Cell theory. Cell and cell theory According to one of the provisions of the cell theory

1) New cells are formed only from bacterial cells.
2) New cells are formed only as a result of the division of original cells.
3) New cells are formed from an old cell
4) New cells are formed by simple division in half.
A2. The ribosome contains
1) DNA 2) mRNA 3) r-RNA 4) t-RNA
A3. Lysosomes in cells are formed in
1) endoplasmic reticulum 2) mitochondria 3) cell center 4) Golgi complex
A4. Unlike chloroplasts, mitochondria
1) have a double membrane 2) have their own DNA 3) have grana 4) have cristae
A5. What function does the cell center perform in a cell?
1) takes part in cell division 2) is the custodian of hereditary information
3) is responsible for protein biosynthesis 4) is the center of template synthesis of ribosomal RNA
A6. What function do lysosomes perform in a cell?
1) break down biopolymers into monomers 2) oxidize glucose to carbon dioxide and water
3) carry out the synthesis of organic substances 4) carry out the synthesis of polysaccharides from glucose
A7. Prokaryotes are organisms that lack
1) cytoplasm 2) nucleus 3) membrane 4) DNA
A8. Organisms that do not need oxygen to live are called:
1) anaerobes 2) eukaryotes 3) aerobes 4) prokaryotes
A9. Complete oxygen breakdown of substances (3rd stage of energy metabolism) occurs in:
1) mitochondria 2) lysosomes 3) cytoplasm 4) chloroplasts
A10. A set of reactions for the biological synthesis of substances in a cell is
1) Dissimilation 2) Assimilation 3) Glycolysis 4) Metabolism
A11. Organisms, organic substances from the external environment, are called:
1) Heterotrophs 2) Saprophytes 3) Phototrophs 4) Autotrophs
A12. Photolysis of water occurs in the cell in
1) mitochondria 2) lysosomes 3) chloroplasts 4) endoplasmic reticulum
A13. During photosynthesis, oxygen is produced as a result of
1) photolysis of water 2) decomposition of carbon dioxide 3) decomposition of glucose 4) synthesis of ATP
A14. The primary structure of a protein molecule, determined by the nucleotide sequence of mRNA,
formed in the process
1) translation 2) transcription 3) reduplication 4) denaturation
A15. A section of DNA that encodes information about the sequence of amino acids in the primary
protein structure is called:
1) gene 2) triplet 3) nucleotide 4) chromosome
A16. The process of division of somatic cells with preservation of the diploid set of chromosomes is
1) Transcription 2) Translation 3) Reproduction 4) MitosisA17. Which triplet on DNA corresponds to the UGC codon on mRNA?
1) TGC 2) AGC 3) TCG 4) ACG
A18. The destruction of the nuclear envelope and the formation of the fission spindle occurs in
1) Anaphase 2) Telophase 3) Prophase 4) Prometaphase
A19. The duplication of all organelles occurs in
1) Anaphase 2) Telophase 3) Interphase 4) Metaphase
In tasks B1-B2, choose three correct answers from the six proposed. Write the answer in the form
sequences of numbers. 2 points for a correctly completed task
IN 1. From the proposed characteristics, select those that relate to mitochondria
1) Contains DNA 4) Regulates all processes of protein synthesis, metabolism and energy
2) Participate in protein synthesis 5) Synthesize organic substances from inorganic ones
3) Covered with two membranes 6) The inner membrane has projections - cristae
AT 2. Autotrophs versus heterotrophs
1) Synthesize organic substances 4) Use solar energy
2) Absorb organic substances from outside 5) Contain chloroplasts
3) Feed on dead organisms 6) Exist on living organisms

Answer

Animal, plant and bacterial cells have a similar structure. Later, these conclusions became the basis for proving the unity of organisms. T. Schwann and M. Schleiden introduced into science the fundamental concept of the cell: there is no life outside cells. The cell theory was supplemented and edited every time.

Provisions of the Schleiden-Schwann cell theory

1. All animals and plants are made up of cells.
2. Plants and animals grow and develop through the emergence of new cells.
3. A cell is the smallest unit of living things, and a whole organism is a collection of cells.

Basic provisions of modern cell theory

1. The cell is the elementary unit of life; outside the cell there is no life.
2. A cell is a single system; it includes many naturally interconnected elements, representing an integral formation consisting of conjugated functional units - organelles.
3. The cells of all organisms are homologous.
4. A cell comes into being only by dividing the mother cell, after doubling its genetic material.
5. A multicellular organism is a complex system of many cells united and integrated into systems of tissues and organs connected to each other.
6. The cells of multicellular organisms are totipotent.

Additional provisions of the cell theory

To bring the cell theory into more complete compliance with the data of modern cell biology, the list of its provisions is often supplemented and expanded. In many sources, these additional provisions differ; their set is quite arbitrary.

1. Prokaryotic and eukaryotic cells are systems of different levels of complexity and are not completely homologous to each other (see below).
2. The basis of cell division and reproduction of organisms is the copying of hereditary information - nucleic acid molecules (“each molecule of a molecule”). The concept of genetic continuity applies not only to the cell as a whole, but also to some of its smaller components - mitochondria, chloroplasts, genes and chromosomes.
3. A multicellular organism is a new system, a complex ensemble of many cells, united and integrated in a system of tissues and organs, connected to each other through chemical factors, humoral and nervous (molecular regulation).
4. Multicellular cells are totipotent, that is, they have the genetic potential of all cells of a given organism, are equivalent in genetic information, but differ from each other in the different expression (function) of various genes, which leads to their morphological and functional diversity - to differentiation.

Story

17th century

Link and Moldnhower established the presence of independent walls in plant cells. It turns out that the cell is a certain morphologically separate structure. In 1831, Mole proved that even seemingly non-cellular plant structures, such as aquifers, develop from cells.

Meyen in “Phytotomy” (1830) describes plant cells that “are either solitary, so that each cell is a special individual, as is found in algae and fungi, or, forming more highly organized plants, they are combined into more or less significant masses." Meyen emphasizes the independence of metabolism of each cell.

In 1831, Robert Brown describes the nucleus and suggests that it is a permanent component of the plant cell.

Purkinje School

In 1801, Vigia introduced the concept of animal tissue, but he isolated tissue based on anatomical dissection and did not use a microscope. The development of ideas about the microscopic structure of animal tissues is associated primarily with the research of Purkinje, who founded his school in Breslau.

Purkinje and his students (especially G. Valentin should be highlighted) revealed in the first and most general form the microscopic structure of the tissues and organs of mammals (including humans). Purkinje and Valentin compared individual plant cells with individual microscopic tissue structures of animals, which Purkinje most often called “grains” (for some animal structures his school used the term “cell”).

In 1837, Purkinje gave a series of talks in Prague. In them, he reported on his observations on the structure of the gastric glands, nervous system, etc. The table attached to his report gave clear images of some cells of animal tissues. Nevertheless, Purkinje was unable to establish the homology of plant cells and animal cells:

• firstly, by grains he understood either cells or cell nuclei;
• secondly, the term “cell” was then understood literally as “a space bounded by walls.”

Purkinje conducted the comparison of plant cells and animal “grains” in terms of analogy, and not homology of these structures (understanding the terms “analogy” and “homology” in the modern sense).

Müller's school and Schwann's work

The second school where the microscopic structure of animal tissues was studied was the laboratory of Johannes Müller in Berlin. Müller studied the microscopic structure of the dorsal string (notochord); his student Henle published a study on the intestinal epithelium, in which he described its various types and their cellular structure.

Theodor Schwann's classic research was carried out here, laying the foundation for the cell theory. Schwann's work was strongly influenced by the school of Purkinje and Henle. Schwann found the correct principle for comparing plant cells and elementary microscopic structures of animals. Schwann was able to establish homology and prove the correspondence in the structure and growth of the elementary microscopic structures of plants and animals.

The significance of the nucleus in a Schwann cell was prompted by the research of Matthias Schleiden, who published his work “Materials on Phytogenesis” in 1838. Therefore, Schleiden is often called the co-author of the cell theory. The basic idea of ​​cellular theory - the correspondence of plant cells and the elementary structures of animals - was alien to Schleiden. He formulated the theory of new cell formation from a structureless substance, according to which, first, a nucleolus condenses from the smallest granularity, and around it a nucleus is formed, which is the cell maker (cytoblast). However, this theory was based on incorrect facts.

In 1838, Schwann published 3 preliminary reports, and in 1839 his classic work “Microscopic studies on the correspondence in the structure and growth of animals and plants” appeared, the very title of which expresses the main idea of ​​cellular theory:

• In the first part of the book, he examines the structure of the notochord and cartilage, showing that their elementary structures - cells - develop in the same way. He further proves that the microscopic structures of other tissues and organs of the animal body are also cells, quite comparable to the cells of cartilage and notochord.
• The second part of the book compares plant cells and animal cells and shows their correspondence.
• In the third part, theoretical positions are developed and the principles of cell theory are formulated. It was Schwann's research that formalized the cell theory and proved (at the level of knowledge of that time) the unity of the elementary structure of animals and plants. Schwann's main mistake was the opinion he expressed, following Schleiden, about the possibility of the emergence of cells from structureless non-cellular matter.

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

Since the 1840s of the 19th century, 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 Remak. 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.

XX century

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 1930s, Soviet biologist O. B. Lepeshinskaya, based on her research data, put forward a “new cell theory” as opposed to “Vierchowianism.” 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, symplasts) and nuclear-free intercellular substance, which 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 parent cells, and the extracellular substance is the product of their secretion, that is, 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.

1a. All living organisms on Earth consist of cells similar in structure,

1b. ...chemical composition and functioning. This speaks of the common origin of all life on Earth.

1st century The cell is the basic unit:

• structural (organisms are made up of cells)
• functional (body functions are performed due to the work of cells)
• reproduction (reproduction occurs due to germ cells).

2a. All new cells are formed from existing cells through division.

2b. The growth and development of a multicellular organism occurs due to the growth and reproduction of one or more parent cells.

Guys

17th century:
Hook opened the cells on the cut of the cork.
Leeuwenhoek discovered single-celled organisms (spermatozoa, red blood cells, ciliates, bacteria)

19th century:
Brown discovered the nucleus in plant cells.
Schleiden found out that all plant cells have a nucleus, and concluded that all plants are built from cells similar in structure.
Schwann discovered the nucleus in animal cells, deduced the first cell theory (item 1a).
Virchow supplemented the cell theory (item 2a).

Tests

1. From the given formulations, indicate the position of the cell theory
A) Fertilization is the process of fusion of male and female gametes
B) Each new daughter cell is formed as a result of division of the mother cell
C) Allelic genes end up in different cells during mitosis
D) The development of an organism from the moment of fertilization of the egg until the death of the organism is called ontogenesis

2. The similarity of the structure and vital activity of cells of organisms from different kingdoms of living nature is one of the provisions
A) theories of evolution
B) cell theory
B) doctrine of ontogenesis
D) laws of heredity

3. Proof of the relationship of all plant species is
A) cellular structure of plant organisms
B) the presence of fossil remains
C) the extinction of some species and the formation of new ones
D) the relationship between plants and the environment

4) One of the provisions of the cell theory
A) when cells divide, chromosomes are capable of self-duplication
B) new cells are formed when the original cells divide
C) the cytoplasm of cells contains various organelles
D) cells are capable of growth and metabolism

5. According to the cell theory, the emergence of a new cell occurs through
A) metabolism
B) division of the original cell
B) reproduction of organisms
D) the relationship of all cell organelles

6. The cellular structure of organisms of all kingdoms of living nature, the similarity of the structure of cells and their chemical composition serve as evidence
A) the unity of the organic world
B) the unity of living and inanimate nature
B) evolution of the organic world
D) the origin of nuclear organisms from prenuclear ones

7. The unit of reproduction of organisms is
A) core
B) cytoplasm
B) cell
D) fabric

8. The unit of development of organisms is
A) core
B) chloroplasts
B) mitochondria
D) cell

9. What serves as proof of the relationship of plants and animals, the unity of their origin?
A) cellular structure
B) the presence of a variety of fabrics
C) the presence of organs and organ systems
D) the ability for vegetative reproduction

10. The cell contains hereditary information about the characteristics of the organism, which is why it is called
A) structural unit of living things
B) functional unit of living things
B) genetic unit of a living thing
D) unit of growth

11. Statement of the cell theory
A) chromosomes are capable of self-duplication
B) cells reproduce by division
C) there are organelles in the cytoplasm of the cell
D) cells are capable of mitosis and meiosis

12. According to cell theory, a cell is a unit
A) artificial selection
B) natural selection
B) the structure of organisms
D) body mutations

13. Cell theory generalizes ideas about
A) the diversity of the organic world
B) the similarity of the structure of all organisms
B) embryonic development of organisms
D) the unity of living and inanimate nature

14. “The cells of all organisms are similar in structure, chemical composition, and metabolism.” This position
A) hypotheses of the origin of life
B) cell theory
B) the law of homological series in hereditary variability
D) the law of independent distribution of genes

15. Which theory first confirmed the unity of the organic world
A) chromosomal
B) embryogenesis
B) evolutionary
D) cellular

16) Life processes in all organisms take place in a cell, so it is considered as a unit
A) reproduction
B) buildings
B) functional
D) genetic

17. Which formulation corresponds to the position of the cell theory
A) plant cells have a cell wall made of fiber
B) the cells of all organisms are similar in structure, chemical composition and vital activity
C) cells of prokaryotes and eukaryotes are similar in structure
D) cells of all tissues perform similar functions

18. Which of the following statements relates to the cell theory?
A) a zygote is formed during the process of fertilization, the fusion of male and female gametes
B) during the process of meiosis, four daughter cells with a haploid set of chromosomes are formed
C) cells are specialized in the functions they perform and form tissues, organs, organ systems
D) plant cells differ from animal cells in a number of ways

19. Organisms of plants, animals, fungi and bacteria consist of cells - this indicates

B) the diversity of structure of living organisms
B) connections between organisms and their environment
D) the complex structure of living organisms

20. Testifies to the unity of the organic world
A) cycle of substances
B) cellular structure of organisms
B) the relationship between organisms and the environment
D) adaptability of organisms to the environment

21. The cell is considered the unit of growth and development of organisms, since
A) it has a complex structure
B) the body consists of tissues
C) the number of cells increases in the body through mitosis
D) gametes are involved in sexual reproduction

22. The similarity in the structure and activity of cells of organisms from different kingdoms of living nature indicates
A) the unity of the organic world
B) the unity of living and inanimate nature
C) the relationships of organisms in nature
D) relationships between organisms and their habitat

23. Testifies to the unity of the organic world
A) the presence of a nucleus in the cells of living organisms
B) cellular structure of organisms of all kingdoms
C) the unification of organisms of all kingdoms into systematic groups
D) the diversity of organisms inhabiting the Earth

24. According to cell theory, the cells of all organisms
A) similar in chemical composition
B) identical in functions performed
B) have a nucleus and nucleolus
D) have the same organelles

25. German scientists M. Schleiden and T. Schwann, summarizing the ideas of different scientists, formulated
A) the law of germinal similarity
B) chromosomal theory of heredity
B) cell theory
D) law of homological series

26. The synthesis and breakdown of organic substances occurs in the cell, which is why it is called a unit
A) buildings
B) vital activity
B) growth
D) reproduction

27. Indicate one of the provisions of the cell theory
A) Sex cells always contain a haploid set of chromosomes
B) Each gamete contains one gene from each allele
C) Cells of all organisms have a diploid set of chromosomes
D) The smallest unit of structure, life activity and
development of organisms is a cell

28. According to what theory, organisms of different kingdoms have similar chemical compositions?
A) chromosomal
B) evolutionary
B) ontogeny
D) cellular

29. What indicates the relationship of organisms of all kingdoms
A) the presence of similar tissues
B) development from simple to complex
B) cellular structure
D) functional role in ecosystems

30. Which formulation corresponds to the position of the cell theory?
A) cells of all tissues perform similar functions
B) during the process of meiosis, four gametes with a haploid set of chromosomes are formed
C) animal cells do not have a cell wall
D) each cell arises as a result of the division of the mother cell

31. One of the statements of the cell theory is the following:
A) cell - the elementary unit of heredity
B) cell - unit of reproduction and development
C) all cells are different in their structure
D) all cells have different chemical compositions

32. Contributed to the development of cell theory
A) A.I. Oparin
B) V.I.Vernadsky
B) T. Schwann and M. Schleiden
D) G. Mendel

33. Due to the fact that nutrition, respiration, and the formation of waste products occur in any cell, it is considered a unit
A) growth and development
B) functional
B) genetic
D) body structure

34. The similarity of metabolism in the cells of organisms of all kingdoms of living nature is one of the manifestations of the theory
A) chromosomal
B) cellular
B) evolutionary
D) origin of life

35. Why is the cell considered the structural unit of living things?
A) metabolism occurs in it
B) cells are capable of dividing and growing
B) all cells have a similar chemical composition
D) organisms of all kingdoms of living nature consist of cells

36. A conclusion about the relationship of plants and animals can be made on the basis
A) chromosome theory
B) gene theory
B) the law of chained inheritance
D) cell theory

37. The similarity in the structure and functioning of the cells of all organisms indicates
A) relatedness of organisms
B) development of wildlife
B) adaptability of organisms
D) diversity of living nature

38. A cell is a unit of growth and development of an organism, since
A) it has a nucleus
B) it stores hereditary information
B) it is capable of division
D) tissues are made up of cells

39. Why has cell theory become one of the outstanding generalizations of biology?
A) revealed the mechanisms of the appearance of various types of mutations
B) explained the patterns of heredity and variability
B) established the relationship between ontogenesis and phylogeny
D) substantiated the unity of origin of all living things

40. An elementary biological system capable of self-reproduction and development -
A) core
B) organ
B) cell
D) fabric

41. According to what theory, organisms of different kingdoms have similar chemical compositions?
A) chromosomal
B) evolutionary
B) ontogeny
D) cellular

42. Unit of growth of organisms -
A) chromosome
B) fabric
B) organ
D) cell

43. Indicate one of the provisions of the cell theory
A) Somatic cells contain a diploid set of chromosomes
B) Gametes consist of one cell
B) A prokaryotic cell contains a ring chromosome
D) Cell - the smallest unit of structure and vital activity of organisms

44. Among the stated formulations, determine the position of the cell theory
A) Allelic genes during the process of meiosis end up in different germ cells
B) The cells of all organisms are similar in chemical composition and structure
B) Fertilization is the process of union of male and female cells
D) Ontogenesis is the development of an organism from the moment of fertilization of the egg until the death of the organism

45. A cell is an integral part of the tissues of multicellular plants, therefore it is considered a unit
A) development
B) growth
B) vital activity
D) buildings

Animal, plant and bacterial cells have a similar structure. Later, these conclusions became the basis for proving the unity of organisms. T. Schwann and M. Schleiden introduced into science the fundamental concept of the cell: there is no life outside cells. The cell theory was supplemented and edited every time.

Provisions of the Schleiden-Schwann cell theory

1. All animals and plants are made up of cells.
2. Plants and animals grow and develop through the emergence of new cells.
3. A cell is the smallest unit of living things, and a whole organism is a collection of cells.

Basic provisions of modern cell theory

1. The cell is the elementary unit of life; outside the cell there is no life.
2. A cell is a single system; it includes many naturally interconnected elements, representing an integral formation consisting of conjugated functional units - organelles.
3. The cells of all organisms are homologous.
4. A cell comes into being only by dividing the mother cell, after doubling its genetic material.
5. A multicellular organism is a complex system of many cells united and integrated into systems of tissues and organs connected to each other.
6. The cells of multicellular organisms are totipotent.

Additional provisions of the cell theory

To bring the cell theory into more complete compliance with the data of modern cell biology, the list of its provisions is often supplemented and expanded. In many sources, these additional provisions differ; their set is quite arbitrary.

1. Prokaryotic and eukaryotic cells are systems of different levels of complexity and are not completely homologous to each other (see below).
2. The basis of cell division and reproduction of organisms is the copying of hereditary information - nucleic acid molecules (“each molecule of a molecule”). The concept of genetic continuity applies not only to the cell as a whole, but also to some of its smaller components - mitochondria, chloroplasts, genes and chromosomes.
3. A multicellular organism is a new system, a complex ensemble of many cells, united and integrated in a system of tissues and organs, connected to each other through chemical factors, humoral and nervous (molecular regulation).
4. Multicellular cells are totipotent, that is, they have the genetic potential of all cells of a given organism, are equivalent in genetic information, but differ from each other in the different expression (function) of various genes, which leads to their morphological and functional diversity - to differentiation.

Story

17th century

Link and Moldnhower established the presence of independent walls in plant cells. It turns out that the cell is a certain morphologically separate structure. In 1831, Mole proved that even seemingly non-cellular plant structures, such as aquifers, develop from cells.

Meyen in “Phytotomy” (1830) describes plant cells that “are either solitary, so that each cell is a special individual, as is found in algae and fungi, or, forming more highly organized plants, they are combined into more or less significant masses." Meyen emphasizes the independence of metabolism of each cell.

In 1831, Robert Brown describes the nucleus and suggests that it is a permanent component of the plant cell.

Purkinje School

In 1801, Vigia introduced the concept of animal tissue, but he isolated tissue based on anatomical dissection and did not use a microscope. The development of ideas about the microscopic structure of animal tissues is associated primarily with the research of Purkinje, who founded his school in Breslau.

Purkinje and his students (especially G. Valentin should be highlighted) revealed in the first and most general form the microscopic structure of the tissues and organs of mammals (including humans). Purkinje and Valentin compared individual plant cells with individual microscopic tissue structures of animals, which Purkinje most often called “grains” (for some animal structures his school used the term “cell”).

In 1837, Purkinje gave a series of talks in Prague. In them, he reported on his observations on the structure of the gastric glands, nervous system, etc. The table attached to his report gave clear images of some cells of animal tissues. Nevertheless, Purkinje was unable to establish the homology of plant cells and animal cells:

• firstly, by grains he understood either cells or cell nuclei;
• secondly, the term “cell” was then understood literally as “a space bounded by walls.”

Purkinje conducted the comparison of plant cells and animal “grains” in terms of analogy, and not homology of these structures (understanding the terms “analogy” and “homology” in the modern sense).

Müller's school and Schwann's work

The second school where the microscopic structure of animal tissues was studied was the laboratory of Johannes Müller in Berlin. Müller studied the microscopic structure of the dorsal string (notochord); his student Henle published a study on the intestinal epithelium, in which he described its various types and their cellular structure.

Theodor Schwann's classic research was carried out here, laying the foundation for the cell theory. Schwann's work was strongly influenced by the school of Purkinje and Henle. Schwann found the correct principle for comparing plant cells and elementary microscopic structures of animals. Schwann was able to establish homology and prove the correspondence in the structure and growth of the elementary microscopic structures of plants and animals.

The significance of the nucleus in a Schwann cell was prompted by the research of Matthias Schleiden, who published his work “Materials on Phytogenesis” in 1838. Therefore, Schleiden is often called the co-author of the cell theory. The basic idea of ​​cellular theory - the correspondence of plant cells and the elementary structures of animals - was alien to Schleiden. He formulated the theory of new cell formation from a structureless substance, according to which, first, a nucleolus condenses from the smallest granularity, and around it a nucleus is formed, which is the cell maker (cytoblast). However, this theory was based on incorrect facts.

In 1838, Schwann published 3 preliminary reports, and in 1839 his classic work “Microscopic studies on the correspondence in the structure and growth of animals and plants” appeared, the very title of which expresses the main idea of ​​cellular theory:

• In the first part of the book, he examines the structure of the notochord and cartilage, showing that their elementary structures - cells - develop in the same way. He further proves that the microscopic structures of other tissues and organs of the animal body are also cells, quite comparable to the cells of cartilage and notochord.
• The second part of the book compares plant cells and animal cells and shows their correspondence.
• In the third part, theoretical positions are developed and the principles of cell theory are formulated. It was Schwann's research that formalized the cell theory and proved (at the level of knowledge of that time) the unity of the elementary structure of animals and plants. Schwann's main mistake was the opinion he expressed, following Schleiden, about the possibility of the emergence of cells from structureless non-cellular matter.

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

Since the 1840s of the 19th century, 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 Remak. 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.

XX century

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 1930s, Soviet biologist O. B. Lepeshinskaya, based on her research data, put forward a “new cell theory” as opposed to “Vierchowianism.” 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, symplasts) and nuclear-free intercellular substance, which 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 parent cells, and the extracellular substance is the product of their secretion, that is, 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.

Almost 400 years passed from the moment the cells were discovered until the modern position of the cell theory was formulated. The cell was first examined in 1665 by a naturalist from England. Having noticed cellular structures on a thin section of cork, he gave them the name cells.

With his primitive microscope, Hooke could not yet examine all the features, but as optical instruments improved and techniques for staining preparations emerged, scientists became increasingly immersed in the world of subtle cytological structures.

How did the cell theory come about?

A landmark discovery that influenced the further course of research and the current position of cell theory was made in the 30s of the 19th century. The Scotsman R. Brown, studying a plant leaf using a light microscope, discovered similar rounded compactions in plant cells, which he later called nuclei.

From this moment on, an important feature appeared for comparing the structural units of different organisms with each other, which became the basis for conclusions about the unity of the origin of living things. It is not for nothing that even the modern position of cell theory contains a reference to this conclusion.

The question of the origin of cells was raised in 1838 by the German botanist Matthias Schleiden. While massively studying plant material, he noted that in all living plant tissues the presence of nuclei is mandatory.

His compatriot zoologist Theodor Schwann made the same conclusions regarding animal tissues. After studying Schleiden's work and comparing many plant and animal cells, he came to the conclusion: despite their diversity, they all have a common feature - a formed nucleus.

Cell theory of Schwann and Schleiden

Having put together the available facts about the cell, T. Schwann and M. Schleiden put forward the main postulate. It was that all organisms (plants and animals) consist of cells that are similar in structure.

In 1858, another addition to cell theory was made. proved that the body grows by increasing the number of cells by dividing the original maternal ones. This seems obvious to us, but for those times his discovery was very advanced and modern.

At that time, the current position of Schwann’s cell theory in textbooks was formulated as follows:

1. All tissues of living organisms have a cellular structure.
2. Animal and plant cells are formed in the same way (cell division) and have a similar structure.
3. The body consists of groups of cells, each of them is capable of independent life.

Having become one of the most important discoveries of the 19th century, cell theory laid the foundation for the idea of ​​the unity of origin and commonality of evolutionary development of living organisms.

Further development of cytological knowledge

Improvement of research methods and equipment has allowed scientists to significantly deepen their knowledge of the structure and functioning of cells:

• the connection between the structure and function of both individual organelles and cells as a whole has been proven (specialization of cytostructures);
• each cell individually demonstrates all the properties inherent in living organisms (grows, reproduces, exchanges matter and energy with the environment, is mobile to one degree or another, adapts to changes, etc.);
• organelles cannot individually exhibit such properties;
• animals, fungi, and plants have organelles that are identical in structure and function;
• All cells in the body are interconnected and work harmoniously, performing complex tasks.

Thanks to new discoveries, the provisions of the theory of Schwann and Schleiden were refined and supplemented. The modern scientific world uses the expanded postulates of the fundamental theory in biology.

In the literature you can find a different number of postulates of modern cell theory; the most complete version contains five points:

1. The cell is the smallest (elementary) living system, the basis for the structure, reproduction, development and vital activity of organisms. Non-cellular structures cannot be called living.
2. Cells appear solely by dividing existing ones.
3. The chemical composition and structure of the structural units of all living organisms are similar.
4. A multicellular organism develops and grows through the division of one/several original cells.
5. The similar cellular structure of the organisms inhabiting the Earth indicates a single source of their origin.

The original and modern provisions of the cell theory have many similarities. In-depth and expanded postulates reflect the current level of knowledge on the structure, life and interaction of cells.