Vitamin A is a group of unsaturated nutritional organic compounds, that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids, and beta-carotene. A group of unsaturated nutritional organic compounds and several provitamin A carotenoids, and beta-carotene.
Vitamin A is a group of unsaturated nutritional organic compounds, that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids, and beta-carotene. Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system and good vision. Vitamin A can be found in two principal forms in foods 1  : Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. 2  Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester. n. A fat-soluble vitamin or a mixture of vitamins, especially vitamin A 1 or a mixture of vitamins A 1 and A 2, occurring principally in fish-liver oils, milk, and some yellow and dark green vegetables, and functioning in normal cell growth and development. A vitamin important for normal vision, tissue growth, and healthy skin. It is found in fish-liver oils, milk, green leafy vegetables, and yellow vegetables and fruits. 1 Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. A form of vitamin A called retinal is responsible for transmitting light sensation in the retina of the eye. Deficiency of vitamin A leads to night blindness. The word vitamin was coined in 1911 by the Warsaw-born biochemist Casimir Funk (1884-1967). In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to retinol (chemically an alcohol) in the small intestine. The retinol form functions as a storage form of the vitamin, and can be converted to and from its visually active aldehyde form, retinal. Vitamin A can be found in two principal forms in foods 1  : Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. 2  Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester. Definition of VITAMIN A. : any of several fat-soluble vitamins (as retinol) found especially in animal products (as egg yolk, milk, or fish-liver oils) or a mixture of them whose lack in the animal body causes epithelial tissues to become keratinous (as in the eye with resulting visual defects). See vitamin A defined for kids. ADVERTISEMENT. Noun. 1. vitamin A-any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes. antiophthalmic factor, axerophthol, A. fat-soluble vitamin-any vitamin that is soluble in fats. A vitamin important for normal vision, tissue growth, and healthy skin. It is found in fish-liver oils, milk, green leafy vegetables, and yellow vegetables and fruits. Vitamin A: Vitamin A is retinol. Carotene compounds (found, for example, in egg yolk, butter and cream) are gradually converted by the body to vitamin A (retinol). A form of vitamin A called retinal is responsible for transmitting light sensation in the retina of the eye. Deficiency of vitamin A leads to night blindness. The word vitamin was coined in 1911 by the Warsaw-born biochemist Casimir Funk (1884-1967). 1 Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. 2  Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester. 3  It is also commercially produced and administered as esters such as retinyl acetate or palmitate. Vitamin A can be found in two principal forms in foods 1  : Vitamin C: An essential nutrient found mainly in fruits and vegetables. The body requires vitamin C to form and maintain bones, blood vessels, and skin. Vitamin C is also known as ascorbic acid. Vitamin C is a water-soluble vitamin, one that cannot be stored by the body except in insignificant amounts. It must be replenished daily.  vitamin A. n. 1. (Elements & Compounds) a fat-soluble yellow unsaturated alcohol occurring in green and yellow vegetables (esp carrots), butter, egg yolk, and fish-liver oil (esp halibut oil). It is essential for the prevention of night blindness and the protection of epithelial tissue. Formula: C20H30O. A vitamin important for normal vision, tissue growth, and healthy skin. It is found in fish-liver oils, milk, green leafy vegetables, and yellow vegetables and fruits.
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definition of vitamin a