GalactoseIdentifiersProperties
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CAS number<26566-61-0>
PubChem6036
MeSHGalactose
Molecular formulaC6H12O6
Molar mass180.08
Melting point

167 levels C

Except where listed otherwise, data are offered for materials in their standard state(at 25 °C, 100 kPa)

Galactose (Gal) is a six-carbon sugar and also a monosaccharide that combines through glucose to kind the disaccharide lactose, develops galactose polysaccharides in agar, is a component in miscellaneous gums, mucilages, and also pectins, and also is likewise present in sugar beets. Together a hexose sugar, galactose has actually the exact same formula as glucose, C6H12O6, yet differs in the place of the hydroxyl group on carbon-4 (Bender and Bender 2005). Along with glucose and fructose, galactose is just one of the 3 most important blood sugars in animals. Galactose additionally is well-known as brain sugar (Houghton Mifflin 1998).

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Galactose is much less sweet than glucose and sucrose. The is thought about a nutritive sweetener because it has food energy. Galactose and also glucose both play vital roles in joining with lipids to type glycolipids and joining v proteins to kind glycoproteins. Galactolipids are a significant component the the membrane tissues of plants, while galactose join in forming the more complex galactocerebrosides action as an important component that membrane tissues in pet muscles and nerves.

Under regular conditions, the elaborate coordination in the human body is remarkable, through lactose in food being broken down, via enzymes, right into glucose and also galactose, and also these sugars being further metabolized. However, in rare cases (one per 62,000 births), this harmonious mechanism is compromised by a hereditary disorder, affecting an individual"s capacity to correctly metabolize the sugar galactose. This leads to toxic levels that galactose building up in the blood, request the removed of lactose and galactose indigenous the diet. This problem is known as galactosemia.


Contents


Description


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Galactose is a six-carbon monosaccharide. As a carbohydrate, galactose belongs come that class of organic molecules the contain mostly carbon (C) atom flanked through hydrogen (H) atoms and also hydroxyl (OH) groups (H-C-OH). As a hexose carbohydrate, galactose has the exact same molecular formula as glucose and also fructose (C6H12O6) however a different atomic arrangement. It different from glucose just in the place of the hydroxyl group on carbon-4 (Bender and Bender 2005). (The carbons of glucose are numbered beginning with the an ext oxidized end of the molecule, the carbonyl group.) In various other words, galactose is an epimer that glucose, having actually a various configuration at only one of several stereogenic centers.

In galactose, the an initial and last -OH groups allude the same means and the second and third -OH groups allude the various other way.

Galactose deserve to be found in two enantiomers, L-galactose and D-galactose. Enantiomers room two stereoisomers the are pertained to each other by a reflection: They space mirror images of each other. Every stereocenter in one has the opposite construction in the other. D-Galactose has the exact same configuration at its penultimate carbon as D-glyceraldehyde.

Galactose is less sweet 보다 glucose and around one-third as sweet as sucrose (Bender and also Bender 2005). It additionally is much less soluble in water 보다 glucose.

Sources and also relationship come lactose

D-galactose is uncovered in such sources as lactose (milk sugar), agar, gum arabic, street beets, seaweed, and also nerve cabinet membranes. L-galactose is discovered in flaxseed mucilage, snail galactogen, agar, and other such sources. Regularly the two forms are found together, creating DL-galactose.

Galactose additionally is synthesized through the body, wherein it forms part of glycolipids and glycoproteins in numerous tissues. Galactose is critical component that cerebrosides, which are glycosphingolipids that room important materials in animal muscle and also nerve cabinet membranes. Myelin is the most famous cerebroside. Cerebrosides consist of a ceramide v a solitary sugar residue in ~ the 1-hydroxyl moiety. The street residue have the right to be either glucose or galactose; the two significant types are as such called glucocerebrosides and also galactocerebrosides. Galactocerebrosides are generally found in neural tissue, when glucocerebrosides are discovered in other tissues.

Galactan is a polymer that the street galactose. That is discovered in hemicellulose and can be converted to galactose by hydrolysis.

Lactose is a main dietary source of galactose for humans. Lactose is a disaccharide that consists of β-D-galactose and β-D-glucose pieces bonded through a β1-4 glycosidic linkage. The hydrolysis of lactose come glucose and also galactose is catalytic analysis by the enzyme lactase, a β-galactosidase. In the human body, glucose is readjusted into galactose in bespeak to permit the mammary glands to secrete lactose. The β-galactosidase enzyme is developed by the lac operon in Escherichia coli (E. Coli).

Liver galactose metabolism

Galactose in the bloodstream travels to the liver. In the liver, galactose (Gal) is converted to glucose-6-phosphate (Glc-6-P) in the complying with reactions:

galacto- uridyl phosphogluco- kinase transferase mutase festival --------> festival 1 ns ------------------> glc 1 p -----------> glc 6 ns ^ / v UDP-glc UDP-gal ^ / \___________/ epimerase

Enzymes that catalyze the reactions space in italic. Mutations that disable either the kinase, the transferase, or the epimerase block galactose metabolism, producing galactosemia. The cyclic reaction at the center of the diagram mirrors that uridyl-transferase catalyzes Gal-1-P and also UDP-Glc (uracil-diphosphate-glucose) to react in such a way that the festival displaces the Glc from its bond v UDP yielding UDP-Gal and also Glc-1-P. (Biocarta)

Clinical significance

Some studies have suggested a feasible link between galactose in milk and also ovarian cancer (Cramer 1989; Cramer et al. 1989). Other studies display no correlation, even in the visibility of defective galactose management (Goodman et al. 2002; Fung et al. 2003). More recently, pooled evaluation done by the Harvard college of Public health showed no specific correlation in between lactose comprise foods and ovarian cancer, and showed statistically insignificant boosts in hazard for consumption of lactose at ≥30 grams/day (Genkinger et al. 2006). An ext research is necessary to ascertain feasible risks.

Some recurring studies indicate that galactose may have actually a duty in treatment of focal length segmental glomerulosclerosis (a kidney an illness resulting in kidney failure and proteinuria). This result is most likely to be a result of binding the galactose come FSGS factor.

Metabolic disorders


Main article: Galactosemia

There room some essential disorders including galactose.

Galactosemia is a rare hereditary metabolic disorder the affects an individual"s ability to correctly metabolize the sugar galactose. Goppert first described the disease in 1917 (Goppert 1917), with its cause as a defect in galactose metabolism being determined by a team led by Herman Kalckar in 1956 (Isselbacher et al. 1956). Incidence that the most typical or classic form of galactosemia is around one per 62,000 births (Merck).

References

Goppert, F. 1917. Galaktosurie nach Milchzuckergabe bei angeborenem, familiaerem chronischem Leberleiden. Klin Wschr 54:473-477.

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Types that Carbohydrates
General:
Aldose | Ketose | Pyranose | Furanose
Geometry
Triose | Tetrose | Pentose | Hexose | Heptose | Cyclohexane conformation | Anomer | Mutarotation
Small/Large
Glyceraldehyde | Dihydroxyacetone | Erythrose | Threose | Erythrulose | Sedoheptulose
Trioses
Ketotriose (Dihydroxyacetone) | Aldotriose (Glyceraldehyde)
Tetroses
Erythrulose | Erythrose | Threose
Pentoses
Arabinose | Deoxyribose | Lyxose | Ribose | Ribulose | Xylose | Xylulose
Hexoses
Glucose | Galactose | Mannose | Gulose | Idose | Talose | Allose | Altrose | fructose | Sorbose | Tagatose | Psicose | Fucose | Fuculose | Rhamnose
Disaccharides
Sucrose | Lactose | Trehalose | Maltose
Polymers
Glycogen | strength (Amylose | Amylopectin) Cellulose | Chitin | Stachyose | Inulin | Dextrin
Glycosaminoglycans
Heparin | Chondroitin sulfate | Hyaluronan | Heparan sulfate | Dermatan sulfate | Keratan sulfate
Aminoglycosides
Kanamycin | Streptomycin | Tobramycin | Neomycin | Paromomycin | Apramycin | Gentamicin | Netilmicin | Amikacin
Major family members of biochemicals
Peptides | Amino mountain | main point acids | carbohydrate | Nucleotide sugars | Lipids | terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids: Analogues of nucleic acids:


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