Everything about Disaccharides totally explained
A
disaccharide is a
sugar (a
carbohydrate) composed of two
monosaccharides.
'Disaccharide' is one of the four chemical groupings of carbohydrates (
monosaccharide, disaccharide,
oligosaccharide, and
polysaccharide).
Classification
There are two basic types of disaccharides: reducing disaccharides, in which the monosaccharide components are bonded by
hydroxyl groups; and non-reducing disaccharides, in which the components bond through their anometric centers.
Formation
It is formed when two sugars are joined together and a molecule of water is removed. For example; milk sugar (
lactose) is made from
glucose and
galactose whereas cane sugar (
sucrose) is made from
glucose and
fructose.
The two
monosaccharides are bonded via a
dehydration reaction (also called a
condensation reaction or dehydration synthesis) that leads to the loss of a molecule of water and formation of a
glycosidic bond.
Properties
The glycosidic bond can be formed between any hydroxyl group on the component monosaccharide. So, even if both component
sugars are the same (for example,
glucose), different bond combinations (regiochemistry) and stereochemistry (
alpha- or
beta-) result in disaccharides that are
diastereoisomers with different chemical and physical properties.
Depending on the
monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water-soluble, and sometimes sweet-tasting and sticky-feeling.
Common disaccharides
Maltose and cellobiose are
hydrolysis products of the
polysaccharides,
starch and
cellulose, respectively.
Less common disaccharides include:
Gentiobiose, that consists of two
glucose monomers with an β(1→6) linkage;
Isomaltose, that consists of two
glucose monomers with an α(1→6) linkage;
Kojibiose, that consists of two
glucose monomers with an α(1→2) linkage ;
Laminaribiose, that consists of two
glucose monomers with a β(1→3) linkage;
Mannobiose, that consists of two
mannose monomers with either an α(1→2), α(1→3), α(1→4), or an α(1→6) linkage;
Melibiose, that consists of a
glucose monomer and a
galactose monomer with an α(1→6) linkage;
Nigerose, that consists of two
glucose monomers with an α(1→3) linkage;
Rutinose, that consists of a
rhamnose monomer and a
glucose monomer with an α(1→6) linkage; and
Xylobiose, that consists of two
xylopyranose monomers with a β(1→4) linkage.
Further Information
Get more info on 'Disaccharides'.
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