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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.
Galactogen is a polysaccharide of galactose that functions as energy storage in pulmonate snails and some Caenogastropoda. [1] 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.
Galactose-α-1,3-galactose, commonly known as alpha gal and the Galili antigen, is a carbohydrate found in most mammalian cell membranes. It is not found in catarrhines , [ 1 ] including humans, who have lost the GGTA1 gene.
Another nomenclature uses the systematic name of the molecular graph, a ' D-' or ' L-' prefix to indicate the position of the last chiral hydroxyl on the Fischer diagram (as above), and another italic prefix to indicate the positions of the remaining hydroxyls relative to the first one, read from bottom to top in the diagram, skipping the keto ...
However, where a terminal galactose unit is indicated, hydrolysis of GOS formed at an earlier stage in the process has occurred. The degree of polymerization of GOS can vary quite markedly, ranging from 2 to 8 monomeric units, depending mainly on the type of the enzyme used and the conversion degree of lactose.
In metabolism, the β-glycosidic bond in D-lactose is hydrolyzed to form D-galactose and D-glucose, which can be absorbed through the intestinal walls and into the bloodstream. The overall reaction that lactase catalyzes is as follows: C 12 H 22 O 11 + H 2 O → C 6 H 12 O 6 + C 6 H 12 O 6 + heat. lactose + H 2 O → β-D-galactose + D-glucose
An example of a prominent glycosyltransferase is lactose synthase which is a dimer possessing two protein subunits. Its primary action is to produce lactose from glucose and UDP-galactose. [41] This occurs via the following pathway: UDP-β-D-galactose + D-glucose UDP + lactose. [42]