MONOSACCARIDE:
Monosaccarides are true carbohydrate that are either a polyhydroxy aldehydes or polyhydroxy ketone. The number of carbon atom in monosaccarides is from 3 to 7 . All carbon atoms in monosaccarides has hydroxy group except one which is a part of aldehyde or ketone. The general formula for monosaccarides is Cn(H20)n, where, n is the number of carbon atoms in monosaccaridesCLASSIFICATION OF MONOSACCARIDE:
Monosaccarides are classify on the based of functional group and number of carbon atom. Monosaccarides that have aldehyde functional group is called ALDOSES. While those contain ketone functional group is called KETOSES. On the other hand monosaccarides are classify on five groups based on number of carbon atom1-Trioses(3C)
2-Tetroses(4C)
3-Pentoses(5C)
4-Hexoses(6C)
5-Heptoses(7C)
Monosaccarides are very sweet in taste and all are soluble in water
CHEMICAL STRUCTURE OF MONOSACCARIDE:
Monosaccarides are usually found in open chain structure in dried form but they change into ring chain structure when dissolve on water. Two types of ring formed in monosaccarides1-Furanose ring
2-Pyranose ring
FURANOSE RING:
It is a five membered ring in which one oxygen and four carbon atom are found, oxygen is link with C1 and C4. All pentoses and ketohexoses form furanose ring
PYRANOSE RING:
It is six membered ring in which one oxygen and five carbon atom are found, oxygen is linked with C1 and C5. All aldohexoses form pyranose ring
UNDERSTANDING BY EXAMPLE:
Let understand this by example;Ribose is an aldopentose sugar with chemical formula (C5H10 O5). It is found in open chain structure in dried form but when it dissolve in water it change to furanose ring. When it dissolve in water oxygen atom from aldehyde group react with penultimate carbon(second last carbon) in this way oxygen atom forms a link between C1 and C4 while oh group from C4 shift to C1. After this modification ring structure form. The ring structure demonstrated by EMIL FISCHER is called FISCHER PROJECTION(Two dimensional representation of ring structure) while that represented by English chemist NORMAN HAWORTH is called HAWORTH PROJECTION(Three dimensional representation of ring structure)
STERIOISOMERISM IN MONOSACCARIDE:
Those isomers in which -H and -OH group are arranged in different pattern to the asymmetric carbon atom is called sterioisomers. Asymmetric carbon atom are those which make bond with four different atom around it for example in case of glucose C2,C3,C4, and C5 are asymmetric carbon atom. In monosaccarides the number of sterioisomer is actually depend upon number of asymmetric carbon atom abd can be determined by formula 2n where n is the number of asymmetric carbon atom, so glucose has 16 sterioisomers. Sterioisomers are classified into three groups1-Enantiomers
2-Disterioisomer
3-Epimers
ENANTIOMERS::
Those sterioisomers which are non-superimposible image of oneanother are called enantiomers. An example of enantiomers are D and L isomers of glucose. In D isomer the OH group on penultimate carbon or C5 caron is present on right side while in L isomer the OH group is present on left side. Out of 16 sterioisomers of glucose 8 are enantiomers of other 8
DISTERIOISOMERS:
Those sterioisomers which have different arrangment of H and OH on more then one asymmetric carbon atom is called disterioisomers. Examples are D-GLUCOSE and D-ALTROSE
EPIMER:
Those sterioisomers which have different arrangment of H and OH groups at only one asymmetric carbon atom is called EPIMERS. Examples are D-GLUCOSE and D-MANNOSE
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