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Galactose (/ ɡ ə ˈ l æ k t oʊ s /, galacto-+ -ose, "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. [2] It is an aldohexose and a C-4 epimer of glucose. [3] A galactose molecule linked with a glucose molecule forms a lactose molecule.
Lactose, or milk sugar, is a disaccharide composed of galactose and glucose and has the molecular formula C 12 H 22 O 11.Lactose makes up around 2–8% of milk (by mass). The name comes from lact (gen. lactis), the Latin word for milk, plus the suffix -ose used to name sugars.
Many adult humans lack the lactase enzyme, which has the same function as β-galactosidase, so they are not able to properly digest dairy products. β-Galactose is used in such dairy products as yogurt, sour cream, and some cheeses which are treated with the enzyme to break down any lactose before human consumption. In recent years, β ...
Galactogen is a polysaccharide of galactose that functions as energy storage in pulmonate snails and some Caenogastropoda. [23] This polysaccharide is exclusive of the reproduction and is only found in the albumen gland from the female snail reproductive system and in the perivitelline fluid of eggs. [24]
Plant mannans have β(1-4) linkages, occasionally with α(1-6) galactose branches, forming galactomannans. They are insoluble and a form of storage polysaccharide. Ivory nut is a source of mannans. An additional type is galactoglucomannan found in soft wood with a mixed mannose/glucose β(1-4) backbone.
A segment of galactomannan showing mannose backbone (below) with a branching galactose unit (top) Galactomannans are polysaccharides consisting of a mannose backbone with galactose side groups, more specifically, a (1-4)-linked beta-D-mannopyranose backbone with branchpoints from their 6-positions linked to alpha-D-galactose, (i.e. 1-6-linked alpha-D-galactopyranose).
A galactoside is a glycoside containing galactose. The H of the OH group on carbon-1 of galactose is replaced by an organic moiety. [1] Structure of ONPG, an example of a β-galactoside. Depending on whether the glycosidic bond lies "above" or "below" the plane of the galactose molecule, galactosides are classified as α-galactosides or β ...
Galactokinase is an enzyme (phosphotransferase) that facilitates the phosphorylation of α-D-galactose to galactose 1-phosphate at the expense of one molecule of ATP. [1] Galactokinase catalyzes the second step of the Leloir pathway , a metabolic pathway found in most organisms for the catabolism of α-D-galactose to glucose 1-phosphate . [ 2 ]