Define the Meaning of Isomerism?
All monosaccharides exhibit isomerism. An asymmetric carbon or chiral carbon contains four different groups attached to it. The formula 2n determines the number of isomers possible, where n is the number of chiral carbons or asymmetric carbons. All monosaccharides except dihydroxyacetone contain one or more asymmetric carbons (or chiral carbons or chiral centre) and thus occur in optically active isomeric forms.
The simplest three-carbon aldose, glyceraldehyde contains only one chiral carbon and thus is capable of existing in two isomeric forms. The 6 carbon aldohexoses have four chiral carbons and are capable of existing in 24 = 16 isomeric forms. Amongst the sixteen hexoses, D- glucose is the most common and physiologically the most important form.