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a yellow or red pigment found in many dark green, leafy, and yellow vegetables such as collards, turnips, carrots, sweet potatoes, and squash, as well as in yellow fruit, milk, egg yolk, and body fat; it is a chromolipoid hydrocarbon existing in four forms (α-, β-, γ-, and δ-carotene), which can be converted into vitamin A in the body.
1. the β isomer of carotene.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
A member of a class of carotenoids, yellow-red pigments (lipochromes) widely distributed in plants and animals, notably in carrots, and closely related in structure to the xanthophylls and lycopenes and to the open-chain squalene; of particular interest in that they include precursors of the vitamins A (provitamin A carotenoids). Chemically, they consist of 8 isoprene units in a symmetric chain with the 2 isoprenes at each end cyclized, forming either α-carotene or β-carotene (γ-carotene has only one end cyclized). The cyclic ends of β-carotene are identical β-ioninelike structures; thus, on oxidative fission, β-carotene yields 2 molecules of vitamin A. The cyclic ends of α-carotene differ in that one is an α-ionone and the other a β-ionone; on fission, α-carotene, like γ-carotene, yields 1 molecule of vitamin A (a β-ionone derivative).
Farlex Partner Medical Dictionary © Farlex 2012
An orange-yellow to red crystalline pigment, C40H56, found in animal tissue and certain plants, such as carrots and squash. It exists in several isomeric forms and is converted to vitamin A in the liver.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
Yellow-red pigments (lipochromes) widely distributed in plants and animals, notably in carrots, and closely related in structure to the xanthophylls and lycopenes and to the open-chain squalene; they include precursors of vitamin A (provitamin A carotenoids).
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
caroteneOne of a group of orange pigments found in carrots and some other vegetables. Beta-carotene (provitamin A) is converted to vitamin A in the liver. This vitamin is needed for normal growth and development of bone and skin, for the development of the fetus and for the proper functioning of the RETINA.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
carotenean orange plant pigment of the CAROTENOID group which is usually present in the CHLOROPLASTS, and sometimes occurs in pigment-containing structures called CHROMOPLASTS which are found in yellow/orange leaves, vegetables and fruits. Carotene is also found in green leaves but the colour is masked; the orange colour can be seen in autumn leaves as the chlorophylls break down first. Carotene is necessary for the production of vitamin A in man and has an ABSORPTION SPECTRUM of about 450 nm. Carotene acts as an accessory pigment, passing energy to chlorophyll a for use in LIGHT REACTIONS and protecting chlorophyll from excessive light, and from oxidation by the oxygen produced in PHOTOSYNTHESIS.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
Yellow-red pigments widely distributed in plants and animals, notably in carrots; include precursors of vitamin A.
Medical Dictionary for the Dental Professions © Farlex 2012