All Cells Come From Existing

Biology of cells

Human cancer cells with nuclei (specifically the DNA) stained blueish. The cardinal and rightmost prison cell are in interphase, so the unabridged nuclei are labeled. The cell on the left is going through mitosis and its Dna has condensed.

In biological science, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are fabricated upwards of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come up from pre-existing cells. Cells are the bones unit of construction in all organisms and as well the basic unit of measurement of reproduction.

The 3 tenets of the cell theory are:

1. All living organisms are equanimous of one or more cells.
2. The cell is the basic unit of structure and organization in organisms.
3. Cells arise from pre-existing cells.

The theory was in one case universally accepted, but at present some biologists consider non-cellular entities such equally viruses living organisms,^[ane] and thus disagree with the first tenet. As of 2021: "expert opinion remains divided roughly a third each between yes, no and don't know".^[2] As in that location is no universally accepted definition of life, word will continue.

History

With continual improvements made to microscopes over time, magnification technology advanced plenty to discover cells. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, known as cell biology. When observing a piece of cork under the scope he was able to encounter pores. This was shocking at the time because information technology was believed no one else had seen these. To further support his theory, Matthias Schleiden and Theodor Schwann both studied cells of both animal and plants. What they discovered was there were significant differences between the two types of cells. This put forth the idea that cells were not but fundamental to plants, but animals also.^[three]

Microscopes

A reproduction of Anton van Leeuwenhoek's microscope from the 17th century with a magnification of 300x^[4]

Robert Hooke's microscope

Robert Hooke's microscope was a recreation of Anton van Leeuwenhoek's microscope in the 17th century, except his was 300x magnification.^[4] The discovery of the jail cell was made possible through the invention of the microscope. In the showtime century BC, Romans were able to make glass. They discovered that objects appeared to be larger nether the glass. In Italy during the twelfth century, Salvino D'Armate made a piece of glass fit over one eye, allowing for a magnification event to that eye. The expanded use of lenses in eyeglasses in the 13th century probably led to wider spread employ of simple microscopes (magnifying spectacles) with limited magnification. Compound microscopes, which combine an objective lens with an eyepiece to view a existent epitome achieving much college magnification, first appeared in Europe around 1620. In 1665, Robert Hooke used a microscope about six inches long with two convex lenses inside and examined specimens under reflected light for the observations in his book Micrographia. Hooke besides used a simpler microscope with a single lens for examining specimens with straight transmitted light, because this allowed for a clearer image.^[5]

An extensive microscopic study was done by Anton van Leeuwenhoek, a draper who took the interest in microscopes after seeing one while on an apprenticeship in Amsterdam in 1648. At some point in his life before 1668, he was able to acquire how to grind lenses. This eventually led to Leeuwenhoek making his ain unique microscope. He made i with a single lens. He was able to use a single lens that was a pocket-sized glass sphere just allowed for a magnification of 270x. This was a large progression since the magnification before was only a maximum of 50x. After Leeuwenhoek, there was not much progress in microscope technology until the 1850s, ii hundred years after. Carl Zeiss, a German engineer who manufactured microscopes, began to make changes to the lenses used. But the optical quality did not improve until the 1880s when he hired Otto Schott and eventually Ernst Abbe.^[half-dozen]

Optical microscopes tin can focus on objects the size of a wavelength or larger, giving restrictions yet to advocacy in discoveries with objects smaller than the wavelengths of visible lite. The development of the electron microscope in the 1920s made it possible to view objects that are smaller than optical wavelengths, once more opening upward new possibilities in scientific discipline.^[6]

Discovery of cells

The cell was showtime discovered by Robert Hooke in 1665, which tin can be institute to exist described in his volume Micrographia. In this volume, he gave 60 'observations' in particular of various objects nether a coarse, compound microscope. One observation was from very thin slices of bottle cork. Hooke discovered a multitude of tiny pores that he named "cells". This came from the Latin word Cella, significant 'a modest room' similar monks lived in and as well Cellulae, which meant the six sided cell of a honeycomb. However, Hooke did non know their real construction or role. What Hooke had thought were cells, were actually empty cell walls of found tissues. With microscopes during this fourth dimension having a low magnification, Hooke was unable to meet that in that location were other internal components to the cells he was observing. Therefore, he did non call up the "cellulae" were alive. His cell observations gave no indication of the nucleus and other organelles establish in most living cells. In Micrographia, Hooke also observed mould, bluish in colour, constitute on leather. After studying information technology under his microscope, he was unable to notice "seeds" that would have indicated how the mould was multiplying in quantity. This led to Hooke suggesting that spontaneous generation, from either natural or artificial heat, was the cause. Since this was an sometime Aristotelian theory yet accepted at the time, others did non reject it and was not disproved until Leeuwenhoek later discovered that generation was accomplished otherwise.^[5]

Anton van Leeuwenhoek is another scientist who saw these cells soon afterwards Hooke did. He made employ of a microscope containing improved lenses that could magnify objects 270-fold. Under these microscopes, Leeuwenhoek found motile objects. In a letter of the alphabet to The Regal Society on October 9, 1676, he states that motion is a quality of life therefore these were living organisms. Over time, he wrote many more papers which described many specific forms of microorganisms. Leeuwenhoek named these "animalcules," which included protozoa and other unicellular organisms, like leaner. Though he did not take much formal education, he was able to identify the beginning authentic description of red blood cells and discovered bacteria after gaining interest in the sense of taste that resulted in Leeuwenhoek to observe the tongue of an ox, and then leading him to study "pepper water" in 1676. He also establish for the kickoff time the sperm cells of animals and humans. Once discovering these types of cells, Leeuwenhoek saw that the fertilization process requires the sperm prison cell to enter the egg prison cell. This put an end to the previous theory of spontaneous generation. After reading letters by Leeuwenhoek, Hooke was the first to ostend his observations that were idea to be unlikely by other contemporaries.^[5]

The cells in animate being tissues were observed after plants were because the tissues were so fragile and susceptible to tearing, it was difficult for such thin slices to exist prepared for studying. Biologists believed that there was a central unit to life, but were unsure what this was. It would not exist until over a hundred years later on that this fundamental unit was continued to cellular structure and existence of cells in animals or plants.^[7] This determination was not fabricated until Henri Dutrochet. Besides stating "the jail cell is the central element of organization",^[8] Dutrochet likewise claimed that cells were not but a structural unit of measurement, simply also a physiological unit of measurement.

In 1804, Karl Rudolphi and J. H. F. Link were awarded the prize for "solving the problem of the nature of cells", meaning they were the offset to prove that cells had contained jail cell walls by the Königliche Societät der Wissenschaft (Regal Society of Scientific discipline), Göttingen.^[9] Before, information technology had been thought that cells shared walls and the fluid passed between them this way.

Cell theory

Credit for developing cell theory is usually given to two scientists: Theodor Schwann and Matthias Jakob Schleiden.^[10] While Rudolf Virchow contributed to the theory, he is non as credited for his attributions toward information technology. In 1839, Schleiden suggested that every structural office of a plant was fabricated upwards of cells or the result of cells. He also suggested that cells were made by a crystallization process either within other cells or from the outside.^[11] However, this was not an original idea of Schleiden. He claimed this theory equally his ain, though Barthelemy Dumortier had stated information technology years before him. This crystallization process is no longer accepted with modern prison cell theory. In 1839, Theodor Schwann states that along with plants, animals are equanimous of cells or the product of cells in their structures.^[12] This was a major advancement in the field of biology since little was known about animal construction upwards to this bespeak compared to plants. From these conclusions nigh plants and animals, two of the iii tenets of cell theory were postulated.^[vii]

one. All living organisms are composed of one or more cells

2. The prison cell is the most basic unit of life

Schleiden'south theory of complimentary prison cell formation through crystallization was refuted in the 1850s past Robert Remak, Rudolf Virchow, and Albert Kolliker.^[6] In 1855, Rudolf Virchow added the third tenet to prison cell theory. In Latin, this tenet states Omnis cellula eastward cellula.^[7] This translated to:

3. All cells ascend only from pre-existing cells

Still, the idea that all cells come from pre-existing cells had in fact already been proposed by Robert Remak; it has been suggested that Virchow plagiarized Remak and did not give him credit.^[13] Remak published observations in 1852 on jail cell sectionalisation, claiming Schleiden and Schawnn were incorrect about generation schemes. He instead said that binary fission, which was get-go introduced by Dumortier, was how reproduction of new animal cells were made. In one case this tenet was added, the classical jail cell theory was complete.

Mod interpretation

The generally accustomed parts of modern prison cell theory include:

1. All known living things are made up of one or more cells^[14]
2. All living cells arise from pre-existing cells by partition.
3. The cell is the cardinal unit of construction and function in all living organisms.^[15]
4. The action of an organism depends on the full action of independent cells.^[sixteen]
5. Free energy flow (metabolism and biochemistry) occurs within cells.^[17]
6. Cells contain DNA which is establish specifically in the chromosome and RNA constitute in the cell nucleus and cytoplasm.^[xviii]
7. All cells are basically the same in chemical composition in organisms of similar species.^[17]

Mod version

The modern version of the cell theory includes the ideas that:

• Energy flow occurs inside cells.^[17]
• Heredity information (Deoxyribonucleic acid) is passed on from cell to cell.^[17]
• All cells have the same basic chemical limerick.^[17]

Opposing concepts in cell theory: history and background

The cell was offset discovered past Robert Hooke in 1665 using a microscope. The first cell theory is credited to the work of Theodor Schwann and Matthias Jakob Schleiden in the 1830s. In this theory the internal contents of cells were called protoplasm and described equally a jelly-similar substance, sometimes called living jelly. At virtually the same fourth dimension, colloidal chemistry began its development, and the concepts of bound water emerged. A colloid existence something between a solution and a suspension, where Brownian motion is sufficient to forbid sedimentation. The idea of a semipermeable membrane, a barrier that is permeable to solvent but impermeable to solute molecules was adult at about the aforementioned fourth dimension. The term osmosis originated in 1827 and its importance to physiological phenomena realized, but it wasn't until 1877, when the botanist Pfeffer proposed the membrane theory of jail cell physiology. In this view, the cell was seen to be enclosed by a thin surface, the plasma membrane, and cell water and solutes such as a potassium ion existed in a physical state similar that of a dilute solution. In 1889 Hamburger used hemolysis of erythrocytes to make up one's mind the permeability of various solutes. By measuring the time required for the cells to swell past their rubberband limit, the rate at which solutes entered the cells could exist estimated by the accompanying alter in jail cell volume. He also found that there was an apparent nonsolvent book of nigh 50% in red blood cells and afterwards showed that this includes water of hydration in add-on to the poly peptide and other nonsolvent components of the cells.

Evolution of the membrane and bulk stage theories

2 opposing concepts developed inside the context of studies on osmosis, permeability, and electrical properties of cells.^[xix] The offset held that these backdrop all belonged to the plasma membrane whereas the other predominant view was that the protoplasm was responsible for these properties. The membrane theory adult as a succession of ad-hoc additions and changes to the theory to overcome experimental hurdles. Overton (a afar cousin of Charles Darwin) outset proposed the concept of a lipid (oil) plasma membrane in 1899. The major weakness of the lipid membrane was the lack of an explanation of the high permeability to water, and then Nathansohn (1904) proposed the mosaic theory. In this view, the membrane is non a pure lipid layer, but a mosaic of areas with lipid and areas with semipermeable gel. Ruhland refined the mosaic theory to include pores to allow additional passage of minor molecules. Since membranes are more often than not less permeable to anions, Leonor Michaelis concluded that ions are adsorbed to the walls of the pores, changing the permeability of the pores to ions by electrostatic repulsion. Michaelis demonstrated the membrane potential (1926) and proposed that it was related to the distribution of ions across the membrane.^[20]

Harvey and Danielli (1939) proposed a lipid bilayer membrane covered on each side with a layer of protein to business relationship for measurements of surface tension. In 1941 Boyle and Conway showed that the membrane of frog muscle was permeable to both K ⁺
and Cl ⁻
, merely apparently non to Na ⁺
, so the idea of electric charges in the pores was unnecessary since a unmarried critical pore size would explain the permeability to Chiliad ⁺
, H ⁺
, and Cl ⁻
as well as the impermeability to Na ⁺
, Ca ⁺
, and Mg ²⁺
. Over the same time flow, information technology was shown (Procter and Wilson, 1916) that gels, which do non have a semipermeable membrane, would bang-up in dilute solutions.

Loeb (1920) also studied gelatin extensively, with and without a membrane, showing that more of the properties attributed to the plasma membrane could be duplicated in gels without a membrane. In particular, he found that an electrical potential departure between the gelatin and the exterior medium could exist developed, based on the H ⁺
concentration. Some criticisms of the membrane theory developed in the 1930s, based on observations such as the ability of some cells to swell and increase their surface surface area by a factor of k. A lipid layer cannot stretch to that extent without condign a patchwork (thereby losing its barrier properties). Such criticisms stimulated continued studies on protoplasm every bit the principal amanuensis determining cell permeability backdrop.

In 1938, Fischer and Suer proposed that water in the protoplasm is not gratuitous merely in a chemically combined form—the protoplasm represents a combination of protein, salt and water—and demonstrated the basic similarity between swelling in living tissues and the swelling of gelatin and fibrin gels. Dimitri Nasonov (1944) viewed proteins as the central components responsible for many properties of the cell, including electrical backdrop. By the 1940s, the bulk phase theories were not equally well developed as the membrane theories. In 1941, Brooks and Brooks published a monograph, "The Permeability of Living Cells", which rejects the bulk phase theories.

Emergence of the steady-state membrane pump concept

With the development of radioactive tracers, it was shown that cells are not impermeable to Na ⁺
. This was difficult to explain with the membrane barrier theory, and then the sodium pump was proposed to continually remove Na ⁺
as information technology permeates cells. This drove the concept that cells are in a country of dynamic equilibrium, constantly using energy to maintain ion gradients. In 1935, Karl Lohmann [de] discovered ATP and its function equally a source of free energy for cells, so the concept of a metabolically-driven sodium pump was proposed. The tremendous success of Hodgkin, Huxley, and Katz in the development of the membrane theory of cellular membrane potentials, with differential equations that modeled the phenomena correctly, provided fifty-fifty more support for the membrane pump hypothesis.

The mod view of the plasma membrane is of a fluid lipid bilayer that has protein components embedded within it. The structure of the membrane is now known in corking detail, including 3D models of many of the hundreds of different proteins that are jump to the membrane. These major developments in prison cell physiology placed the membrane theory in a position of dominance and stimulated the imagination of virtually physiologists, who now apparently accept the theory as fact—at that place are, however, a few dissenters.^{[ citation needed ]}

The reemergence of the bulk phase theories

In 1956, Afanasy S. Troshin published a book, The Problems of Jail cell Permeability, in Russian (1958 in High german, 1961 in Chinese, 1966 in English), in which he found that permeability was of secondary importance in determination of the patterns of equilibrium betwixt the jail cell and its environment. Troshin showed that cell water decreased in solutions of galactose or urea although these compounds did slowly permeate cells. Since the membrane theory requires an impermanent solute to sustain cell shrinkage, these experiments cast doubt on the theory. Others questioned whether the cell has enough energy to sustain the sodium/potassium pump. Such questions became even more urgent equally dozens of new metabolic pumps were added equally new chemical gradients were discovered.

In 1962, Gilbert Ling became the champion of the bulk phase theories and proposed his association-induction hypothesis of living cells.

Types of cells

Cells can be subdivided into the following subcategories:

1. Prokaryotes: Prokaryotes are relatively modest cells surrounded past the plasma membrane, with a feature cell wall that may differ in composition depending on the particular organism.^[21] Prokaryotes lack a nucleus (although they do have round or linear DNA) and other membrane-bound organelles (though they practice comprise ribosomes). The protoplasm of a prokaryote contains the chromosomal region that appears as fibrous deposits under the microscope, and the cytoplasm.^[21] Bacteria and Archaea are the ii domains of prokaryotes.
2. Eukaryotes: Eukaryotes are circuitous cells, which have over time acquired a mitochondrial symbiont and later developed a nucleus.^[22]

Animals have evolved a greater diversity of cell types in a multicellular trunk (100–150 dissimilar cell types), compared with 10–20 in plants, fungi, and protoctista.^[23]

Run across likewise

• Jail cell adhesion
• Cytoskeleton
• Prison cell biology
• Cellular differentiation
• Germ theory of disease
• Membrane models

References

1. ^ Villarreal, Luis P. (Baronial 8, 2008) Are Viruses Alive? Scientific American
2. ^ Farnsworth, Keith D. (2021). "An organisational systems-biology view of viruses explains why they are not live". Biosystems. 200: 104324. doi:10.1016/j.biosystems.2020.104324. ISSN 0303-2647. PMID 33307144. S2CID 228169048.
3. ^ National Geographic Society. (2019, May 22). "History of the Prison cell: Discovering the Cell". Retrieved November 05, 2020.
4. ^ ^{a b} "A glass-sphere microscope". Funsci.com. Archived from the original on 11 June 2010. Retrieved 13 June 2010.
5. ^ ^{a b c} Gest, H (2004). "The discovery of microorganisms by Robert Hooke and Antoni Van Leeuwenhoek, fellows of the Purple Society". Notes and Records of the Royal Society of London. 58 (2): 187–201. doi:10.1098/rsnr.2004.0055. PMID 15209075. S2CID 8297229.
6. ^ ^{a b c} Mazzarello, P. (1999). "A unifying concept: the history of cell theory". Nature Cell Biology. ane (1): E13–five. doi:10.1038/8964. PMID 10559875. S2CID 7338204. Archived from the original on 2015-06-03.
7. ^ ^{a b c} Robinson, Richard. "History of Biology: Jail cell Theory and Prison cell Structure". Advameg, Inc. Retrieved 17 March 2014.
8. ^ Dutrochet, Henri (1824) "Recherches anatomiques et physiologiques sur la structure intime des animaux et des vegetaux, et sur leur motilite, par M.H. Dutrochet, avec deux planches"
9. ^ Kalenderblatt Dezember 2013 – Mathematisch-Naturwissenschaftliche Fakultät – Universität Rostock. Mathnat.uni-rostock.de (2013-11-28). Retrieved on 2015-10-fifteen.
10. ^ Sharp, L. W. (1921). Introduction To Cytology. New York: McGraw Loma Book Company Inc.
11. ^ Schleiden, 1000. J. (1839). "Beiträge zur Phytogenesis". Archiv für Anatomie, Physiologie und wissenschaftliche Medicin. 1838: 137–176.
12. ^ Schwann, T. (1839). Mikroskopische Untersuchungen über dice Uebereinstimmung in der Struktur und dem Wachsthum der Thiere und Pflanzen. Berlin: Sander.
13. ^ Silver, GA (1987). "Virchow, the heroic model in medicine: health policy by award". American Periodical of Public Health. 77 (1): 82–viii. doi:10.2105/AJPH.77.i.82. PMC1646803. PMID 3538915.
14. ^ Wolfe
15. ^ Wolfe, p. five
16. ^ Müller-Wille, Staffan (2010). "Cell theory, specificity, and reproduction, 1837–1870". Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences. 41 (3): 225–231. doi:10.1016/j.shpsc.2010.07.008. ISSN 1369-8486. PMC4353839. PMID 20934643.
17. ^ ^{a b c d e} "The modern version of the Prison cell Theory". Retrieved 12 Feb 2015.
18. ^ Wolfe, p. 8
19. ^ Ling, Gilbert N. (1984). In search of the physical basis of life. New York: Plenum Press. ISBN0306414090.
20. ^ Michaelis, L. (1925). "Contribution to the Theory of Permeability of Membranes for Electrolytes". The Journal of Full general Physiology. 8 (2): 33–59. doi:ten.1085/jgp.8.2.33. PMC2140746. PMID 19872189.
21. ^ ^{a b} Wolfe, p. eleven
22. ^ Vellai, T; Vida, Yard (vii Baronial 1999). "The origin of eukaryotes: the deviation betwixt prokaryotic and eukaryotic cells". Proceedings of the Regal Club B: Biological Sciences. 266 (1428): 1571–1577. doi:10.1098/rspb.1999.0817. PMC1690172. PMID 10467746.
23. ^ Margulis, L. & Chapman, M.J. (2009). Kingdoms and Domains: An Illustrated Guide to the Phyla of Life on Earth ([4th ed.]. ed.). Amsterdam: Academic Press/Elsevier. p. 116.

Bibliography

• Wolfe, Stephen L. (1972). Biology of the prison cell. Wadsworth Pub. Co. ISBN978-0-534-00106-iii.

Further reading

• Turner West (January 1890). "The Cell Theory By and Present". J Anat Physiol. 24 (Pt 2): 253–87. PMC1328050. PMID 17231856.
• Tavassoli One thousand (1980). "The prison cell theory: a foundation to the building of biological science". Am. J. Pathol. 98 (one): 44. PMC1903404. PMID 6985772.

External links

• Mallery C (2008-02-11). "Cell Theory". Retrieved 2008-11-25 .
• "Studying Cells Tutorial". 2004. Retrieved 2008-xi-25 .

All Cells Come From Existing,

Source: https://en.wikipedia.org/wiki/Cell_theory

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