oxidation and phosphorylation of ADP with a loss of proton potential - driving force generation of ATP, leads to a weakening of oxidative phosphorylation in such a way that most of the energy is dissipated in the form of heat and the amount of high-energy compounds decreases. The uncoupling of oxidation and phosphorylation under the influence of adrenaline is used by cells of homeothermal organisms to increase heat production while maintaining a constant body temperature during cooling or increasing it during fever. Significant changes in the structure of mitochondria and energy metabolism are observed in thyrotoxicosis. These changes are initially reversible, but after a certain trait they become irreversible: mitochondria fragment, disintegrate or swell, lose cristae, turning into vacuoles, and eventually accumulate substances such as hyaline, ferritin, calcium, lipofuscin. In patients with scurvy, mitochondria merge to form chondriospheres, possibly due to membrane damage by peroxide compounds. Significant damage to mitochondria occurs under the influence of ionizing radiation, during the transformation of a normal cell into a malignant one.
Mitochondria are a powerful depot of calcium ions, where its concentration is several orders of magnitude higher than that in the cytoplasm. When mitochondria are damaged, calcium is released into the cytoplasm, causing the activation of proteinases with damage to intracellular structures and dysfunction of the corresponding cell, for example, calcium contractures or even “calcium death” in neurons. As a result of a violation of the functional ability of mitochondria, the formation of free radical peroxide compounds increases sharply, which have a very high reactivity and therefore damage important components of the cell - nucleic acids, proteins and lipids. This phenomenon is observed under the so-called oxidative stress and can have negative consequences for the existence of the cell. Thus, damage to the outer membrane of mitochondria is accompanied by the release into the cytoplasm of substances contained in the intermembrane space, primarily cytochrome C and some other biologically active substances, which trigger chain reactions that cause programmed cell death - apoptosis. By damaging the DNA of mitochondria, free radical reactions distort the genetic information necessary for the formation of certain enzymes of the respiratory chain, which are produced in the mitochondria. This leads to an even greater disruption of oxidative processes. In general, the mitochondria's own genetic apparatus, in comparison with the genetic apparatus of the nucleus, is less protected from harmful influences that can change the genetic information encoded in it. As a result, mitochondrial dysfunction occurs throughout life, for example, during aging, during malignant transformation of the cell, as well as against the background of hereditary mitochondrial diseases associated with mutation of mitochondrial DNA in the egg. Currently, more than 50 mitochondrial mutations have been described that cause hereditary degenerative diseases of the nervous and muscular systems. They are transmitted to the child exclusively from the mother, since the mitochondria of the sperm are not part of the zygote and, accordingly, the new organism.
Violation of storage and transmission of genetic information
The cell nucleus contains most of the genetic information and thus ensures its normal functioning. With the help of selective gene expression, it coordinates the work of the cell in interphase, stores genetic information, recreates and transmits genetic material in the process of cell division. DNA replication and RNA transcription take place in the nucleus. Various pathogenic factors such as ultraviolet and ionizing radiation, free radical oxidation, chemicals, viruses can damage DNA. It is calculated that each cell of a warm-blooded animal in 1 day. loses more than 10,000 bases. To this should be added division-time copying violations. If this damage persisted, the cell would not be able to survive. Protection lies in the existence of powerful repair systems such as ultraviolet endonuclease, a reparative replication and recombination repair system that replace DNA damage. Genetic defects in reparative systems cause the development of diseases caused by increased sensitivity to factors that damage DNA. This is xeroderma pigmentosa, as well as some accelerated aging syndromes, accompanied by an increased tendency to develop malignant tumors.
The system for regulating the processes of DNA replication, transcription of informational RNA (mRNA), translation of genetic information from nucleic acids into the structure of proteins is rather complex and multilevel. In addition to regulatory cascades that trigger the action of over 3000 transcription factors that activate certain genes, there is also a multilevel regulatory system mediated by small RNA molecules (interfering RNAs; RNAi). The human genome, which consists of approximately 3 billion purine and pyrimidine bases, contains only 2% of the structural genes responsible for protein synthesis. The rest provide the synthesis of regulatory RNAs, which, simultaneously with transcription factors, activate or block the work of structural genes at the DNA level in chromosomes or affect the translation of messenger RNA (mRNA) during the formation of a polypeptide molecule in the cytoplasm. Violation of genetic information can occur both at the level of structural genes and the regulatory part of DNA with corresponding manifestations in the form of various hereditary diseases.
Recently, much attention has been attracted by changes in the genetic material that occur in the process of individual development of the organism and are associated with inhibition or activation of certain sections of DNA and chromosomes due to their methylation, acetylation and phosphorylation. These changes persist for a long time, sometimes - throughout the entire life of the organism from embryogenesis to old age, and are called epigenomic heredity.
Reproduction of cells with altered genetic information is also hindered by systems (factors) of mitotic cycle control. They interact with cyclin-dependent protein kinases and their catalytic subunits - cyclins - and block the passage of the full mitotic cycle by the cell, stopping division at the boundary between the presynthetic and synthetic phases (block G1 / S) until the completion of DNA repair, and, if it is impossible, initiate programmed death cells. These factors include the p53 gene, a mutation of which causes a loss of control over the proliferation of transformed cells; it occurs in almost 50% of human cancers. The second checkpoint for the passage of the mitotic cycle is at the G2 / M border. Here, the correct distribution of chromosomal material between daughter cells in mitosis or meiosis is controlled using a complex of mechanisms that control the cell spindle, center and centromeres (kinetochores). The inefficiency of these mechanisms leads to a violation of the distribution of chromosomes or their parts, which is manifested by the absence of any chromosome in one of the daughter cells (aneuploidy), the presence of an extra chromosome (polyploidy), the detachment of a part of the chromosome (deletion) and its transfer to another chromosome (translocation) ... Such processes are very often observed during the multiplication of malignant degenerated and transformed cells. If this occurs during meiosis with germ cells, then it leads either to the death of the fetus at an early stage of embryonic development, or to the birth of an organism with a chromosomal disease.
Uncontrolled cell proliferation during tumor growth occurs as a result of mutations in genes that control cell proliferation and are called oncogenes. Among more than 70 currently known oncogenes, most of them belong to the components of cell growth regulation, some are represented by transcription factors that regulate gene activity, as well as factors that inhibit cell division and growth. Another factor limiting the excessive expansion (spread) of proliferating cells is the shortening of the ends of chromosomes - telomeres, which are unable to replicate completely as a result of a purely steric interaction, therefore, after each cell division, telomeres are shortened by a certain part of bases. Thus, the proliferating cells of an adult organism, after a certain number of divisions (usually from 20 to 100, depending on the type of organism and its age), exhaust the telomere length and further chromosome replication stops. This phenomenon does not occur in the sperm epithelium, enterocytes and embryonic cells due to the presence of the telomerase enzyme, which restores telomere length after each division. Telomerase is blocked in most adult cells, but unfortunately it is activated in tumor cells.
The connection between the nucleus and the cytoplasm, the transport of substances in both directions is carried out through the pores in the nuclear membrane with the participation of special transport systems with energy consumption. Thus, energy and plastic substances, signaling molecules (transcription factors) are transported to the nucleus. The reverse flow carries mRNA and transport RNA (tRNA) molecules, ribosomes, necessary for protein synthesis in the cell, into the cytoplasm. The same route of transport of substances is inherent in viruses, in particular, such as HIV. They transfer their genetic material into the nucleus of the host cell with its further incorporation into the host genome and the transfer of the newly formed viral RNA into the cytoplasm for further synthesis of proteins of new viral particles.
Violation of synthesis processes
Protein synthesis processes take place in tanks endoplasmic reticulum, closely connected with pores in the nuclear membrane, through which ribosomes, tRNA and mRNA enter the endoplasmic reticulum. Here, the synthesis of polypeptide chains is carried out, which later acquire their final form in the agranular endoplasmic reticulum and the lamellar complex (Golgi complex), where they undergo post-translational modification and combination with carbohydrate and lipid molecules. Newly formed protein molecules do not remain at the site of synthesis, but with the help of a complex regulated process, which is called protein kinesis, are actively transferred to that isolated part of the cell, where they will perform their intended function. In this case, a very important stage is the structuring of the transferred molecule into an appropriate spatial configuration capable of performing its inherent function. Such structuring occurs with the help of special enzymes or on a matrix of specialized protein molecules - chaperones, which help a protein molecule, newly formed or changed due to external influence, to acquire the correct three-dimensional structure. In the case of an adverse effect on the cell, when there is a likelihood of a violation of the structure of protein molecules (for example, with an increase in body temperature, an infectious process, intoxication), the concentration of chaperones in the cell increases sharply. Therefore, such molecules are also called stress proteins, or heat shock proteins... Violation of the structuring of a protein molecule leads to the formation of chemically inert conglomerates, which are deposited in the cell or outside it during amyloidosis, Alzheimer's disease, etc. will be defective. This situation occurs in the so-called prion diseases (scrapie in sheep, rabies in cows, kuru, Creutzfeldt-Jakob disease in humans), when a defect in one of the membrane proteins of a nerve cell causes the subsequent accumulation of inert masses inside the cell and disruption of its vital activity.
Violation of the synthesis processes in the cell can occur at various stages: transcription of RNA in the nucleus, translation of polypeptides in ribosomes, post-translational modification, hypermethylation and glycosylation of the runway molecule, transport and distribution of proteins in the cell and their excretion. In this case, an increase or decrease in the number of ribosomes, the disintegration of polyribosomes, the expansion of the cisterns of the granular endoplasmic reticulum, the loss of ribosomes by it, the formation of vesicles and vacuoles can be observed. So, in case of poisoning with a pale toadstool, the enzyme RNA polymerase is damaged, which disrupts transcription. Diphtheria toxin, inactivating the elongation factor, disrupts translation processes, causing damage to the myocardium. Infectious agents can be the reason for the violation of the synthesis of some specific protein molecules. For example, herpes viruses inhibit the synthesis and expression of MHC antigen molecules, which allows them to partially avoid immune control, plague bacilli inhibit the synthesis of acute inflammation mediators. The appearance of unusual proteins can stop their further degradation and lead to the accumulation of inert or even toxic material. Violation of decay processes can also contribute to this to a certain extent.
Disruption of decay processes
Simultaneously with the synthesis of protein in the cell, its disintegration occurs continuously. Under normal conditions, this has an important regulatory and formative significance, for example, during the activation of inactive forms of enzymes, protein hormones, proteins of the mitotic cycle. Normal cell growth and development requires a finely controlled balance between the synthesis and degradation of proteins and organelles. However, in the process of protein synthesis, due to errors in the operation of the synthesizing apparatus, abnormal structuring of a protein molecule, its damage by chemical and bacterial agents, a rather large number of defective molecules are constantly formed. According to some estimates, their share is about a third of all synthesized proteins.
Mammalian cells have several main ways of degradation of proteins: through lysosomal proteases (pentidhydrolases), calcium-dependent proteinases (endopeptidases) and the proteasome system. In addition, there are also specialized proteinases, such as caspases. The main organelle in which the degradation of substances in eukaryotic cells occurs is the lysosome, which contains numerous hydrolytic enzymes. Due to the processes of endocytosis and various types of autophagy in lysosomes and phagolysosomes, both defective protein molecules and whole organelles are destroyed: damaged mitochondria, areas of the plasma membrane, some extracellular proteins, the contents of secretory granules.
An important mechanism of protein degradation is the proteasome - a multicatalytic proteinase structure of a complex structure, localized in the cytosol, nucleus, endoplasmic reticulum, and on the cell membrane. This enzyme system is responsible for breaking down damaged proteins as well as healthy proteins that must be removed for the cell to function properly. In this case, the proteins to be destroyed are pre-combined with a specific polypeptide ubiquitin. However, non-ubiquitous proteins can be partially destroyed in proteasomes. The breakdown of a protein molecule in proteasomes to short polypeptides (processing) with their subsequent presentation together with MHC type I molecules is an important link in the implementation of immune control of antigenic homeostasis of the body. With the weakening of the proteasome function, the accumulation of damaged and unnecessary proteins occurs, accompanying cell aging. Violation of the degradation of cyclin-dependent proteins leads to a violation cell division, degradation of secretory proteins - to the development of cystofibrosis. Conversely, an increase in proteasome function accompanies the depletion of the body (AIDS, cancer).
With genetically determined violations of protein degradation, the body is not viable and dies in the early stages of embryogenesis. If the breakdown of fats or carbohydrates is disturbed, then accumulation diseases (thesaurismosis) occur. At the same time, an excess amount of certain substances or products of their incomplete decay - lipids, polysaccharides - accumulates inside the cell, which significantly damages the function of the cell. This is most often observed in liver epitheliocytes (hepatocytes), neurons, fibroblasts and macrophagocytes.
Acquired disorders of the decomposition of substances can occur as a result of pathological processes (for example, protein, fat, carbohydrate and pigment dystrophy) and be accompanied by the formation of unusual substances. Disturbances in the lysosomal proteolysis system lead to a decrease in adaptation during starvation or increased stress, to the occurrence of some endocrine dysfunctions - a decrease in the level of insulin, thyroglobulin, cytokines and their receptors. Disorders of protein degradation slow down the rate of wound healing, cause the development of atherosclerosis, and affect the immune response. During hypoxia, changes in intracellular pH, radiation injury, characterized by increased peroxidation of membrane lipids, as well as under the influence of lysosomotropic substances - bacterial endotoxins, metabolites of toxic fungi (sporofusarin), silicon oxide crystals - the stability of the lysosomal membrane changes, activated lysosomal enzymes are released into the cytoplasm , which causes the destruction of cell structures and death.
CELL
EPITELIAL TISSUE.
TYPES OF FABRICS.
STRUCTURE AND PROPERTIES OF THE CELL.
LECTURE No. 2.
1. The structure and basic properties of the cell.
2. The concept of fabrics. Types of fabrics.
3. The structure and function of epithelial tissue.
4. Types of epithelium.
Purpose: to know the structure and properties of cells, types of tissues. To present the classification of the epithelium and its location in the body. To be able to distinguish epithelial tissue by morphological characteristics from other tissues.
1. A cell is an elementary living system, the basis of the structure, development and life of all animals and plants. Cell science - cytology (Greek sytos - cell, logos - science). The zoologist T. Schwann in 1839 was the first to formulate the cell theory: the cell is the basic unit of the structure of all living organisms, the cells of animals and plants are similar in structure, there is no life outside the cell. Cells exist as independent organisms (protozoa, bacteria), and in the composition of multicellular organisms, in which there are germ cells that serve for reproduction, and body cells (somatic), different in structure and function (nerve, bone, secretory, etc.) Human cell sizes range from 7 microns (lymphocytes) to 200-500 microns (female ovum, smooth myocytes). Any cell contains proteins, fats, carbohydrates, nucleic acids, ATP, mineral salts and water. From inorganic substances the cell contains the most water (70-80%), from organic - proteins (10-20%). The main parts of the cell are: the nucleus, cytoplasm, cell membrane (cytolemma).
NUCLEUS OF CYTOPLASM CYTOLEMM
Nucleoplasm - hyaloplasm
1-2 nucleoli - organelles
Chromatin (endoplasmic reticulum
complex KTolji
cell center
mitochondria
lysosomes
special purpose)
Inclusions.
The cell nucleus is located in the cytoplasm and is delimited from it by the nuclear
shell - nucleolemma. It serves as a place of concentration of genes,
the main chemical which is DNA. The nucleus regulates the formative processes of the cell and all its vital functions. Nucleoplasm provides interaction of various nuclear structures, nucleoli are involved in the synthesis of cellular proteins and some enzymes, chromatin contains chromosomes with genes - carriers of heredity.
Hyaloplasm (Greek hyalos - glass) - the main plasma of the cytoplasm,
is the true internal environment of the cell. It unites all cellular ultrastructures (nucleus, organelles, inclusions) and ensures their chemical interaction with each other.
Organelles (organelles) are permanent ultrastructures of the cytoplasm that perform certain functions in the cell. These include:
1) endoplasmic reticulum - a system of branched channels and cavities formed by double membranes associated with the cell membrane. On the walls of the channels there are the smallest bodies - ribosomes, which are the centers of protein synthesis;
2) the K. Golgi complex, or the internal mesh apparatus, has meshes and contains vacuoles of various sizes (Latin vacuum - empty), participates in the excretory function of cells and in the formation of lysosomes;
3) the cell center - the cytocenter consists of a spherical dense body - the centrosphere, inside which there are 2 dense bodies - centrioles, interconnected by a bridge. Located closer to the nucleus, takes part in cell division, ensuring an even distribution of chromosomes between daughter cells;
4) mitochondria (Greek mitos - thread, chondros - grain) look like grains, rods, threads. ATP synthesis is carried out in them.
5) lysosomes - vesicles filled with enzymes that regulate
metabolic processes in the cell and have digestive (phagocytic) activity.
6) organelles for special purposes: myofibrils, neurofibrils, tonofibrils, cilia, villi, flagella that perform a specific function of the cell.
Cytoplasmic inclusions are non-permanent formations in the form
granules, drops and vacuoles containing proteins, fats, carbohydrates, pigment.
The cell membrane - cytolemma, or plasmolemma, covers the cell from the surface and separates it from the environment. It is semi-permeable and regulates the entry of substances into and out of the cell.
The intercellular substance is located between the cells. In some tissues, it is liquid (for example, in blood), while in others it consists of an amorphous (structureless) substance.
Any living cell has the following basic properties:
1) metabolism, or metabolism (the main vital property),
2) sensitivity (irritability);
3) the ability to reproduce (self-reproduction);
4) the ability to grow, i.e. an increase in the size and volume of cellular structures and the cell itself;
5) the ability to develop, i.e. the acquisition of specific functions by the cell;
6) secretion, i.e. the release of various substances;
7) movement (leukocytes, histiocytes, sperm)
8) phagocytosis (leukocytes, macrophages, etc.).
2. Tissue is a system of cells similar in origin), structure and function. The composition of tissues also includes tissue fluid and waste products of cells. The doctrine of tissues is called histology (Greek histos - tissue, logos - doctrine, science). In accordance with the characteristics of the structure, function and development, the following types of tissues are distinguished:
1) epithelial, or integumentary;
2) connective (tissues of the internal environment);
3) muscle;
4) nervous.
A special place in the human body is occupied by blood and lymph - a liquid tissue that performs respiratory, trophic and protective functions.
In the body, all tissues are closely interconnected morphologically.
and functional. The morphological connection is due to the fact that different
nye tissues are part of the same organs. Functional connection
manifests itself in the fact that the activity of different tissues that make up
bodies, agreed.
Cellular and non-cellular tissue elements in the process of life
activities wear out and die off (physiological degeneration)
and are restored (physiological regeneration). If damaged
tissues are also restored (reparative regeneration).
However, this process is not the same for all tissues. Epithelial
naya, connective, smooth muscle tissue and blood cells regenerated
They are good. Striated muscle tissue repairs
only under certain conditions. The nerve tissue is restored
only nerve fibers. Division of nerve cells in the body of an adult
person has not been identified.
3. Epithelial tissue (epithelium) is the tissue that covers the surface of the skin, the cornea of the eye, as well as lining all the cavities of the body, the inner surface of the hollow organs of the digestive, respiratory, urogenital systems, is part of most glands of the body. In this regard, the integumentary and glandular epithelium are distinguished.
The integumentary epithelium, being a border tissue, carries out:
1) a protective function, protecting the underlying tissues from various external influences: chemical, mechanical, infectious.
2) the metabolism of the body with the environment, performing the functions of gas exchange in the lungs, absorption in the small intestine, excretion of metabolic products (metabolites);
3) creating conditions for the mobility of internal organs in serous cavities: heart, lungs, intestines, etc.
The glandular epithelium carries out a secretory function, i.e. it forms and secretes specific products - secrets that are used in the processes taking place in the body.
Morphologically, epithelial tissue differs from other body tissues in the following features:
1) it always occupies a borderline position, since it is located on the border of the external and internal environments of the body;
2) it is a layer of cells - epithelial cells, which have a different shape and structure in different types of epithelium;
3) there is no intercellular substance between the cells of the epithelium, and the cells
connected to each other through various contacts.
4) epithelial cells are located on the basement membrane (a plate about 1 micron thick, by which it is separated from the underlying connective tissue. The basement membrane consists of an amorphous substance and fibrillar structures;
5) epithelial cells have polarity, i.e. the basal and apical sections of cells have different structures; "
6) the epithelium does not contain blood vessels, so the nutrition of the cells
carried out by the diffusion of nutrients through the basement membrane from the underlying tissues;
7) the presence of tonofibrils - filamentous structures that give strength to epithelial cells.
4. There are several classifications of the epithelium, which are based on various signs: origin, structure, function. Of these, the most widespread is the morphological classification, taking into account the ratio of cells to the basement membrane and their shape on the free apical (Latin apex - apex) part of the epithelial layer ... This classification reflects the structure of the epithelium, depending on its function.
Monolayer squamous epithelium is represented in the body by endothelium and mesothelium. The endothelium lines the blood vessels, lymphatic vessels, and the chambers of the heart. Mesothelium covers the serous membranes of the peritoneal cavity, pleura and pericardium. Monolayer cubic epithelium lines part of the renal tubules, ducts of many glands and small bronchi. The single-layer prismatic epithelium has the mucous membrane of the stomach, small and large intestine, uterus, fallopian tubes, gallbladder, a number of liver ducts, pancreas, part
tubules of the kidney. In organs where absorption processes take place, epithelial cells have a suction border consisting of a large number of microvilli. A single-layer multi-row ciliated epithelium lines the airways: the nasal cavity, nasopharynx, larynx, trachea, bronchi, etc.
The stratified squamous non-keratinizing epithelium covers the outside of the cornea of the eye and the mucous membrane of the oral cavity and esophagus. The stratified squamous epithelium forms the surface layer of the cornea and is called the epidermis. The transitional epithelium is typical for the urinary organs: the renal pelvis, ureters, Bladder whose walls are subject to significant stretching when filled with urine.
Exocrine glands secrete their secretions in the cavity of internal organs or on the surface of the body. They usually have excretory ducts. Endocrine glands have no ducts and secrete secretions (hormones) into the blood or lymph.
The third stage of evolution is the emergence of a cell.
Molecules of proteins and nucleic acids (DNA and RNA) form a biological cell, the smallest living unit. Biological cells are "building blocks" of all living organisms and contain all the material codes of development.
For a long time, scientists considered the structure of the cell to be extremely simple. The Soviet Encyclopedic Dictionary interprets the concept of a cell as follows: "A cell is an elementary living system, the basis of the structure and life of all animals and plants." It should be noted that the term "elementary" in no way means "simplest" On the contrary, the cell is a unique fractal creation of God, striking in its complexity and at the same time the exceptional coherence of the work of all its elements.
When it was possible to look inside with the help of an electron microscope, it turned out that the structure of the simplest cell is as complex and incomprehensible as the Universe itself. Today it has already been established that "A cell is a special matter of the Universe, a special matter of the Cosmos." One single cell contains information that can fit only in tens of thousands of volumes. Soviet encyclopedia... Those. the cell, among other things, is a huge "bioreservice" of information.
The author of the modern theory of molecular evolution, Manfred Eigen, writes: “In order for a protein molecule to be formed by chance, nature would have to do about 10,130 tests and spend on this the number of molecules that would be enough for 1027 Universes. that the validity of each move could be checked by some sort of selection mechanism, then it took only about 2000 attempts.We come to a paradoxical conclusion: the program for constructing a "primitive living cell" is encoded somewhere at the level of elementary particles.
And how could it be otherwise. Each cell, possessing DNA, is endowed with consciousness, is aware of itself and other cells, and is in contact with the Universe, being, in fact, a part of it. And although the number and variety of cells in the human body is staggering (about 70 trillion), they are all self-similar, just as all the processes taking place in cells are self-similar. In the words of the German scientist Roland Glaser, the design of biological cells is "very well thought out." Who is well thought out by whom?
The answer is simple: proteins, nucleic acids, living cells and all biological systems are the product of the creative activity of the intellectual Creator.
What's interesting: at the atomic level, there is no difference between the chemical composition of the organic and inorganic world. In other words, at the atomic level, a cell is made of the same elements as inanimate nature. The differences are found at the molecular level. In living bodies, along with inorganic substances and water, there are also proteins, carbohydrates, fats, nucleic acids, the enzyme ATP synthase and other low molecular weight organic compounds.
To this day, the cell has literally been disassembled into atoms for the purpose of study. However, it is not possible to create at least one living cell, because to create a cell means to create a particle of the living Universe. Academician V.P. Kaznacheev believes that "a cell is a cosmoplanetary organism ... Human cells are certain systems of ether-torsion biocolliders. Processes unknown to us take place in these biocolliders, materialization of cosmic forms of flows, their cosmic transformation, and due to this, particles materialize."
Water.
Almost 80% of the cell mass is water. According to S. Zenin, Doctor of Biological Sciences, water, due to its cluster structure, is an information matrix for managing biochemical processes. In addition, it is water that is the primary "target" with which the sound frequency vibrations interact. The orderliness of cell water is so high (close to the ordering of a crystal) that it is called a liquid crystal.
Proteins.
Proteins play a huge role in biological life. The cell contains several thousand proteins inherent only in this type of cell (with the exception of stem cells). The ability to synthesize their own proteins is inherited from cell to cell and persists throughout life. In the process of vital activity of the cell, proteins gradually change their structure, their function is impaired. These spent proteins are removed from the cell and replaced with new ones, due to which the vital activity of the cell is preserved.
Let us note, first of all, the building function of proteins, for it is they that are the building material of which the membranes of cells and cellular organelles, the walls of blood vessels, tendons, cartilage, etc. are composed.
The signaling function of proteins is extremely interesting. It turns out that proteins are able to serve as signaling substances, transmitting signals between tissues, cells or organisms. The signaling function is performed by hormone proteins. Cells can interact with each other at a distance using signaling proteins transmitted through the extracellular substance.
Proteins also have a motor function. All types of movement that cells are capable of, for example, muscle contraction, are performed by special contractile proteins. Proteins also perform a transport function. They are able to attach various substances and transfer them from one place of the cell to another. For example, the blood protein hemoglobin attaches oxygen and carries it to all tissues and organs of the body. In addition, a protective function is inherent in proteins. When foreign proteins or cells are introduced into the body, it produces special proteins that bind and neutralize foreign cells and substances. And finally, the energy function of proteins is that with the complete breakdown of 1 g of protein, energy is released in the amount of 17.6 kJ.
Cell structure.
The cell consists of three inseparably interconnected parts: the membrane, the cytoplasm and the nucleus, and the structure and function of the nucleus in different periods of the life of the cell are different. For the life of a cell includes two periods: division, as a result of which two daughter cells are formed, and the period between divisions, which is called interphase.
The cell membrane directly interacts with the external environment and interacts with neighboring cells. It consists of an outer layer and a plasma membrane located below it. The surface layer of animal cells is called the glycocalis. It carries out the connection of cells with the external environment and with all the substances around it. Its thickness is less than 1 micron.
Cell structure
The cell membrane is a very important part of the cell. It holds together all the cellular components and delineates the external and internal environment.
Metabolism is constantly occurring between cells and the external environment. From the external environment, water, various salts in the form of individual ions, inorganic and organic molecules enter the cell. Metabolic products, as well as substances synthesized in the cell: proteins, carbohydrates, hormones, which are produced in the cells of various glands, are removed from the cell into the external environment through the membrane. Transport of substances is one of the main functions of the plasma membrane.
Cytoplasm- an internal semi-liquid environment in which the main metabolic processes take place. Recent studies have shown that the cytoplasm is not a kind of solution, the components of which interact with each other in random collisions. It can be compared to jelly, which begins to "shake" in response to external influences. This is how the cytoplasm perceives and transmits information.
In the cytoplasm, the nucleus and various organelles are located, united by it into one whole, which ensures their interaction and the activity of the cell as a single integral system. The nucleus is located in the central part of the cytoplasm. The entire inner zone of the cytoplasm is filled with the endoplasmic reticulum, which is a cellular organoid: a system of tubules, vesicles and "cisterns" delimited by membranes. The endoplasmic reticulum is involved in metabolic processes, providing the transport of substances from the environment into the cytoplasm and between individual intracellular structures, but its main function is participation in protein synthesis, which is carried out in ribosomes. - round microscopic bodies with a diameter of 15-20 nm. The synthesized proteins first accumulate in the channels and cavities of the endoplasmic reticulum, and then are transported to the organelles and areas of the cell where they are consumed.
In addition to proteins, the cytoplasm also contains mitochondria, small bodies 0.2-7 microns in size, which are called "power stations" of cells. Redox reactions take place in mitochondria, providing cells with energy. The number of mitochondria in one cell is from one to several thousand.
Core- the vital part of the cell, controls the synthesis of proteins and, through them, all physiological processes in the cell. In the nucleus of a non-dividing cell, a nuclear envelope, nuclear juice, nucleolus and chromosomes are distinguished. Continuous exchange of substances between the nucleus and the cytoplasm takes place through the nuclear envelope. Under the nuclear envelope is nuclear juice (a semi-liquid substance), which contains the nucleolus and chromosomes. The nucleolus is a dense, rounded body, the size of which can vary widely, from 1 to 10 microns and more. It consists mainly of ribonucleoproteins; participates in the formation of ribosomes. Usually there are 1-3 nucleoli in a cell, sometimes up to several hundred. The nucleolus contains RNA and protein.
With the appearance of a cell on Earth, Life arose!
To be continued...
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