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Lactose can not be absorbed by the intestine and needs to be split in the small intestine into galactose and glucose by the enzyme called lactase; unabsorbed lactose can cause abdominal pain, bloating, diarrhea, gas, and nausea. [citation needed] In most mammals, production of lactase diminishes after infants are weaned from maternal milk.
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.
Glucose-galactose malabsorption generally becomes apparent in the first few weeks of a baby's life. Affected infants experience severe diarrhea resulting in life-threatening dehydration, increased acidity of the blood and tissues (), and weight loss when fed breast milk or regular infant formulas.
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
After the ingestion of lactose, most commonly from breast milk for an infant or cow milk and any milk from an animal, the enzyme lactase hydrolyzes the sugar into its monosaccharide constituents, glucose and galactose. In the first step of galactose metabolism, galactose is converted to galactose-1-phosphate (Gal-1-P) by the enzyme galactokinase.
Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides; common examples are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose).
Infants with classic galactosemia cannot be breast-fed due to lactose in human breast milk which consists of both galactose and glucose and are usually fed a soy-based formula. [ 24 ] Galactosemia is sometimes confused with lactose intolerance , but galactosemia is a more serious condition.
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.