Cell as elementary structurally functional unit of living

Cell as elementary structurally functional unit of living

1. Formation of cells - high-quality stage of evolution.

2. The Cellular theory and its value for a biotechnology and medicine.

3. Procaryotic and eukaryotic cells.

4. Functional properties of cell as an open system.

5. Specializations and integration of cells of multicellular organisms.

 

A cell is the simplest biological system, apt at self-renewal, self-reproduction and development. It dynamically a bar is opened system, which consists of many correlated elements, functioning of which determines the vital functions of cell not only, but matters for an organism as whole. A cell provides the integrity and self-reproduction due to matters and energies which gets from outside. A cell is basis of structure of procaryotes, one-celled, mushrooms, plants and animals. Concerning procaryotes and the simplest concept a "cell" and "organism" coincide, they are named one-celled. One-celled are also some types of water-plants and mushrooms. Most plants and animals consist of many cells, they are named multicellular. At multicellular organisms cells form fabrics which enter in the complement of organs. The vital functions of cells in multicellular are inferior the co-ordinating influencing of integral organism. Co-ordination for animals is carried out the nervous and endocrine systems, and at plants - by direct cytoplasmic connection between cells and circulatory matters (phytohormones).

All living creatures which propagate oneself a sexual way begin to exist from the moment of confluence of two high-specialized cells - spermatozoon and ovule. The impregnated ovule is maternal for all other cells of human body. The body of the grown man consists more than of 100 trillions of cells. Most these cells - high-specialized, have a different structure, to execute certain functions. But regardless of it every cell must be apt at reproduction, synthesis of necessary macromolecules, to provide itself energy, to react on the unfavorable influencing, co-operate with other cells and etc Community of many functions predetermines likeness of structure more than 200 different types of cells of human body, however cells each it is executed a type only peculiar functions them. In dependence on composition and degree of efficiency, the complexes of organic molecules are able to execute certain functions, directed above all things in support high structural organization of organism.

 

Formation of cells is the high-quality stage of evolution.

Procaryotic of cell appeared on Earth approximately 3,5 milliards of years that is why as a result of spontaneous aggregations of organic molecules and protracted evolution (hypothesis of O.I. Oparin (rice. 1.14)). The deciding stage was appearance of enzymatic (catalytic) of molecular mechanisms. The first cells used catalytic properties of RNK and albumens, but as the matter of heredity was contained only RNK. In the process of complication of structure and functions of cells and piling up of additional catalytic albumens the molecule of RNK was transferable two-stranded DNK which kept genetic information, gave beginning chloroplasts, there were Procaryotic of cyanobacteriae water-plant. A basic argument in behalf of symbiotic hypothesis is that mitochondrion and chloroplasts have own DNK. The origins of eukaryotic cells explain a symbiotic hypothesis, what cell-owner an anaerobe was pursuant to. Passing to the oxybiotic breathing is related to penetration of oxybiotic bacteria in host cell and coexistence with her as mitochondria. Green plants are apt at photosynthesis, that predefined being in their cells of chloroplast. It is considered that symbionts cell-owner that gave beginning chloroplasts, there were Procaryotic of cyanobacteriae water-plant. A basic argument in behalf of symbiotic hypothesis is that mitochondrion and chloroplasts have own DNK.

System of intracellular membranes: smooth and shiny and grainy endoplasmic net, complex Gol'dzhi, nuclear shell - obviously is derivative of external membrane which is able ramify into a cell.

Difficult enough for an answer is a question of origin of genetic material of kernel. Possibly, that it also could appear from symbionts-procaryotes. Multiplying the amount of nuclear DNK took place, presumably, gradually, by transferring of genetic material from the genomes of symbionts in an area, limited a membrane.

Very important was an origin of mitosis as to the mechanism of even division of genetic material and recreation from a generation in the generation of similar cells. As a result of subsequent evolution there was a new mechanism of fission - meiosis that decided the problem of reproduction of multicellular organisms.

Passing to sexual reproduction was instrumental in appearance of combinative changeability that substantially revved up evolution. Due to these processes for a 1 milliard of years of evolution the eukaryotic type of cellular organization stipulated the wide variety of living organisms from the simplest to the man (rice. 1.15).

 

A cellular theory and its value is for a biotechnology and medicine.

     Bases of cellular theory were pawned by the German zoologist T. Shwann (1810 - 1882) in 1839

Substantive provisions of cellular theory:

1) a cell is main structural unit of all organisms (plants and animals);

2) the process of formation of cells predetermines growth, development and differentiation of vegetable and animal fabrics.

Development of cellular theory of R. Virkhov (rice. 1.16) in 1858 R. Virkhov walked up to explaining pathological processes in connection with morphological structures, with certain changes in the structure of cells. Position of R. Virkhov is "every cell - from a cell" brilliantly confirmed subsequent development of biology and is the third position of cellular theory. Position of R. Virkhov that out of cells there is not life, did not lose the value also. For example, primitive forms - viruses are become apt at the active processes of vital functions and reproduction only after penetration in a cell.

Important generalization was assertion, that most value in the vital functions of cells has not shell, but its maintenance: cytoplasm and kernel.

Modern state of cellular theory. To the end of the last century, due to successes of microscopic technique, was found out a difficult structure cells, described organelle, are parts cells which execute different functions, and the ways of formation of new cells are explored (mitosis). Already at the beginning of the XX item the primary value of cellular structures became clear in the transmission of the inherited properties. In this time it is possible to consider confessedly, that a cell is basic structural and functional unit of organization of living.

On the modern stage of development of cytology a cellular theory includes such positions:

- a cell is elementary unit of structure and development of all living organisms;

the cells of all one-celled and multicellular organisms are similar originally (homological), by a structure, chemical composition, basic displays of vital functions;

every new cell appears exceptionally as a result of reproduction of maternal by a division;

at multicellular organisms which develop from one cell - zygote, spores and others like that

     - the different types of cells are formed due to their specialization during individual development of individual and form fabrics;

from fabrics there are organs which are closely associated between itself and inferior the nervously humoral and immune systems of adjusting.

 

Value, cellular theory for a biotechnology and medicine. A cell is unit of pathology. A cell must be known not only as unit of structure of organism but also as unit of pathological changes. Practically all illnesses are the structures and functions of cells which all fabrics and organs appear from related to violation. Violation of structure and function of one cell is primary cause of origin and development of illness, and violation other can be already investigation of unfavorable changes in an organism. For example, at the heart attack of myocardium functioning is violated, and then death of cardiomiozititve comes through the sharp lack of oxygen. By virtue of that part of cardiac muscle does not take part in reduction, blood supply is violated in an organism which results in hypoxia and changes of function and structure of cells, in the first turn of neurons of cerebrum.

Violation of the normal functioning of cells (pathology) is related to many various factors (physical, chemical, and biological) and characterized violations of commons or local of organization of organelle cells, change of separate metabolic processes. Unfavorable for a cell factors can be waves, ionizing a radiation, low and high temperatures, different chemical connections, viral, bacterial and mycotic infections, lack of nutritives or separate physiological active connections (irreplaceable amino acid and fat acids, vitamins and microelements), lack of oxygen and others like that. The negative influencing is inflicted by internal factors, such as which bring mutations over of the inherited material of, to born defects of synthesis of albumens, lipids, surplus products of hormones, violation of utilization of toxic metabolites.

Among the pathological changes of cell it is possible to mark violation of structure and permeability of membranes of mitochondria, lysosomes and other intracellular educations. As a result of the unfavorable influencing mitochondria swell up and acquire the type of blisters, limited only an external membrane. Degeneration and edema is accompanied violation of reactions of redox reaction in mitochondria, by insufficient formation of high-power connections that is negatively reflected on homeostasis of all cell. The similar phenomena meet at saccharine diabetes and starvation in the cells of liver, at the diseases of heart, buds. Reticulum brings pathological changes over of membrane of endoplasmic to violation of synthesis of albumens of cell. These violations meet at failing in the meal of irreplaceable amino acid.

Increase of permeability of membranes of lysosomes, that is observed, for example, at avitaminosis of E, or under act of ionizing an irradiation can strengthen the output of hydrolytic enzymes in a cytoplasm from lysosomes, to result in partial or even complete destruction of cells. At much intoxication the cells of liver or buds are damaged, and violation of functioning of these organs causes the change of other cells of organism through the products of metabolism.

The wide-spread reason of pathology of cell is penetration and reproduction in her of viruses. Thus the processes of exchanges in a cell are violated - a virus forces a cell to work exceptionally "on itself". After mass education and output of viral particles from a cell she perishes. Some pathogenic viruses do not kill a cell, but cause its regeneration. If a factor not fully injured a cell, after stopping of his action a cell can pick up thread the structure and functions. This process is named intracellular repair.

 

Procaryotic and eukaryotic cells.

Five reigns of living organisms are formed two types of cells: Procaryotic, that does not have typical kernels (bacteria and cyanobacteriae water-plants), and eukaryotic, which have peculiar kernels (most, mushrooms and animals one-celled organisms, plant).

Prokaryotes. In prokaryotes, which bacteria and cyanobacteriae water-plants, cells of small sizes belong to (0,5-3 mkm). These cells are deprived nuclear membrane and does not contain expressly designed, limited the membrane of organelle. A kernel and chromosomes is absent in Procaryotic cells. Genetic material is presented one long circular molecule of DNK. It is not discovered histone of albumens, for them nucleosome organization of chromatin is absent. The circular molecule of DNK is packed in a cell as loops. Procaryotic cells surrounded a cellular wall which consists mainly of carbohydrates and amino acid. A plasmatic or cellular membrane forms thrusting out in a cytoplasm, which are named mesosomas, often. They execute the function of formation of ATP - rich on energy connection. In prokaryotes motion of cytoplasm and amoeboid motion absent; they move more frequent in all by plaits, organized considerably simpler from the plaits of eukaryotes. Prokaryotes is widespread practically everywhere. They differ an enormous variety, hasty growth, short sometimes generations. Prokaryotic a cell can test a division through each 20 minuts. And thus to form 10 hours prior to 5 milliards of cells.

Some representatives of prokaryotes:

Mycoplasm - the simplest from cells, by the diameter of about 0,1-0,3 mkm. They are intracellular by them by vermin.

Rickettsia is exciters of the epidemic spotted fever. Middle sizes them 0,3-0,6 mkm.

Coccus are the small rounded bacteria (staphylococcus, gonococci and other) Diameter them 0,8-10 mkm.

Bacilli are rod-like bacteria (intestinal stick, salmonella and other)

Vibrios - after a form remind who, long 1,5-3,0 mkm, in thick 0,3 mkm (choleraic vibrio).

Spirilla - long 3,0-5,0 mkm (exciter of sodoku).

Cyanobacteriae is blue-green water-plants.

 

Eukaryotes. Eukaryotes are organisms, the cells of which have a kernel (from greek. - khariyuu), surrounded a diaphragm shell. The simplest belong to eukaryotes, mushrooms, plants and animals. Genetic material is concentrated mainly in chromosomes which have a difficult structure and formed the filaments of DNK and histonic by albuminous molecules. Hem of cells are mitotic. In a cytoplasm distinguish much characteristic organelles: centrioles, mitochondria, plastids et al. Basic differences between Prokaryotic and it are resulted the eukaryotic types of cells in tabl. 1.1. Among eukaryote there are both one-celled and multicellular organisms to which peculiar difficult principle of structural organization. Forms of cells can be various, sizes hesitate in scopes - from 5 to 100 mkm. Cells have similar chemical composition and exchange of matters. They are distributed the system of membranes on compartments. All cells have the unique system of saving and realization of the inherited information. However much the cells of organisms which belong to the different reigns (animals, plants, mushrooms and simplest) have a row of substantial features. It is shown in tabl. 1.2, where the differences of eukaryotic cells of plants and animals are resulted.

 

Cells of animals

Does not have a hard cellular shell

Can change a form and move

Centrosome is in all cells

A kernel is localized mainly in the center of cell

Can contain shallow vacuoles

Plastids is absent

A lot of mitochondrias

Kristi of mitochondrias laminar

Can not synthesize all amino acid, coenzymes and vitamins

Feed of heterotrophic 

Stock carbohydrates as glycogen

 

Cells of plants

Have a hard cellulose shell

Can not change a form and move

Centrosome is absent Exchange a matter. Between an environment and cells (as by the open systems) there is an exchange molecule. A cell electorally takes in necessary and destroys unnecessary her matters (rice. 1.17). Began to flow matters related above all things to metabolism of cells of, which shows by itself unity of assimilation and dissimilation. Assimilation is a process of "assimilation" of matters which enter cell, to the specific matters, what characteristic for her. It is an endothermic process, that process which requires the charges of energy. It is set that the synthesis of matters in cells takes place due to a metabolic fund which includes: products of the overcooked meal and products of dissimilation, which appear in cells. Began to flow matters in a cell supports stable molecular composition of its cytoplasm which includes for itself inorganic and organic compounds. In a digestive highway a meal is translated in mixture of low-molecular organic matters: amino acid, nucleotides, and carbohydrate-nonspecific and identical for all living nature. In such kind they enter cell and form a metabolic fund. Due to the processes of assimilation two is executed functions are very important: the structure of cell is supported and she is provided energy which acts with organic matters. Dissimilation shows by itself an exothermic process, that a process of liberation of energy is due to disintegration of matters of cell. Matters which appear at dissimilation are also subject subsequent transformation and used a cell.

Exchange energy. In a cell energy, accumulated in chemical copulas between molecules and atoms, acts together with organic matters, which is then freed and transforms in ATP. Energy is needed for support of stability of the cellular system: providing of structure, homeostasis, metabolism and functions. All functions which are executed by a cell require energy which is freed in the process of dissimilation. Exchange energy in the groups of organisms is provided different processes: glycolysis, photosynthesis, chemosynthesis, breathing. For animals basic is a breathing process. It is an aggregate of biochemical reactions of breaking (acescence) up of organic matters (glucose, fat acids, amino acid) to CO₂ and H₂O and use of energy severed chemical connections for formation of high-calorie cellular "fuel" as adenosine diphosphate (ADP). As known, power material in a cell is a molecule of ATP. She accumulates energy, freely moves in a cell and gives energy for realization of endothermic processes. ATP appears as a result of tacking to ADP of the third phosphatic group. The processes of formation of ATP take place on the internal membrane of mitochondrias, which contains the special enzymes, - ATP-sintetaza. Exchange information

1. A cell perceives changes in an environment (signals) and capable on them adequately to react. Due to it a cell can adapt to the changeable terms of existence. It is provided formation of new, necessary in these terms enzymes and other macromolecules. Regulational intracellular processes cause changes of form, sizes and functioning of cells. As a result of result an adequate reaction on the signals of external environment allows a cell to survive in terms which change.

Organization of living is certain related to saving and use of stream of information for support of structurally functional organization of cell and its protracted stable existence as system. The inherited information is saved in the molecules of DNA (deoxyribonucleic acid) as a genetic code - sequence of triplets of nucleotides. Information writes to each other from DNA on the molecules of RNA, which provide the synthesis of necessary structural albumens and enzymes. Squirrels are formed participating to appearance of certain properties of cell. In other words, began to flow information in a cell directed from DNA to the sign:

                                   DNA -» RNA -> albumen -» sign

3.Another informative stream is directed from DNA of one cell to DNA of daughter's cell. This stream is related to the process of reproduction. He will be realized replication of molecules of DNA of maternal cell, formation of chromosomes, process of even division of the inherited material between the cells of daughter’s (mitosis):

                        DNA -» 2 filial DNA -» -> two cells of daughter’s

This stream of information provides a recreation and protracted existence of populations of cells.

Thus, life of cells is supported due to the permanent streams of matters, energy and information.

Specialization and integration of cells of multicellular organisms

Multicellular organisms consist of cells which have an identical structure on principle. However much a form, sizes and structure of cells, depend on functions, what of them execute (rice. 1.18). For example, muscular cells are lengthened, the cells of epithelium fabric are located on a basal membrane, densely adjoin to each other, an intercellular matter is almost absent. Nervous cells due to plenty of sprouts purchased a stellar form. Leucocytes are mobile, rounded form, can take amoeboid shape and etc Thus functionally specialized cell of different types and types of animals the similar have a structure, form and sizes.

Thus, the cells of animals are very various on sizes, structure and functions, what of them execute. However much all cells have basic components necessarily: cytoplasmic membrane, cytoplasm and kernel (except for red corpuscles and Zimmermann's corpuscles which a kernel is absent in).

Basic types of cells of man.  Cell of man - microscopic sizes. The diameter of cells hesitates from 0,01 to 0,1 mm (or from 10 to 100 mkm). A volume of most cells of man is within the limits of 200 - 15000 ìêì3. The diameter of shallow cells of man (red corpuscles, Zimmermann's corpuscles) is evened 4 - 5 mkm (rice. 1.18a). Large enough cells which can be seen with a naked eye are however known. The size of cells depends on functions, what of them execute. Yes, ovules due to piling up in them of nutritives achieve sizes to 150 - 200 mkm.

The sizes of cells are straight unconnected with the size of organism. Yes, the cells of liver and buds for a man, horse, cattle and mouse have an identical size approximately. The sizes of organs, as well as sizes of whole organism of animals and plants, depend on the amount of cells. An amount of cells which make an organism is different: from one (in one-celled) or two-bit (at rotifers and round worms) to many milliards, as in most multicellular. A new-born man contains approximately 2 trillions of cells, adult - 60-100 trillions. A donor which hands over blood loses 5 - 6 milliards of cells. Daily one percent of the cells loses and proceeds in our organism, that approximately 600 milliards.

In the organism of man there are various cells, which differ sizes, structure and functions. Similar after a structure and functions cells, bound by unity of origin, form fabrics. The specialized cells form four types of fabrics: epithelium, connecting, muscle, nervous. Cells which keep the personal touches each as fabric can in wide scopes change both after a structure and after functions. Thus character of divergences changes in the process of individual development of organism. The important factor of structurally functional features is co-operating of cell with other cells, fabrics or remote cellular systems through the nervous system or humoral connection. In every fabric there are cells which keep a capacity for a division. Part from them after a division begins to be differentiated and substitute cells fabrics which die off. The second part of cells remains undifferentiated, well-off to the next divisions (cells of barrels).

 

A question is for self-control and discussion

What mechanisms did decide in appearance of first prokaryotes?

Does essence of symbiotic theory consist in what?

Is there what value of origin of mitosis and meiosis in the evolution of cells?

Is there what value of works of M. Shleinden in substantiation of cellular theory?

What substantive provisions of cellular theory of T. Shvann?

A role of R. Virkhov is in development of cellular theory.

A value of "Cellular pathology" of R. Virkhov is for theoretical and practical medicine.

Are there what substantive provisions of cellular theory on the modern stage of biology?

What does the value of cellular theory consist in forming of clinical thought of doctor?

What organisms do belong to prokaryotes?

Transfer the basic lines of structure of prokaryotes.

Specify basic differences between prokaryotes and eukaryotes, using tabl. 1.1.

What functional properties of cell do characterize her as an open system?

Give description the stream of matters in a cell.

Explain essence of the phenomena of stream of energy: environment ->îðãàí³çì; organism -> environment.

What does essence of exchange of information consist in in the system a "environment is an organism"?

Give determination the processes of specialization and integration of cells in an organism.

What cells do consider barrels?

What do the cells of barrels of embryos and mature differ?

What are the cells of barrels used for in experimental and clinical medicine?