plane of plane polarised light in clockwise direction while the levo rotatory compounds rotate in anticlockwise direction. The D or L isomers can either be dextro or levo rotatory compounds. Dextro rotatory compounds are represented as D-(+) or L-(+) and the levo rotatory compounds as D-(–) or L-(–) CHO CH OH D-Ribose CHO HO HO HO CH OH L-Ribose CHO CH OH D-Glyceraldehyde CHO HO CH OH L-Glyceraldehyde CHO HO CH OH D-Glucose CHO HO HO HO CH OH L-Glucose CHO CH OH D-Erythrose CHO HO HO CH OH L-Erythrose Figure . Configuration of carbohydrates .
. Classification of carbohydrates: Carbohydrates can be classified into three major groups based on their product of hydrolysis, namely monosaccharides, oligosaccharides and polysaccharides. XII XII - - - - Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula C n (H O) n .
While there are many monosaccharides known only about of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose Monosaccharides are further classified based on the functional group present (aldoses or ketoses) and the number of carbon present in the chain (trioses, tetroses, pentoses, hexoses etc...). If the carbonyl group is an aldehyde, the sugar is an aldose. If the carbonyl group is a ketone, the sugar is a ketose.
The most common monosaccharides have three to eight carbon atoms. Table . Different types of monosaccharides: No. of carbon atoms in the chain Functional group present Type of sugar Example Aldehyde Aldotriose Glyceraldehyde Ketone Ketotriose Dihydroxy acetone Aldehyde Aldotetrose Erythrose Ketone Ketotetrose Erythrulose Aldehyde Aldopentose Ribose Ketone Ketopentose Ribulose Aldehyde Aldohexose Glucose Ketone Ketohexose Fructose .
. Glucose Glucose is a simple sugar which serves as a major energy source for us. It is the most important and most abundant sugar. It is present in honey, sweet fruits such as grapes and mangoes etc...
Human blood contains about mg/ dL of glucose, hence it is also known as blood sugar. In the