The cell theory or cell principle defines that all the living organisms are comprised of identical units of organization, termed as cells. A cell is the fundamental unit of a living organism. The concept of cell theory was officially stated in the year 1839 by Schleiden and Schwann and has remained as the base of modern biology. This unit defenses the fact that the idea of cell theory predates other big paradigms (that is, examples) of biology comprising Darwin's theory of evolution (in year 1859), Mendel's laws of inheritance (in the year, 1865) and the establishment of the comparative biochemistry (in the year, 1940).
First Cells Seen in Cork:
As the discovery of the telescope build up the Cosmos accessible to human inspection, the microscope exposed the identities of microbes and exhibits what living forms were comprised of. The cell was primary discovered and named by Robert Hooke in the year 1665. He stated that it looked strangely identical to cellular or small rooms that monks inhabited, therefore depriving the name. Though, what Hooke really saw was the dead cell walls of plant cells termed as the cork as it appeared beneath the microscope. Hooke's explanation of such walls was published in Micrographia. The cell walls viewed by Hooke gave no recognition of the nucleus and other organelles found in most of the living cells. The first man to observe a live cell under a microscope was Anton van Leeuwenhoek, who in year 1674 explained the alga spirogyra.
Formulation of the Cell Theory:
In year 1838, Matthias Schleiden and Theodor Schwann were enjoying after-dinner coffee and discussing concerning their studies on cells. It has been recommended that when Schwann heard Schleiden explain plant cells with nuclei, he was struck by resemblance of such plant cells to cells he had viewed in animal tissues. The two scientists went instantly to Schwann's lab to look at his slides. Schwann published his book on animal and plant cells in the year 1839. He summarized his explanations into three conclusions regarding cells:
1) The cell is the basic unit of structure, physiology and organization in the living things.
2) The cell maintains a dual existence as a separate entity and a building block in the construction of organisms.
3) Cells made by free-cell formation, identical to the formation of crystals (that is, spontaneous generation).
Modern Cell Theory:
Let us observe the given statements that symbolize the modern cell theory:
1) All known living things are building up of cells.
2) The cell is the structural functional unit of all the living things.
3) All cells occur from pre-existing cells through division. (Spontaneous Generation doesn't take place
4) Cells comprises of hereditary information that is passed from cell to cell throughout cell division
5) All cells are fundamentally the same in the chemical composition.
6) All energy flow (that is, metabolism and biochemistry) of life take place in cells.
As by the rapid growth of molecular biology in the mid 20th century, cell biology research exploded in the year 1950. It became probable to maintain, grow and manipulate the cells outside of living organisms. The first permanent definition to be so cultured was in the year 1951 by George Otto Gey and coworkers, derived from the cervical cancer cells taken from Henrietta Lacks, who died from the cancer in the year 1951. The cell line, that was ultimately termed to as HeLa cells, have been the division in studying cell biology merely as the structure of DNA was important breakthrough of the molecular biology.
In an avalanche of growth in the study of cells, the coming decade comprised the characterization of the minimal media needs for cells and growth of sterile cell culture methods. You must as well know that the study of cells was as well assisted by the previous advances in electron microscopy and later advances like the growth of transfection methods, discovery of small interfering RNA (siRNA), among the others.
1595: Jansen credited by first compound microscope.
1655: Hooke explained 'cells' in the cork.
1674: Leeuwenhoek invented protozoa. He observes bacteria some nine years later.
1833: Brown explained the cell nucleus in cells of the flower orchid.
1838: Schleiden and Schwann introduced cell theory.
1840: Albrecht von Roelliker understood that sperm cells and egg cells are as well cells.
1856: N. Pringsheim observed how a sperm cell penetrated the egg cell.
1858: Rudolf Virchow (physician, anthropologist and pathologist) illustrates his famous conclusion: omnis cellulae cellula, which is cells build up only from existing cells [that is, cells come from preexisting cells]
1857: Kolliker explained mitochondria.
1879: Fleming explained chromosome behavior throughout mitosis.
1883: Germ cells are haploid, chromosome theory of heredity.
1898: Golgi explained the Golgi apparatus.
1938: Behrens employed differential centrifugation to separate nuclei from the cytoplasm.
1939: Siemens generated the first commercial transmission electron microscope.
1952: Gey and coworkers set up a continuous human cell line.
1955: Eagle systematically stated the nutritional requires of animal cells in culture.
1957: Meselson, Stahl and Vinograd build up density gradient centrifugation in cesium chloride solutions for separating the nucleic acids.
1965: Ham proposed a defined serum-free medium. Cambridge Instruments generated the initial commercial scanning electron microscope.
1976: Sato and colleagues issue papers exhibiting that different cell lines need various mixtures of hormones and growth factors in the serum-free media.
1981: Transgenic mice and fruit flies are generated. Mouse embryonic stem cell line set up.
1995: Tsien recognizes mutant of GFP having enhanced spectral properties.
1998: Mice are cloned from the somatic cells.
1999: Hamilton and Baulcombe fin out siRNA as part of post-transcriptional gene silencing (PTGS) in the plants.
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