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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.
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 ...
An example is the glucose symporter SGLT1, which co-transports one glucose (or galactose) molecule into the cell for every two sodium ions it imports into the cell. [27] This symporter is located in the small intestines, [28] heart, [29] and brain. [30] It is also located in the S3 segment of the proximal tubule in each nephron in the kidneys. [31]
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
Galactose uses the same transport system. Fructose, on the other hand, crosses the apical membrane of the enterocyte, using GLUT5. It is thought to cross into the blood capillary using one of the other GLUT transporters. Peptide and amino acid uptake. Peptidases in the glycocalyx cleave proteins to amino acids or small peptides.
After separation from glucose, galactose travels to the liver for conversion to glucose. [12] Galactokinase uses one molecule of ATP to phosphorylate galactose. [2] The phosphorylated galactose is then converted to glucose-1-phosphate, and then eventually glucose-6-phosphate, which can be broken down in glycolysis. [2]
In pancreatic beta cells, free flowing glucose is required so that the intracellular environment of these cells can accurately gauge the serum glucose levels. All three monosaccharides (glucose, galactose, and fructose) are transported from the intestinal mucosal cell into the portal circulation by GLUT2. Is a high-frequency and low-affinity ...
The galactose permease or GalP found in Escherichia coli is an integral membrane protein involved in the transport of monosaccharides, primarily hexoses, for utilization by E. coli in glycolysis and other metabolic and catabolic pathways (3,4).