Occurrence It is an important component of malt. Maltose does not occur in the human body. It is produced when starch is hydrolysed by α-amylase.
Disaccharides are carbohydrates that consist of two molecules of the same or different monosaccharides. During hydrolysis, a disaccharide yields two moles of monosaccharides. The mode of linkage between these monosaccharides is the glycosidic linkage. The general molecular formula is CnH2nOn−1. Examples Maltose Glucose glucose + (reducing sugar)Lactose Galactose + glucose (reducing sugar)Sucrose Glucose + fructose (non reducing sugar)
Esterification of carbohydrates with phosphoric acid usually happens in metabolism. For example, glucose-6-phosphate and glucose-1-phosphate are formed during metabolism. ATP donates the phosphate group for esterification.
Amino sugars are formed when the hydroxyl group is replaced by an —NH2 group. Examples are glucosamine and galactosamine. Amino sugars occur as N-acetyls in numerous biological important compounds. N-acetyl derivative of D-glucosamine is present in hyaluronic acid, heparin, and some blood group compounds. Galactosamine is present as N-acetylgalactosamine in chondroitin sulphate. Antibiotics such as erythromycin…
Deoxy sugars are the sugars in which the oxygen in the —OH group has been removed leaving the hydrogen. Thus, the —CHOH or —CH2OH becomes —CH2 or —CH3. Deoxy sugars are 2-deoxy-D-ribose found in nucleic acid (DNA) and 6-deoxy-L-galactose found as a constituent of bacterial polysaccharides.
D-glucuronic acid is present as the chief constituent of certain mucopolysaccharides. This is involved in the detoxication mechanism, where bilirubin is linked with D-glucuronic acid.
Uronic Acids Uronic acid is formed when glucose is oxidised such that its primary alcohol group is converted to COOH group, without the oxidation of the aldehyde group. Examples D-glucose D-glucuronic acidD-galactose D-galacturonic acid In the body, glucuronic acid is formed from glucose in the uronic acid pathway in the liver.
Glycosides are present in many drugs and spices. They are also the chief constituents of animal tissues. Aglycones are methanol, glycerol, sterol, or phenol. Glycosides play a very important role in medicine because of their action in heart (cardiac glycosides). Examples are the derivatives of digitals and ouabain. Ouabain is a very good inhibitor of Na+—K+—ATPase…
Glycosides are produced by the interaction of monosaccharide residue with the hydroxyl group of a second compound, which may be a monosaccharide or some other compound. The non-carbohydrate compound is called an aglycone. The glycosidic bond is formed as an acetal link between a hemiacetal and a —OH group. Sugar—H + R—OH Sugar—R (Glycoside) +…
Osazone reaction is possible only when a free carbonyl (aldehyde or ketone) group is present. A monosaccharide or reducing disaccharide is first mixed and heated with phenylhydrazine in acetic acid to form sugar-phenylhydrazine, which then reacts with more reagents to form particular osazone-forming characteristic crystals of specific shapes. This test is very important to distinguish…