Monosaacharides are poly hydroxy aldehydes ,or ketones,Which can not be further classified into simple sugar.

1. J.Mythili
Assistant professor of department of
Biotechnology,
Bonsecours college for women

2.  Monosaccharides are poly hydroxy aldehydes or ketones which cannot be
further hydrolyzed to simple sugars (Mono- single, saccharide –sugar)
 Monosaccharides are simple sugar .they are sweet in taste.
 They contain 3 to 10 carbon atoms ,2 or more hydroxyl (OH)group s and
one aldehyde (CHO)group ,or one ketone group (CO) group.
 They are represented by the formula of (CH2O)n.
 The monosaccharides contain one or more asymmetric carbon atoms. the
asymmetric carbon atoms attached to four different groups.

3.  Monosaccharides are classified in two ways ,first up all based on the
number of carbon atoms present in in them , monosaccharides are
classified in to
 Trioses containing 3 carbon atoms C3 H6 O3
 Tetroses containing 4 carbon atoms C4 H8 O4
 Pentoses containing 5 carbon atoms C5 H10 O5
 Hexoses containing 6 carbon atoms C6 H10 O6
 Hep toses containing 7 carbon atoms C7 H10 O7
 Secondly based on the type of carbonyl group ,monosaccharide s classified
in to two types,
 Namely aldoses having an aldehyde group and ketoses having a ketone
group .
 Both aldoses and ketoses have the suffix- ose. Inorder to differentiate
them, ketoses are named with suffix- ulose.

7.  Glucose is a simple monosaccharide.it is hexose .It is an aldohexose
 The molecular formula of glucose is C6 H12 O6.
 The glucose may be represented by two structures .they are
1.Straight chain structure or open chain structure
2.Cyclic structure or ring structure
1.Straight chain structure or open chain structure.
 In straight chain structure ,the carbon atoms o glucose are arranged in
straight chain line.it is also called open chain structure because the two
ends remain separate and they are not linked.
 Fitting and Baeyer proposed in straight chain structure .It contains
aldehyde group (CHO) and hydroxyl groups (OH).
 According to fitting Baeyer,the aldehyde group is at one end and four
CHOH groups in between.

8. C6H12O6 CHO CHO
I I
(CH.OH)4 H - C -OH
I I
CH2OH HO - C- OH
Molecular I
formula fitting H-C-OH
Baeyer I
straight H-C-OH
chain I
CH2 OH
Fisher straight chain
structure

9.  Fisher’s proposed another straight chain structure .according to fisher’s
the aldehyde group is placed at one end and the remaining carbon atoms
are arranged one behind the other.
 The last carbon atoms contains two hydrogen atoms and other OH Group
(H2OH).
 The remaining carbon atoms contain H atom on one side and OH group
on the other side.
 The carbon atoms are numbered from the aldehyde group .The carbon
atom of the aldehyde group is the carbon atom number 1 and carbon atom
containing H2 OH is the carbon atom number 6 in (Hexoses).

10.  In cyclic structure ,the atoms are arranged in the form a ring .Haworth
(1929) an English chemist ,deviced the ring structure .Hence the ring
structure is referred to as Haworth’s projection formula.
 The sugar molecules exist in two types of rings .they are pyranose ring
and furanose ring.
 The ring structure of monosaccharides may be similar to either pyran or
furan and accordingly the monosaccharide is said to occur in pyronose
orfyronose form.