Question

29. Differentiate between the glucose subunits that are joined by the alpha(1,4) glycosidic linkage based on acetal and hemiacetal carbons of the two rings.

30. Describe non-reducing and reducing ring of the disaccharide glucose alpha(1,4) glucose basednon mutarotation of the two rings.

31. Describe how a side chain of amylopectin and glycogen adds non-reducing ends based on aplha(1,6) branch points.

Answer 1

The disaccharide in alpha 1-4 glycosidic bond is present is maltose, both the subunit of maltose is glucose , one subunit have acetal carbon because of formation of glycosidic bond, where as other subunit which is free end has hemiacetal carbon, and act as reducing carbon.

A carbon is said to be a acetal carbon only if an organic molecule where two separate oxygen atoms are single bonded to central carbon atom.

* But hemi acetal is the carbon connected to an alcoho ,an ether ,an R group and a hydrogen. We see hemiacetal carbon only on one side subunit, because OH of other subunit are used in the formation of alpha 1-4 glycosidic bond.

* All the reducing sugar have hemiacetal carbon. But acetal carbon don't have any role in reduction reaction.