Research Paper on Vitamin A
Vitamin
A is a group substances with a similar chemical structure, which includes retinoids: retinol (vitamin A1, akseroftol), degidroretinol (vitamin A2), retinal (retinitis, the aldehyde of vitamin A1), retinoic acid, and several pro-vitamins-carotenoids, among which the most important is ?- carotene. Retinoids are found in animal products, and carotenoids in plants. All these substances are readily soluble in nonpolar organic solvents (such as oils) and poorly soluble in water. They are deposited in the liver and can be accumulated in the tissues. Its overdose is toxic.
Vitamin was discovered in 1913. In 1931, it was described by its structure, and it was crystallized in 1937.
In humans and animals, Vitamin A has many biologically important functions. Retinal is a component of rhodopsin, the main visual pigment, which as well, in the form of retinoic acid, stimulates the growth and development. Retinol is a structural component of cell membranes and provides antioxidant protection.
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The lack of vitamin A produces various epithelial damage, deteriorating eyesight, broken wetting of the cornea. In addition, there is immune function decrease and growth retardation.
Substances of the group of vitamin A have crystalline form. They are insoluble in water but soluble in organic solvents.
Retinol decomposes when exposed to oxygen and is very sensitive to light. All compounds tend to cis-trans isomerization, particularly Relations 11 and 13, but other than 11-cis-retinal, all double bonds are trans-configuration.
The discovery of the vitamin A dates back to 1913, when two groups of scientists, Elmer McCollum (1859-1929) and Margaret Davies (1887-1967) from the University of Wisconsin and Thomas Osborne (1859-1929) and Lafayette Mendel (1872-1935) of Yale University, after a series of studies independently concluded that butter and yolk of an egg contains a necessary substance for normal functioning. In their experiments, it was shown that mice eat only a combination of casein, fat, lactose, starch, and salt were suffering from eye inflammation and diarrhea and died after about 60 days. When butter, cod liver oil or eggs have been added to the diet, their condition returned to normal. This meant that not only the presence of fat was required, but also some other substances. McCollum divided them into two classes – the fat-soluble factor A (actually contains vitamins A, E and D), and the water-soluble factor B.
In 1920, Jack Cecil Drummond (1891-1952) proposed a new range of vitamins and vitamin then acquired its present name. In the same year, Hopkins showed that vitamin A exposed to oxidation or strong heating was destroyed.
In 1931, Swiss chemist Paul Karrer (1889-1971) described the chemical structure of vitamin A. His achievement was awarded the Nobel Prize for Chemistry in 1937. Harry Holmes (1879-1958) and Ruth Corbet crystallized vitamin A in 1937. In 1946, David Adriaan van Dorp (1915-1995) and Josef Ferdinand Arens (1914-2001) synthesized vitamin A. Otto Isler (1920-1992) in 1947 developed an industrial method for its synthesis.
The role of vitamin A in vision was opened biochemist George Wald (1906-1997), for which he received the Nobel Prize in Physiology or Medicine in 1967.
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