Who saw the cells for the first time? The animal cell is the history of knowledge. History of cell discovery

Cell theory or cellular doctrine states that all organisms are composed of similar organized units called cells. The idea was formally formulated in 1839 by Schleiden and Schwann and is the basis of modern biology. This idea was preceded by other biological paradigms, such as Darwin's Theory of Evolution (1859), Mendel's Theory of Heredity (1865), and the creation of comparative biochemistry (1940).

The first cells discovered in the cortex

While the invention of the telescope opened up the boundless cosmos to mankind, the creation of the microscope revealed a smaller world, demonstrating what living organisms are made of. In 1665, Robert Hooke first saw and named a cell. He noted that it looked like a cell or small space. However, Hooke was actually examining the dead cell walls of a plant (bark) under a microscope. The first person to witness the existence of living cells under a microscope was Antonie van Leeuwenhoek, who described the spirogyra algae in 1674. Then van Leeuwenhoek may also have seen the bacterium.

Formation of cell theory

In 1838, Theodor Schwann and Matthias Schleiden were enjoying afternoon coffee while talking about cell research. It is believed that Schwann, having heard Schleiden's description of plant cells with a nucleus, was simply amazed by the similarity of these plant cells with the cells that he discovered in animal tissues. Both scientists immediately headed to Schwann's laboratory to look at his samples. The following year, Schwann published a book on animal and plant cells (Schwann 1839), but this treatise did not name others who contributed to this knowledge, including Schleiden (1838). He summarized his observations in three conclusions about cells:

• The cell is the unit of structure, physiology and organization of living organisms.
• the cell maintains a dual existence as a separate element and building material in the organization of organisms.
• the cell is formed by the formation of a free cell, similar to the formation of crystals (spontaneous generation).

Today we know that the first two theses are correct, but the third is completely wrong. The correct interpretation of the formation of cells by division was eventually formulated by other scientists and formally proclaimed in the famous dictum of Rudolf Virchow: “All cells arise only from pre-existing cells.”

Modern cell theory

• All known living things are made of cells.
• The cell is the structural and functional unit of all living organisms.
• All cells are formed from pre-existing cells by division (there is no spontaneous generation).
• Cells contain hereditary information that is passed from cell to cell as they divide.
• All cells are identical in chemical composition.
• The entire flow of life energy (metabolism and biochemistry) occurs inside cells.

Due to the rapid development of molecular biology in the 20th century, many studies in cytology took place in the 1950s. It has become possible to maintain, grow and manipulate cells outside of living organisms. The first permanent cell line outside a living organism was obtained in 1951 by George Otto Gay and colleagues: this cell line was taken from a cervical tumor of Henrietta Lacks, who died of cancer in 1951. The cell line, which was eventually named HeLa, marked a watershed in the study of cell biology. The structure of DNA was a significant breakthrough in molecular biology.

Major advances in cell research in the subsequent decade included the characterization of the minimum requirements for cell hosts and the development of sterile cell culture techniques. This was also facilitated by earlier improvements in electron microscopy and more recent advances such as the development of transfection techniques, the discovery of green fluorescent protein in jellyfish, and the discovery of small interfering RNAs among other RNAs.

Chronology of events

1595 – Jansen invents the first compound microscope.

1655 – Hooke describes the cortex cell.

1674 – Leeuwenhoek discovers the simplest cells. Nine years later, he discovers the bacterium.

1833 – Brown describes the cell nucleus in an orchid cell.

1838 – Schleiden and Schwann propose their cell theory.

1840 – Albrecht von Rolliker realizes that sperm and eggs are also cells.

1856 – N. Pringsheim studies how sperm penetrates the egg.

1858 – Rudolf Virchow (physician, pathologist and anthropologist) utters his famous phrase “omnis cellula e cellula”, which means that each cell can only be formed from an already existing cell.

1857 – Kolliker describes mitochondria.

1879 – Flemming describes the behavior of chromosomes during mitosis.

1883 – Cells are haploid, theory of chromosomal inheritance.

1898 – Golgi describes the Golgi apparatus.

1938 – Behrens uses differential centrifugation to separate the nucleus from the cytoplasm.

1939 – Siemens produces the first commercial transmission electron microscope.

1952 – Gay and colleagues obtain the first permanent human cell line.

1955 – Eagle determines the nutritional requirements of animal cells in culture.

1957 – Meselson, Stahl and Winograd develop cesium chloride density gradient centrifugation for the separation of nucleic acids.

1965 – Ham introduces serum-free vehicle. Cambridge Instruments produces the first commercial scanning electron microscope.

1976 – Sato and colleagues publish papers showing that different cell lines require different compositions of hormones and different growth factors in a serum environment.

1981 – The first transgenic mice and fruit flies are grown. The first mouse embryonic stem cell line was obtained.

1995 – Tsien identifies a GFP mutant with enhanced spectral properties.

1998 – A mouse is cloned from somatic cells.

1999 – Hamilton and Balcomb discover small interfering RNAs as a post-transcriptional silencing of gene expression in plants.

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 Jacob 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;

The vast majority of cells are microscopically small and cannot be seen with the naked eye. It became possible to see a cell and begin to study it only when the microscope was invented. The first microscopes appeared at the beginning of the 17th century. The microscope was first used for scientific research by the English scientist Robert Hooke (1665). Examining thin sections of cork under a microscope, he saw numerous small cells on them. Hooke called these cells, separated from each other by dense walls, cells, using the term “cell” for the first time.

In the subsequent period, which covered the second half of the 17th century, the entire 18th century. and the beginning of the 19th century. The microscope was being improved and data on animal and plant cells was accumulating. By the middle of the 19th century, the microscope had been significantly improved and much had become known about the cellular structure of plants and animals. The main materials about the cellular structure of plants at this time were collected and summarized by the German botanist M. Schleiden.

All the data obtained about the cell served as the basis for the creation of the cellular theory of the structure of organisms, which was formulated in 1838 by the German zoologist T. Schwann. Studying the cells of animals and plants, Schwann discovered that they were similar in structure, and established that the cell is a common elementary unit of structure of animal and plant organisms. Schwann outlined the theory of the cellular structure of organisms in his classic work “Microscopic studies on the correspondence in the structure and growth of animals and plants.”

At the beginning of the last century, the famous scientist, academician of the Russian Academy of Sciences Karl Baer discovered the mammalian egg and showed that all organisms begin their development from one cell. This cell is a fertilized egg, which splits, forms new cells, and from them the tissues and organs of the future organism are formed.

Baer's discovery complemented the cell theory and showed that the cell is not only a unit of structure, but also a unit of development of all living organisms.

An extremely significant addition to cell theory was the discovery of cell division. After the discovery of the process of cell division, it became quite obvious that new cells are formed by dividing existing ones, and do not arise anew from non-cellular matter.

The theory of the cellular structure of organisms also includes the most important materials for proving the unity of the origin, structure and development of the entire organic world. F. Engels highly appreciated the creation of the cell theory, placing it in importance next to the law of conservation of energy and the theory of natural selection of Charles Darwin.

By the end of the 19th century. The microscope was improved so much that it became possible to study the details of the cell structure and its main structural components were discovered. At the same time, knowledge began to accumulate about their functions in the life of the cell. The emergence of cytology, which currently represents one of the most intensively developing biological disciplines, dates back to this time.

Major events associated with the early development of cell biology include:

• 1665 - Robert Hooke first saw dead cells while studying the structure of a cork under a microscope. Hooke believed that cells were empty and that cell walls were living matter.
• 1650-1700 - Anthony van Leeuwenhoek first observed living cells under a microscope, in particular protozoa, as well as red blood cells.
• 1831-1839 - Robert Brown described the nucleus as a spherical body found in plant cells.
• 1838-1839 - botanist Matthias Schleiden and zoologist Theodor Schwann, combining the ideas of different scientists, created the cellular theory, according to which the cell is the basic structural and functional unit of living organisms.
• 1840 - Purkinje proposed the name protoplasm to denote the cellular contents, making sure that it was the contents, and not the cell walls, that were living matter.
• 1855 - Virchow proved that all cells are formed from other cells by division.
• 1866 - Haeckel established that the preservation and transmission of hereditary characteristics is carried out by the nucleus.
• 1866-1898 - describes the main components of a cell that can be seen under an optical microscope. Cytology takes on the character of an experimental science.
• 1900 - with the advent of genetics, cytogenetics begins to develop, studying the behavior of chromosomes during division and fertilization, its influence on the hereditary characteristics of organisms.
• 1946 - the use of the electron microscope began in biology, which made it possible to study the ultrastructures of cells.

– 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 cork, 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.

Question 1. Tell us about the history of the discovery of the cell.
The discovery of the cellular structure of living organisms became possible thanks to the advent of the microscope. Its prototype was invented in 1590 by the Dutch glass grinder Zachary Jansen. It is known about the first microscope that it consisted of a tube attached to a stand and had two magnifying glasses.
The importance of the microscope for studying the structure of sections of plant and animal objects was first appreciated by the English physicist and botanist Robert Hooke. In 1665, on sections of cork, he discovered structures resembling a honeycomb, and called them cells or cells. However, Hooke was mistaken in believing that cells are empty, and living matter is cell walls.
Dutch naturalist Antonie van Leeuwenhoek in the second half of the 17th century. improved the microscope and was the first to see living cells. He observed and sketched a number of protozoa, sperm, bacteria, red blood cells, and even their movement in capillaries.

Question 2. Who and when was the cell theory first formulated?
The study of plant and animal cells made it possible to generalize all the features of their structure. In 1838, M. Schleiden created the theory of cytogenesis (cell formation). His main merit is raising the question of the origin of cells in the body. In 1839, T. Schwann, based on the works of M. Schleiden, created the cell theory. Basic principles of cell theory (M. Schleiden and T. Schwann):
1) all tissues consist of cells;
2) plant and animal cells have common structural principles, because arise in the same ways;
3) each individual cell is independent, and the activity of the body is the sum of the vital activity of individual cells.
R. Virchow also paid great attention to the further development of cell theory in 1858. He not only brought together all the numerous disparate facts, but also convincingly showed that cells are a permanent structure and arise only through the reproduction of their own kind - “every cell comes from another cell as a result of division, just as a plant is formed from a plant, and from animals animals”, i.e. discovered cell division.

Question 3. List the modern provisions of cell theory.
Nowadays, cytology, using the achievements of genetics, molecular and physicochemical biology, is developing very quickly. And although the basic principles of the theory of T. Schwann and M. Schleiden remain relevant, the data obtained made it possible to form deeper ideas about the structure and functions of the cell. On their basis, modern cell theory was formulated. Let us list its main provisions:
1) cell is a unit of structure, functioning, reproduction and development of living organisms;
2) the cells of all organisms are similar in structure and chemical composition;
3) cell reproduction occurs by dividing the mother cell;
4) the cells of multicellular organisms are specialized: they perform different functions and form tissues.

Question 4. Describe the significance of cell theory for the development of biology.
According to philosophers who studied the history of science (for example, Friedrich Engels), cell theory is one of the greatest discoveries of the 19th century. She played a huge role in the development of not only biology, but also natural science in general. Protozoa, bacteria, many fungi and algae are cells that exist separately from each other. The body of all multicellular organisms - plants, fungi and animals - is built from a greater or lesser number of cells, which are the elementary structures that make up a complex organism. Regardless of whether a cell is an integral living system or part of it, it has a set of characteristics and properties common to all cells.
Cell theory for the first time unambiguously indicated the unity of the living world. With its appearance, the gap between the animal kingdom and the plant kingdom disappeared. Based on cell theory in the mid-19th century. Cytology arose - a science that studies the structure and functions of cells.
Think about for which representatives of the organic world the concepts of “cell” and “organism” coincide.
A cell is the basic structural, functional and genetic unit of organization of living things, an elementary living system. A cell can exist as a separate organism.
The concepts of “cell” and “organism” coincide when we are talking about single-celled organisms. These include prokaryotes, or non-nuclear ones (in particular, bacteria), and eukaryotes, or nuclear ones, include protozoa (such as the ciliate slipper, Chlamydomonas, green euglena). Their body consists of one cell, which implements all the functions of the body - metabolism, irritability, reproduction, movement. These functions are facilitated by a variety of organelles, including those for special purposes (for example, flagella and cilia provide movement). Single-celled organisms are often able to form clusters - colonies. However, the concept of “multicellular organism” is not yet applicable to a colony, since the cells that make up it have the same type of structure (they are not divided into tissues), weakly interact with each other and, being isolated from the colony, continue to exist and reproduce independently without any problems.