Which scientist discovered cell division? Discovery of the body cell

– an elementary structural and functional unit of all living organisms. It can exist as a separate organism (bacteria, protozoa, algae, fungi) or as part of the tissues of multicellular animals, plants and fungi.

History of the study of cells. Cell theory.

The life activity of organisms at the cellular level is studied by the science of cytology or cell biology. The emergence of cytology as a science is closely related to the creation of cell theory, the broadest and most fundamental of all biological generalizations.

The history of the study of cells is inextricably linked with the development of research methods, primarily with the development of microscopic technology. The microscope was first used to study plant and animal tissues by the English physicist and botanist Robert Hooke (1665). While studying a section of the elderberry core plug, he discovered separate cavities - cells or cells.

In 1674, the famous Dutch researcher Anthony de Leeuwenhoek improved the microscope (magnified 270 times) and discovered single-celled organisms in a drop of water. He discovered bacteria in dental plaque, discovered and described red blood cells and sperm, and described the structure of the heart muscle from animal tissues.

• 1827 - our compatriot K. Baer discovered the egg.
• 1831 - English botanist Robert Brown described the nucleus in plant cells.
• 1838 - German botanist Matthias Schleiden put forward the idea of ​​the identity of plant cells from the point of view of their development.
• 1839 - German zoologist Theodor Schwann made the final generalization that plant and animal cells have a common structure. In his work “Microscopic Studies on the Correspondence in the Structure and Growth of Animals and Plants,” he formulated the cell theory, according to which cells are the structural and functional basis of living organisms.
• 1858 - German pathologist Rudolf Virchow applied the cell theory in pathology and supplemented it with important provisions:

1) a new cell can only arise from a previous cell;

2) human diseases are based on a violation of the structure of cells.

Cell theory in its modern form includes three main provisions:

1) cell - the elementary structural, functional and genetic unit of all living things - the primary source of life.

2) new cells are formed as a result of the division of previous ones; A cell is an elementary unit of living development.

3) the structural and functional units of multicellular organisms are cells.

Cell theory has had a fruitful influence on all areas of biological research.

The first person to see cells was an English scientist Robert Hooke(known to us thanks to Hooke's law). IN 1665 trying to understand why Cork tree swims so well, Hooke began to examine thin sections of cork with the help of his improved microscope. He discovered that the cork was divided into many tiny cells, which reminded him of monastery cells, and he called these cells cells (in English cell means “cell, cell, cell”). IN 1675 Italian doctor M. Malpighi, and in 1682- English botanist N. Grew confirmed the cellular structure of plants. They began to talk about the cell as “a vial filled with nutritious juice.” IN 1674 Dutch master Anthony van Leeuwenhoek(Anton van Leeuwenhoek, 1632 -1723 ) using a microscope for the first time I saw “animals” in a drop of water - moving living organisms ( ciliates, amoebas, bacteria). Leeuwenhoek was also the first to observe animal cells - red blood cells And spermatozoa. Thus, by the beginning of the 18th century, scientists knew that under high magnification plants have a cellular structure, and they saw some organisms that were later called unicellular. IN 1802 -1808 years French explorer Charles-Francois Mirbel established that all plants consist of tissues formed by cells. J. B. Lamarck V 1809 extended Mirbel's idea of ​​cellular structure to animal organisms. In 1825, a Czech scientist J. Purkinė discovered the nucleus of the egg cell of birds, and in 1839 introduced the term " protoplasm" In 1831, an English botanist R. Brown first described the nucleus of a plant cell, and in 1833 established that the nucleus is an obligatory organelle of the plant cell. Since then, the main thing in the organization of cells has been considered not to be the membrane, but the contents. Cell theory the structure of organisms was formed in 1839 German zoologist T. Schwann And M. Schleiden and included three provisions. In 1858 Rudolf Virchow supplemented it with one more position, however, there were a number of errors in his ideas: for example, he assumed that cells were weakly connected to each other and each existed “on its own.” Only later was it possible to prove the integrity of the cellular system. IN 1878 Russian scientists I. D. Chistyakov open mitosis in plant cells; V 1878 V. Flemming and P. I. Peremezhko discover mitosis in animals. IN 1882 V. Flemming observes meiosis in animal cells, and in 1888 E Strasburger - from plants.

18. Cell theory- one of the generally recognized biological generalizations that affirm the unity of the principle of the structure and development of the world plants, animals and other living organisms with cellular structure, in which the cell is considered as a common structural element of living organisms.

19. Basic principles of cell theory

Modern cell theory includes the following basic principles:

No. 1 The cell is a unit of structure, vital activity, growth and development of living organisms; there is no life outside the cell;

No. 2 A cell is a single system consisting of many elements naturally interconnected with each other, representing a certain integral formation;

No. 3 The cells of all organisms are similar in their chemical composition, structure and functions;

No. 4 New cells are formed only as a result of the division of original cells;

No. 5 Cells of multicellular organisms form tissues, and tissues form organs. The life of an organism as a whole is determined by the interaction of its constituent cells;

No. 6 Cells of multicellular organisms have a full set of genes, but differ from each other in that different groups of genes work in them, which results in morphological and functional diversity of cells - differentiation.

Development of cell theory in the second half of the 19th century

Since the 1840s, the study of the cell has become the focus of attention throughout biology and has been rapidly developing, becoming an independent branch of science - cytology.

For the further development of cell theory, its extension to protists (protozoa), which were recognized as free-living cells, was essential (Siebold, 1848).

At this time, the idea of ​​the composition of the cell changes. The secondary importance of the cell membrane, which was previously recognized as the most essential part of the cell, is clarified, and the importance of protoplasm (cytoplasm) and the cell nucleus is brought to the fore (Mol, Cohn, L. S. Tsenkovsky, Leydig, Huxley), which is reflected in the definition of a cell given by M. Schulze in 1861:

A cell is a lump of protoplasm with a nucleus contained inside.

In 1861, Brücko put forward a theory about the complex structure of the cell, which he defines as an “elementary organism,” and further elucidated the theory of cell formation from a structureless substance (cytoblastema), developed by Schleiden and Schwann. It was discovered that the method of formation of new cells is cell division, which was first studied by Mohl on filamentous algae. The studies of Negeli and N.I. Zhele played a major role in refuting the theory of cytoblastema using botanical material.

Tissue cell division in animals was discovered in 1841 by Remarque. It turned out that the fragmentation of blastomeres is a series of successive divisions (Bishtuf, N.A. Kölliker). The idea of ​​the universal spread of cell division as a way of forming new cells is enshrined by R. Virchow in the form of an aphorism:

"Omnis cellula ex cellula." Every cell from a cell.

In the development of cell theory in the 19th century, contradictions arose sharply, reflecting the dual nature of cellular theory, which developed within the framework of a mechanistic view of nature. Already in Schwann there is an attempt to consider the organism as a sum of cells. This tendency receives special development in Virchow’s “Cellular Pathology” (1858).

Virchow’s works had a controversial impact on the development of cellular science:

He extended the cell theory to the field of pathology, which contributed to the recognition of the universality of cellular theory. Virchow's works consolidated the rejection of the theory of cytoblastema by Schleiden and Schwann and drew attention to the protoplasm and nucleus, recognized as the most essential parts of the cell.

Virchow directed the development of cell theory along the path of a purely mechanistic interpretation of the organism.

Virchow elevated cells to the level of an independent being, as a result of which the organism was considered not as a whole, but simply as a sum of cells.

XXcentury

Since the second half of the 19th century, cell theory has acquired an increasingly metaphysical character, reinforced by Verworn’s “Cellular Physiology,” which considered any physiological process occurring in the body as a simple sum of the physiological manifestations of individual cells. At the end of this line of development of cell theory, the mechanistic theory of the “cellular state” appeared, including Haeckel as a proponent. According to this theory, the body is compared to the state, and its cells are compared to citizens. Such a theory contradicted the principle of the integrity of the organism.

The mechanistic direction in the development of cell theory was subjected to severe criticism. In 1860, I.M. Sechenov criticized Virchow’s idea of ​​the cell. Later, the cell theory was criticized by other authors. The most serious and fundamental objections were made by Hertwig, A. G. Gurvich (1904), M. Heidenhain (1907), Dobell (1911). The Czech histologist Studnicka (1929, 1934) made extensive criticism of the cellular theory.

In the 1950s, a Soviet biologist O. B. Lepeshinskaya, based on the data of her research, put forward a “new cell theory” as opposed to “Virchowianism.” It was based on the idea that in ontogenesis, cells can develop from some non-cellular living substance. A critical verification of the facts laid down by O. B. Lepeshinskaya and her adherents as the basis for the theory she put forward did not confirm the data on the development of cell nuclei from nuclear-free “living matter”.

Modern cell theory

Modern cellular theory proceeds from the fact that cellular structure is the most important form of existence of life, inherent in all living organisms, except viruses. The improvement of cellular structure was the main direction of evolutionary development in both plants and animals, and the cellular structure is firmly retained in most modern organisms.

At the same time, the dogmatic and methodologically incorrect provisions of the cell theory must be re-evaluated:

Cellular structure is the main, but not the only form of existence of life. Viruses can be considered non-cellular life forms. True, they show signs of life (metabolism, ability to reproduce, etc.) only inside cells; outside cells, the virus is a complex chemical substance. According to most scientists, in their origin, viruses are associated with the cell, they are part of its genetic material, “wild” genes.

It turned out that there are two types of cells - prokaryotic (cells of bacteria and archaebacteria), which do not have a nucleus delimited by membranes, and eukaryotic (cells of plants, animals, fungi and protists), which have a nucleus surrounded by a double membrane with nuclear pores. There are many other differences between prokaryotic and eukaryotic cells. Most prokaryotes do not have internal membrane organelles, and most eukaryotes have mitochondria and chloroplasts. According to the theory of symbiogenesis, these semi-autonomous organelles are descendants of bacterial cells. Thus, a eukaryotic cell is a system of a higher level of organization; it cannot be considered entirely homologous to a bacterial cell (a bacterial cell is homologous to one mitochondria of a human cell). The homology of all cells, thus, has been reduced to the presence of a closed outer membrane made of a double layer of phospholipids (in archaebacteria it has a different chemical composition than in other groups of organisms), ribosomes and chromosomes - hereditary material in the form of DNA molecules forming a complex with proteins . This, of course, does not negate the common origin of all cells, which is confirmed by the commonality of their chemical composition.

The cellular theory considered the organism as a sum of cells, and the life manifestations of the organism were dissolved in the sum of the life manifestations of its constituent cells. This ignored the integrity of the organism; the laws of the whole were replaced by the sum of the parts.

Considering the cell to be a universal structural element, the cell theory considered tissue cells and gametes, protists and blastomeres as completely homologous structures. The applicability of the concept of a cell to protists is a controversial issue in cellular theory in the sense that many complex multinucleated protist cells can be considered as supracellular structures. In tissue cells, germ cells, and protists, a general cellular organization is manifested, expressed in the morphological separation of karyoplasm in the form of a nucleus, however, these structures cannot be considered qualitatively equivalent, taking all their specific features beyond the concept of “cell”. In particular, gametes of animals or plants are not just cells of a multicellular organism, but a special haploid generation of their life cycle, possessing genetic, morphological, and sometimes environmental characteristics and subject to the independent action of natural selection. At the same time, almost all eukaryotic cells undoubtedly have a common origin and a set of homologous structures - cytoskeletal elements, eukaryotic-type ribosomes, etc.

The dogmatic cell theory ignored the specificity of non-cellular structures in the body or even recognized them, as Virchow did, as non-living. In fact, in the body, in addition to cells, there are multinuclear supracellular structures ( syncytia, simplasts) and a nuclear-free intercellular substance that has the ability to metabolize and is therefore alive. To establish the specificity of their life manifestations and their significance for the body is the task of modern cytology. At the same time, both multinuclear structures and extracellular substance appear only from cells. Syncytia and symplasts of multicellular organisms are the product of the fusion of the original cells, and the extracellular substance is the product of their secretion, i.e. it is formed as a result of cell metabolism.

The problem of the part and the whole was resolved metaphysically by the orthodox cell theory: all attention was transferred to the parts of the organism - cells or “elementary organisms”.

The integrity of the organism is the result of natural, material relationships that are completely accessible to research and discovery. The cells of a multicellular organism are not individuals capable of existing independently (the so-called cell cultures outside the body are artificially created biological systems). As a rule, only those multicellular cells that give rise to new individuals (gametes, zygotes or spores) and can be considered as separate organisms are capable of independent existence. A cell cannot be separated from its environment (as, indeed, any living systems). Focusing all attention on individual cells inevitably leads to unification and a mechanistic understanding of the organism as a sum of parts.

Cleared of mechanism and supplemented with new data, the cell theory remains one of the most important biological generalizations.

The first person to see cells was an English scientist Robert Hooke(known to us thanks to Hooke's law). IN 1665 trying to understand why Cork tree swims so well, Hooke began to examine thin sections of cork with the help of his improved microscope. He discovered that the cork was divided into many tiny cells, which reminded him of monastery cells, and he called these cells cells (in English cell means “cell, cell, cell”). IN 1675 Italian doctor M. Malpighi, and in 1682- English botanist N. Grew confirmed the cellular structure of plants. They began to talk about the cell as “a vial filled with nutritious juice.” IN 1674 Dutch master Anthony van Leeuwenhoek(Anton van Leeuwenhoek, 1632 -1723 ) using a microscope for the first time I saw “animals” in a drop of water - moving living organisms ( ciliates, amoebas, bacteria). Leeuwenhoek was also the first to observe animal cells - red blood cells And spermatozoa. Thus, by the beginning of the 18th century, scientists knew that under high magnification plants have a cellular structure, and they saw some organisms that were later called unicellular. IN 1802 -1808 French explorer Charles-Francois Mirbel established that all plants consist of tissues formed by cells. J. B. Lamarck V 1809 extended Mirbel's idea of ​​cellular structure to animal organisms. In 1825, a Czech scientist J. Purkinė discovered the nucleus of the egg cell of birds, and in 1839 introduced the term " protoplasm" In 1831, an English botanist R. Brown first described the nucleus of a plant cell, and in 1833 established that the nucleus is an obligatory organelle of the plant cell. Since then, the main thing in the organization of cells has been considered not to be the membrane, but the contents.
Cell theory the structure of organisms was formed in 1839 German zoologist T. Schwann And M. Schleiden and included three provisions. In 1858 Rudolf Virchow supplemented it with one more position, however, there were a number of errors in his ideas: for example, he assumed that cells were weakly connected to each other and each existed “on its own.” Only later was it possible to prove the integrity of the cellular system.
IN 1878 Russian scientists I. D. Chistyakov open mitosis in plant cells; V 1878 V. Flemming and P. I. Peremezhko discover mitosis in animals. IN 1882 V. Flemming observes meiosis in animal cells, and in 1888 E Strasburger - from plants.

18. Cell theory- one of the generally recognized biological generalizations that affirm the unity of the principle of the structure and development of the world plants, animals and other living organisms with cellular structure, in which the cell is considered as a common structural element of living organisms.

The study of the smallest structures of living organisms became possible only after the invention of the microscope, i.e. after 1600. The first description and images of cells were given in 1665 by the English botanist R. Hooke: examining thin sections of dried cork, he discovered that they “consist of many boxes.” Hooke called each of these boxes a cell (“chamber”). The Italian researcher M. Malpighi (1674), the Dutch scientist A. van Leeuwenhoek, and the Englishman N. Grew (1682) soon provided a lot of data demonstrating the cellular structure of plants. However, none of these observers realized that the really important substance was the gelatinous material that filled the cells (later called protoplasm), and the “cells” that seemed so important to them were simply lifeless cellulose boxes that contained this substance. Until the middle of the 19th century. In the works of a number of scientists, the beginnings of a certain “cellular theory” as a general structural principle were already visible. In 1831, R. Brown established the existence of a nucleus in a cell, but failed to appreciate the full importance of his discovery. Soon after Brown's discovery, several scientists became convinced that the nucleus was immersed in the semi-liquid protoplasm filling the cell. Initially, the basic unit of biological structure was considered to be fiber. However, already at the beginning of the 19th century. Almost everyone began to recognize a structure called a vesicle, globule or cell as an indispensable element of plant and animal tissues. Novosibirsk installation of video surveillance in the house price brondavideo

Creation of cell theory. The amount of direct information about the cell and its contents increased enormously after 1830, when improved microscopes became available. Then, in 1838–1839, what is called “the master’s finishing touch” happened. The botanist M. Schleiden and the anatomist T. Schwann almost simultaneously put forward the idea of ​​cellular structure. Schwann coined the term "cell theory" and introduced this theory to the scientific community. According to the cellular theory, all plants and animals consist of similar units - cells, each of which has all the properties of a living thing. This theory has become the cornerstone of all modern biological thinking.

Discovery of protoplasm. At first, undeservedly much attention was paid to the cell walls. However, F. Dujardin (1835) described living jelly in unicellular organisms and worms, calling it “sarcoda” (i.e., “resembling meat”).

This viscous substance was, in his opinion, endowed with all the properties of living things. Schleiden also discovered a fine-grained substance in plant cells and called it “plant mucilage” (1838). Eight years later, G. von Mohl used the term “protoplasm” (used in 1840 by J. Purkinje to designate the substance from which animal embryos are formed in the early stages of development) and replaced the term “plant mucus” with it. In 1861, M. Schultze discovered that sarcoda is also found in the tissues of higher animals and that this substance is identical both structurally and functionally to the so-called. plant protoplasm. For this “physical basis of life,” as T. Huxley later defined it, the general term “protoplasm” was adopted. The concept of protoplasm played an important role in its time; however, it became clear long ago that protoplasm is not homogeneous either in its chemical composition or in structure, and this term gradually fell out of use. Currently, the main components of a cell are usually considered to be the nucleus, cytoplasm and cellular organelles. The combination of cytoplasm and organelles practically corresponds to what the first cytologists had in mind when speaking of protoplasm.

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The history of the discovery and study of cells. Cell theory

People learned about the existence of cells after the invention of the microscope. The very first primitive microscope was invented by the Dutch glass grinder Z. Jansen (1590), by connecting two lenses together.

The English physicist and botanist R. Hooke, having examined a section of cork oak, discovered that it consists of cells similar to honeycombs, which he called cells (1665). Yes, yes... this is the same Hooke, after whom the famous physical law is named.

Rice. "A section of balsa wood from the book of Robert Hooke, 1635-1703"

In 1683, the Dutch researcher A. Van Leeuwenhoek, having improved the microscope, observed living cells and described bacteria for the first time.

Russian scientist Karl Baer discovered the mammalian egg in 1827. With this discovery, he confirmed the previously expressed idea of ​​the English physician W. Harvey that all living organisms develop from eggs.

The nucleus was first discovered in plant cells by the English biologist R. Brown (1833).

The works of German scientists: botanist M. Schleiden and zoologist T. Schwann were of great importance for understanding the role of cells in living nature. They were the first to formulate cell theory, the main point of which stated that all organisms, including plants and animals, consist of the simplest particles - cells, and each cell is an independent whole. However, in the body, cells act together to form a harmonious unity.

Later in cell theory new discoveries were added. In 1858, the German scientist R. Virchow substantiated that all cells are formed from other cells through cell division: “every cell is from a cell.”

Cell theory served as the basis for the emergence in the 19th century.

History of the discovery of the cell nucleus

science of cytology. By the end of the 19th century. Thanks to the increasing sophistication of microscopic technology, the structural components of cells and the process of their division were discovered and studied. The electron microscope made it possible to study the finest cell structures. An amazing similarity was discovered in the fine structure of cells of representatives of all kingdoms of living nature.

Basic provisions of modern cell theory:

• cell is a structural and functional unit of all living organisms, as well as a unit of development;
• cells have a membrane structure;
• nucleus - the main part of a eukaryotic cell;
• cells reproduce only by division;
• The cellular structure of organisms indicates that plants and animals have the same origin.

1. Cytoplasm2. Functions of the cytoplasm or the role of the cytoplasm in the cell3. The structure of the cytoplasm4. Movement of cytoplasm5. Cytoplasmic organelles6. Composition of the cytoplasm

Cytoplasm- This is the internal environment of the cell, limited by the cell membrane, except for the nucleus and vacuole. It was previously said that the cell consists of 80% water. A feature of the structure of the cell cytoplasm is that most of the cell’s water structure is in the cytoplasm. The solid part of the cytoplasm includes proteins, carbohydrates, phospholipids, cholesterol and other nitrogen-containing organic compounds, mineral salts, inclusions in the form of glycogen droplets (in animal cells) and other substances.

§ 10. History of the discovery of the cell. Creation of cell theory

Almost all processes of cellular metabolism take place in the cytoplasm. The cytoplasm also contains reserve nutrients and insoluble waste products from metabolic processes.

Functions of the cytoplasm or role of the cytoplasm:
1. Connect all parts of the cell into a single whole;
2. Chemical processes take place in it;
3. Transports substances;
4. Performs a support function.

TO structural features of the cytoplasm the following can be attributed:
1. Colorless viscous substance;
2. Is in constant motion;
3. Contains organelles (permanent structural components and cellular inclusions, and non-permanent structural cells);
4. Inclusions can be in the form of drops (fats) and grains (proteins and carbohydrates).

You can see what the cytoplasm looks like using the example of the structure of a plant cell or animal cell.

The movement of cytoplasm in the cell is virtually continuous. The movement of the cytoplasm itself is carried out due to the cytoskeleton, or more precisely due to changes in the shape of the cytoskeleton.

Organoids of the cell cytoplasm include all organoids located in the cell, since they are all located inside the cytoplasm. All organelles in the cytoplasm are in a mobile state and can move due to the cytoskeleton.

The composition of the cytoplasm includes:
1. Water approximately 80%;
2. Protein about 10%;
3. Lipids about 2%;
4. Organic salts about 1%;
5. Inorganic salts 1%;
6. RNA approximately 0.7%;
7. DNA approximately 0.4%.
The above composition of the cytoplasm is true for eukaryotic cells.

The discovery of the cell was preceded by the invention of the microscope at the end of the 16th century (Z. Jansen).

The first person to see cells was R. Hooke (1665). Using a magnifying device, he examined sections of tissue of living organisms. On a cut of a plant plug, he saw a cellular structure and called the individual cells cells. Hooke believed that the cells themselves are empty, and the contents of a living organism are enclosed in a frame (cell wall).

A little later, A. Leeuwenhoek, using a more advanced microscope, saw exactly the contents of the cells, including bacteria.

In 1827, K. Baer discovered the egg, thereby proving the assumption that all living organisms develop from a cell.

A few years later, the nucleus contained in the cell was discovered (R. Brown).

Summarizing the previously made discoveries, T. Schwann developed the first version of the cellular theory, which proved the unity of the cellular structure of plants and animals. However, there was one erroneous assumption in Schwann's cell theory, which was borrowed from another cell researcher - M. Schleiden. Both scientists believed that cells could be formed from non-cellular structures and substances.

In the middle of the 19th century R.

Opening the cell

Virchow proved that all cells are formed only from other cells by dividing them (“each cell from a cell”).

At the same time, the science of cytology emerged, which studies the structure and processes in cells.

In the second half of the 19th century, many components of the cell were discovered, and the role of the nucleus in cell division was noted.

In the first half of the 20th century, other smaller cell structures were discovered using an electron microscope. It became obvious that cells from different organisms and different tissues have much in common.

HISTORY OF BIOLOGY FROM ANCIENT TIMES TO THE BEGINNING OF THE XX CENTURY

Blyakher L.Ya.

MICROSCOPIC STUDY OF THE STRUCTURE AND DEVELOPMENT OF ORGANISMS

Moscow, "Science", 1972

First descriptions of cells

The idea of ​​the discreteness of animal and plant organisms, i.e., of their construction from separate units, sometimes called “cells” (R. Hooke), sometimes “bags” or “bubbles” (M. Malpighi, N. Grew), sometimes “grains” "(K. Wolf), for a long time remained devoid of specific content, since nothing was known about the nature of these formations. The descriptions of F. Fontana (1781), who saw and depicted nuclei and even nucleoli in eel skin cells, went unnoticed; Fontana, of course, was far from understanding the meaning and significance of his observations. Even at the beginning of the 19th century. abstract views were extended to the microscopic structure of organized bodies. For example, in the “Textbook of Natural Philosophy” (1809) by L. Oken, living bodies were described as accumulations of particles, which he called “organic crystals”, “mucous vesicles”, “organic points”, “galvanic vesicles” and even “ciliates”.

The invention of the achromatic microscope and the constant improvement of its optical capabilities made it possible to approach the study of the true structure of cells, primarily plant ones; At first, we were able to see the most noticeable structural formation in them - the shell. It became possible to talk about the true discreteness of the body of higher plants only after in 1812 the German botanist Moldenhauer managed to separate their constituent cells from each other using the method of maceration.

Kernel discovery

Purkin's germinal vesicle. From Purkin's work on the development of the chicken egg (1825)

The cell nucleus, which Fontana first saw in animal cells, was rediscovered in 1825 in an unhatched chicken egg (Ya. Purkin), and in 1831-1832 in plant cells (F. Mirbel). R. Brown (1833) showed that the nucleus is an essential component of every cell. The terms “nucleus” and “nucleolus” were introduced by Purkin’s student G. Valentin; however, Purkin and his collaborators had no idea about the significance of these formations. Soon the cell nucleus attracted the close attention of F. Meyen (1828), M. Schleiden (1838) and T. Schwann (1839). It was Schleiden who owned the erroneous theory of new cell formation, in which he attached decisive importance to the nucleus, therefore calling it cytoblast (cell-forming agent).

Creation of cell theory

The turn of the 30s and 40s of the XIX century. was marked by a fundamental generalization called the cell theory. Speaking about the achievements of natural science in the first half and mid-nineteenth century, F. Engels put forward “three great discoveries” in the first place: along with the proof of the conservation and transformation of energy and Darwin’s evolutionary theory, Engels named the cell theory. “The veil of secrecy,” he wrote, “that shrouded the process of origin and growth and the structure of organisms was torn away. The miracle, incomprehensible to that time, appeared in the form of a process occurring according to a law that is essentially identical for all multicellular organisms.”

Cell theory, i.e. the doctrine of cells as formations that form the basis of the structure of plant and animal organisms, was prepared gradually. Materials for this generalization were accumulated in the studies of J. Purkinė and his students, especially G. Valentin, in the works of the school of I. Müller, in particular in the works of J. Henle. E. Gurlt (1835) compared the cells of the Malpighian layer of the epidermis with plant cells, and A. Donna (1837). At the same time, differences between the cells of plant and animal organisms have been repeatedly noted. Even Purkin, who came closest to the formulation of the cell theory, believed that the “grains” that make up animal tissues are not identical to the “cells” of plants, since in plant cells an important distinguishing feature is the membrane surrounding the cell cavity, and in animal cells lack a noticeable shell and are filled with granular contents.

T.

17. History of the discovery of cells

In the literature devoted to the history of cell theory, a statement has long been made, which is repeated from time to time even today, that the doctrine of cells as structural formations common to plants and animals belongs equally to the botanist M. Schleiden and the zoologist T. Schwann. However, even at the end of the last century, M. Heidenhain, and later F. Studnicka, and especially the Soviet histologist and historian of cell theory Z. S. Katznelson clearly showed that the role of Schleiden and Schwann in the creation of cell theory is unequal. Schwann should be considered the true founder of this theory, who, in addition to the results of his own research, used the observations of Purkin and his students, Schleiden and a number of other botanists and zoologists.

Schwann's cell theory contains three main generalizations - the theory of cell formation, evidence of the cellular structure of all organs and parts of the body, and the extension of these two principles to the growth and development of animals and plants.

The possibility of comparing plant and animal cells and recognizing complete correspondence (homology) between plant and animal cells was a consequence of two provisions from which Schwanl proceeded. He, together with Schleiden, accepted, firstly, that cells are hollow, vesicular formations and, secondly, that in both kingdoms of nature, cells arise from structureless non-cellular matter located inside or between cells; Schwann called the latter cytoblastema. 3. S. Katsnelson expressed a paradoxical and at the same time correct idea that it was these erroneous views on the nature of cells and the method of their origin that allowed Schwann to see their similarities in plants and animals, while a more correct view of animal cells as formations consisting of granular substance and, unlike plant cells, usually devoid of membranes, developed by Purkin, distracted him from the idea of ​​\u200b\u200bthe homology of cells in plants and animals.

Schwann expressed the cell theory as a broad biological generalization in the following words: “The development of the position that for all organic derivatives there is a general principle of formation and that such is cell formation ... can be given the name cell theory.”

Discovery of protoplasm

Further development of cell theory was associated with the study of the internal structure of cells. Purkinet called the basic substance of cells “protoplasm,” at least in relation to animal embryos, and Dujardin, to designate this basic substance, introduced the term sarcoda, which originally referred to the contents of the simplest animals - rhizomes, flagellates and ciliates.

As already noted in Chapter 20, in the late 30s and early 40s there were two points of view on the structure of protozoa. X. Ehrenberg (1838) defended the idea that ciliates have a complex structure comparable to the structure of multicellular animals. Ehrenberg's mistake boils down to the fact that he too straightforwardly compared ciliates with multicellular animals and failed to establish that the numerous “stomachs” of ciliates he described are in fact non-permanent formations, but appearing and disappearing digestive vacuoles. Subsequently, several decades after Ehrenberg, it was found that the structure of ciliates can indeed be very complex.

In contrast to Ehrenberg's opinion, Dujardin defended the elementary structure of ciliates and other single-celled organisms, which, according to his ideas, consist of a sarcoda and are devoid of any organs. The protozoa were separated from other multicellular animals by the German zoologist K. Siebold, author of the “Textbook of Comparative Anatomy of Invertebrate Animals” (1848); however, only after the works of M. Schulpe, A. Kölliker and, especially, E. Haeckel, the idea that the body of protozoa (Protozoa) consists of a single cell, corresponding to the countless cells from which the body of other animals, called multicellular, is built, became universally accepted.

The semi-liquid, granular substance, which, according to Dujardin, fills the body of the simplest animals, was also seen in plant cells. This content of plant cells in the period preceding the creation of the cell theory was discovered by F. Meyen and M. Schleiden, but they did not see in it the carrier of the vital properties of the cell. This was done later, when Hugo von Mol, in his work “On the Movement of Juice within a Cell” (1846), based on observations, proved that protoplasm has the ability to move independently. Mohl's observations on plant cells were confirmed by F. Cohn (1850) and N. Pringsheim (1854). Cohn argued that in terms of optical, physical and chemical properties, capcode, or the contractile substance of animal cells, fully corresponds to the protoplasm of plant cells. F. Leydig in his “Textbook of Histology of Man and Animals” (1857) expressed the idea that the membrane, which was previously considered an essential and most important component of the cell, may often be absent and that the main structural components of the cell are protoplasm and the nucleus.

First assumptions about cell formation

One of the foundations of the cell theory was the idea expressed by Schleiden and accepted by Schwann about the free formation of cells from a structureless substance located inside the cells (Schleiden’s opinion) or outside them in the form of a special cell-forming substance, or cytoblastema (Schwann’s opinion). These ideas about the method of cell formation differed little from the views on this subject of P. Turpin (1827), who believed that grains appearing on the inner surface of the cell membrane turn into young cells and that such a process of cell formation can be repeated indefinitely.

In 1833, Mole expressed an equally unfounded view that new cells “arise... without organic connection with each other and with the maternal organism... from a turbid granular mass suspended in the cell sap.”

Discovery of cell division

Simultaneously with Schleiden’s article, which prompted Schwann to think about a universal method of cell formation and thereby played an important role in the creation of cell theory, Mohl’s work “On the Development of Stomata” (1838) was published, which described the division of cells intended for the formation of guard cells stomata As follows from the drawings in the mentioned work, Moth did not see nuclei either in the stomatal cells or in the mother cells of Anthoceros spores, the division of which he described a year later. At the beginning of the 40s, real knowledge about the method of cell origin was so scarce that the appearance of fantastic descriptions of these phenomena should not be surprising. Thus, A. Griesbach (1844) argued that young cells develop from the primordia of old cells freely floating in the juice, and G. Carsten (1843) accepted the endogenous emergence of cells as the repeated “investment” of cells of successive generations into one another. Schleiden and Schwann were aware of the previously published works of Dumortier (1832) and Mohl (1835), which described the reproduction of filamentous algae cells by division, but they did not attach significance to these descriptions.

Since the beginning of the 40s, botanists (N. I. Zheleznov, F. Unger, K. Nägeli) and zoologists (R. Remak, A. Kölliker, N. A. Warnek) strongly opposed the Schleiden-Schwann theory of cell formation. Their research prepared a generalization formulated by the famous German pathologist R. Virchow in the form of an aphorism: omnis cellula e cellula [each cell (comes only) from a cell].

1. Who owns the discovery of the cell? Who is the author and founder of the cell theory? Who supplemented the cell theory with the principle: “Every cell is from a cell”?

R. Virchow, R. Brown, R. Hooke, T. Schwann, A. van Leeuwenhoek.

The discovery of the cell belongs to R. Hooke.

The principle “Every cell is from a cell” was supplemented by R. Virchow to the cell theory.

2. Which scientists made a significant contribution to the development of ideas about the cell? Name the merits of each of them.

● R. Hooke – discovery of the cell.

● A. van Leeuwenhoek - discovery of single-celled organisms, red blood cells, sperm.

● Ya. Purkin - discovery of the nucleus in an animal cell.

● R. Brown - discovery of the nucleus in plant cells, the conclusion that the nucleus is an essential component of the plant cell.

● M. Schleiden - evidence that the cell is the main structural unit of plants.

● T. Schwann – the conclusion that all living beings consist of cells, the creation of the cellular theory.

● R. Virchow – addition of the cell theory with the principle “Every cell is from a cell.”

3. Formulate the basic principles of cell theory. What contribution did cell theory make to the development of the natural science picture of the world?

1. A cell is an elementary structural and functional unit of living organisms, possessing all the signs and properties of a living thing.

2. The cells of all organisms are similar in structure, chemical composition and basic manifestations of life activity.

3. Cells are formed by division of the original mother cell.

4. In a multicellular organism, cells specialize in function and form tissues. Organs and organ systems are built from tissues.

Cell theory had a significant impact on the development of biology and served as the foundation for the further development of many biological disciplines - embryology, histology, physiology, etc. The basic principles of cell theory have retained their significance to this day.

4. Using the knowledge gained from studying biology in grades 6-9, use examples to prove the validity of the fourth proposition of the cell theory.

For example, the inner (mucosal) lining of the human small intestine includes cells of the integumentary epithelium, which ensure the absorption of nutrients and perform a protective function. Glandular epithelial cells secrete digestive enzymes and other biologically active substances. The middle (muscular) membrane is formed by smooth muscle tissue, the cells of which perform a motor function, causing the mixing of food masses and their movement towards the large intestine. The outer shell is formed by connective tissue that performs a protective function and provides attachment of the small intestine to the posterior wall of the abdomen. Thus, the small intestine is formed by various tissues, the cells of which are specialized to perform certain functions. In turn, the small intestine, together with other organs (esophagus, stomach, etc.) forms the human digestive system.

The cover cells of the leaf skin perform a protective function. Guard and secondary cells form stomatal apparatuses that provide transpiration and gas exchange. Chlorophyll-bearing parenchyma cells carry out photosynthesis.

Discovery of the cell nucleus. Schleiden and his theory of cytogenesis

The veins of the leaf include fibers that impart mechanical strength and conductive tissues, the elements of which ensure the transport of solutions. Consequently, a leaf (plant organ) is formed by different tissues, the cells of which perform certain functions.

5. Before the 1830s. It was widely believed that cells were “bags” with nutritious juice, while the main part of the cell was considered to be its shell. What could be the reason for this idea of ​​cells? What discoveries contributed to changing ideas about the structure and functioning of cells?

The magnifying power of microscopes of that time did not allow a detailed study of the internal contents of cells, but their membranes were clearly visible. Therefore, scientists paid attention primarily to the shape of cells and the structure of their membranes, and considered the internal contents to be “nutritional juice.”

Changing the existing ideas about the structure and functioning of cells was primarily facilitated by the work of J. Purkin (discovered the nucleus in the egg of birds, introduced the concept of “protoplasm”) and R. Brown (described the nucleus in plant cells, came to the conclusion that it is an essential part of the plant cells).

6. Prove that the cell is the elementary structural and functional unit of living organisms.

A cell is an isolated, smallest structure that has all the basic characteristics of a living thing: metabolism and energy, self-regulation, irritability, the ability to grow, develop and reproduce, store hereditary information and transmit it to daughter cells during division. Individual components of the cell do not exhibit all these properties together. All living organisms are made up of cells; outside the cell there is no life. Therefore, the cell is the elementary structural and functional unit of living organisms.

7*. The size of most plant and animal cells is 20-100 microns, i.e. the cells are quite small structures. What determines the microscopic size of cells? Explain why plants and animals do not consist of one (or several) huge cells, but of many small ones.

To maintain vital activity, a cell must constantly exchange substances with its environment. The cell's needs for the supply of nutrients, oxygen, and the removal of final metabolic products are determined by its volume, and the intensity of transport of substances depends on the surface area. Thus, with an increase in cell size, their needs increase in proportion to the cube (x3) of the linear size (x), and the transport of substances “lags behind”, because increases in proportion to the square (x2). As a result, the speed of vital processes in cells is inhibited. Therefore, most cells are microscopic in size.

Plants and animals consist of many small cells, and not one (or several) huge ones because:

● It is “beneficial” for cells to be small (the reason for this is covered in the previous paragraph).

● One or a few cells would not be enough to perform all the specific functions that underlie the life of such highly organized organisms as plants and animals. The higher the level of organization of a living organism, the more types of cells are included in its composition and the more pronounced cellular specialization is.

● In a multicellular organism, the cellular composition is constantly being renewed - cells die and are replaced by others. The death of one (or several) huge cells would lead to the death of the entire organism.

*Tasks marked with an asterisk require students to put forward various hypotheses. Therefore, when marking, the teacher should focus not only on the answer given here, but take into account each hypothesis, assessing the biological thinking of students, the logic of their reasoning, the originality of ideas, etc. After this, it is advisable to familiarize students with the answer given.

Dashkov M.L.

Cytology (“cytos” - cell, cell) is the science of cells. Modern cytology studies: the structure of cells, their formation as elementary living systems, studies the formation of individual cellular components, the processes of cell reproduction, reparation, adaptation to environmental conditions and other processes. In other words, modern cytology is the physiology of the cell.

The development of the study of the cell is closely connected with the invention of the microscope (from the Greek “micros” - small, “skopeo” - I look at). This is because the human eye is unable to distinguish objects smaller than 0.1 mm, which is 100 micrometers (abbreviated microns or µm). The sizes of cells (and even more so, intracellular structures) are significantly smaller.

For example, the diameter of an animal cell usually does not exceed 20 microns, a plant cell - 50 microns, and the length of the chloroplast of a flowering plant - no more than 10 microns. Using a light microscope, you can distinguish objects with a diameter of tenths of a micron.

The first microscope was designed in 1610 by Galileo and was a combination of lenses in a lead tube (Fig. 1.1). And before this discovery in 1590, the Dutch masters Jansens were engaged in glass production.

Rice. 1.1. Galileo Galilei (1564-1642)

The English physicist and naturalist R. Hooke was the first to use a microscope for research. (Fig. 1.2, 1.4). In 1665, he first described the cellular structure of cork and coined the term “cell.” (Fig. 1.3). R. Hooke made the first attempt to count the number of cells in a certain volume of a plug.

He formulated the idea of ​​a cell as a cell, completely closed on all sides, and established the fact of the cellular structure of plant tissues. These two main conclusions determined the direction of further research in this area.

Rice. 1.2. Robert Hooke (1635-1703)

Rice. 1.3. Cork cells studied by Robert Hooke

Rice. 1.4. Robert Hooke microscope

In 1674, the Dutch trader Antonio van Leeuwenhoek, using a microscope, first saw “animals” in a drop of water - moving living organisms (single-celled organisms, blood cells, sperm) and reported this to the scientific community (Fig. 1.5, 1.6). Descriptions of these “animalcus” earned the Dutchman worldwide fame and aroused interest in the study of the living microworld.

Rice. 1.5. Antonio van Leeuwenhoek (1632-1723)

Rice. 1.6. Microscope by Antonio van Leeuwenhoek

In 1693, during Peter I’s stay in Delphi, A. Leeuwenhoek demonstrated to him how blood moves in the fin of a fish. These demonstrations made such a great impression on Peter I that upon returning to Russia, he created a workshop of optical instruments. In 1725, the St. Petersburg Academy of Sciences was organized.

Talented masters I.E. Belyaev, I.P. Kulibin made microscopes (Fig. 1.7, 1.8, 1.9), in the design of which academicians L. Euler and F. Epinus took part.

Rice. 1.7. I.P. Kulibin (1735-1818)

Rice. 1.8. I.E. Belyaev

Rice. 1.9. Microscopes made by Russian craftsmen

In 1671–1679 Italian biologist and physician Marcello Malpighi gave the first systematic description of the microstructure of plant organs, which laid the foundation for plant anatomy (Fig. 1.10).

Rice. 1.10. Marcello Malpighi (1628-1694)

In 1671–1682 the Englishman Nehemiah Grew described in detail the microstructures of plants; introduced the term “tissue” to refer to the concept of a collection of “bubbles” or “bags” (Fig. 1.11). Both of these researchers (they worked independently of each other) gave amazingly accurate descriptions and drawings. They came to the same conclusion regarding the universality of the construction of plant tissue from vesicles.

Rice. 1.11. Nehemiah Grew (1641-1712)

In the 20s of the XIX century. The most significant works in the field of studying plant and animal tissues belong to the French scientists Henri Dutrochet (1824), Francois Raspail (1827), and Pierre Turpin (1829). They proved that cells (sacs, vesicles) are the elementary structures of all plant and animal tissues. These studies paved the way for the discovery of the cell theory.

One of the founders of embryology and comparative anatomy, academician of the St. Petersburg Academy of Sciences Karl Maksimovich Baer showed that the cell is a unit of not only the structure, but also the development of organisms (Fig. 1.12).

Rice. 1.12. K.M. Baer (1792-1876)

In 1759, the German anatomist and physiologist Caspar Friedrich Wolf proved that the cell is a unit of growth (Fig. 1.13).

Rice. 1.13. K.F. Wolf (1733–1794)

1830s Czech physiologist and anatomist J.E. Purkyne (Fig. 1.14), German biologist I.P. Muller proved that cellular organization is universal for all types of tissues.

Rice. 1.14. Ya.E. Purkyne (1787-1869)

In 1833, British botanist R. Brown (Fig. 1.15) described the nucleus of a plant cell.

Rice. 1.15. Robert Brown (1773-1858)

In 1837 Matthias Jakob Schleiden (Fig. 1.16) proposed a new theory of the formation of plant cells, recognizing the decisive role of the cell nucleus in this process. In 1842 he first discovered nucleoli in the nucleus.

According to modern ideas, Schleiden's specific studies contained a number of errors: in particular, Schleiden believed that cells could arise from structureless matter, and the plant embryo could develop from a pollen tube (the hypothesis of the spontaneous generation of life).

Rice. 1.16. Matthias Jacob Schleiden (1804-1881)

German cytologist, histologist and physiologist Theodor Schwann (Fig. 1.17) became acquainted with the works of the German botanist M. Schleiden, who described the role of the nucleus in a plant cell. Comparing these works with his own observations, Schwann developed his own principles of cellular structure and development of living organisms.

In 1838, Schwann published three preliminary reports of the cellular theory, and in 1839, the work “Microscopic studies on the correspondence in the structure and growth of animals and plants,” where he published the basic principles of the theory of the cellular structure of living organisms.

F. Engels argued that the creation of cell theory was one of the three greatest discoveries in natural science of the 19th century, along with the law of energy transformation and evolutionary theory.

Rice. 1.17. Theodor Schwann (1810-1882)

In 1834–1847 Professor of the Medical-Surgical Academy in St. Petersburg P.F. Goryaninov (Fig. 1.18) formulated the principle according to which the cell is a universal model of organization of living beings.

Goryaninov divided the world of living beings into two kingdoms: the formless, or molecular, and organic, or cellular kingdom. He wrote that “...the organic world is, first of all, a cellular kingdom...”. He noted in his studies that all animals and plants consist of interconnected cells, which he called vesicles, that is, he expressed an opinion about the general structure of plants and animals.

Rice. 1.18. P.F. Goryaninov (1796-1865)

In the history of the development of cell theory, two stages can be distinguished:

1) the period of accumulation of observations on the structure of various unicellular and multicellular organisms of plants and animals (about 300 years);

2) the period of generalization of available data in 1838 and the formulation of the postulates of cell theory;