galactose(redirected from galactose tolerance test)
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or milk sugar,
white crystalline disaccharide (see carbohydrate). It has the same empirical formula (C12H22O11) as sucrose (cane sugar) and maltose but differs from both in structure (see isomer).
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A monosaccharide and a constituent of oligosaccharides, notably lactose, melibiose, raffinose, and stachyose. It is also known as d -galactose and cerebrose (see illustration). Agar, gum arabic, mesquite gum, larch arabo galactan, and a variety of other gums and mucilages contain d -galactose. See Agar, Monosaccharide
l -Galactose (enantiomorph of d -galactose) occurs in several polysaccharides, including agar, flaxseed mucilage, snail galactogen, and chagual gum. Since d -galactose is usually also present, hydrolysis of these polysaccharides produces dl -galactose. See Carbohydrate
a monosaccharide; one of the most frequently encountered natural hexahydric alcohols, a hexose. It differs from glucose in the spatial position of the groups around the fourth carbon atom. Galactose is readily soluble in water and only slightly soluble in alcohol. It exists in aliphatic and cyclic (pyranose, or furanose) forms, which are in a state of tautomeric equilibrium:
In plant tissues galactose is a component of raffinose, melibiose, and stachyose, as well as polysaccharides — galactans, pectins, saponins, various gums and mucilages, gum arabic, and so on. In the animal and human body galactose is a component of lactose (milk sugar), galactogen, group-specific polysaccharides, cerebrosides, and muco-proteins. Galactose is part of many bacterial polysaccharides and can be fermented by so-called lactose yeast. In animal and plant tissues, galactose readily changes to glucose, which is more assimilated and can be converted to ascorbic and galacturonic acids.
L. L. KHACHATRIAN