This is for mscdfsm ,#medical #nursing #biology #neet #foodandnutrition #biochemistry and #related subjects .also it will help #dieticians to upgrade their skills

1. MSCDFSM BIOCHEMISTRY
CARBOHYDRATE II

2. OPTICAL ISOMERSISM
A compound is optical active when it can rotate the ray of polarized
light .this is possible because of presence of asymmetric carbon atom
Two compounds that have similar molecular formula can have
different optical activity .
When a compound rotate the plain of polarized light in clockwise
direction it is called dextro rotatory
When a compound rotate the plain of polarized light in anti clockwise
direction it is called Levo rotatory .
D and L ISOMERS are also known expressed as + and – respectively
Eg D-glyceraldehyde and L –glyceraldehyde .
CYCLIC FORMS OF MONOSACHHARIDES
Aldohexoses ,aldopentoses and ketohexoses undergo cyclization when
treated with alcohol and form hemiacetal or hemiketal ring.it results
in linkage of carbonyl carbon atom withother carbon atom by c-o-c
linkage
it results in 6 membered ring (pyranose )or 5
membered ring called furanose

3. The ring form has an additional asymmetric carbon atom called
anomeric carbon atom .due to asymmetry of c1 two ring form alpha and
beta are possible .with different optical rotation called mutarotation.
MUTAROTATION it is the process where by the confugration of anomeric
carbon convert from alpha and beta and vice versa.the ring form of
sugars containing asymmetric carbon atom exist in alpha and beta
anomers
Anomers are cyclic sugarsthat differ ony in position of substituents at
hemiacetal carbon atoms. In alpha form the –OH GROUP IS PRESENT at
opposite side of CH2OH and in beta group the –OH group is present at
same side .REF FIG 1.7 PAGE 14. EG ..alpha –D-glucose and
beta- D-glucose
PROPERTIES OF MONOSACHHARIDES
• ESTERIFICATION
• OXIDATION
• REDUCTION
• OSAZONE
• FURFURAL REACTIONS

4. MONOSACHARIDES PROPERTIES
1. Monosachharides are water soluble ,colourless,odourless,sweet crystals.
2. ESTERIFICATION : Monosaccharides have -0H group .they form esters with acids
.In nutritional biochemistry phosphoric acid esters are of great significance as
they are metabolic intermediates of glucose or fructose.
Eg .fructose 1,6 –bisphosphate
3. OXIDATION REACTION : aldoses gets converted to aldonic acids when react to
mild oxidizing agents like NAOI (sodium hypoiodite) and bromine water .it is due to
the presence of –CHO group that gets converted to –COOH (carboxylic group)
Eg .glucose gets converted to gluconic acid .
On other hand if they react with strong oxidizing agent likenitric acid ,aldose gets
converted to aldaric acid .here both –CHO and –CH2OH group gets converted to –
COOH . Eg .glucose get converted to Glucaric acid .
This reaction is not performed by ketones so we can use this reaction to
distinguish between aldose and ketose .
Dilute HCL oxidise terminal –CH2OH with formation of uronic acid eg .glucose is
oxidized to glucurnic acid .
D-glucose D –glucuronic acid

5. This is the basis of fehling test .in fehling test the free sugar group reduces
the cupric ions in alkaline medium to form cuprous oxide and sugar gets
oxidized to carboxylic acid .the CU2O is red and precipitates carbohydrate that
react in basic solution with oxidizing agents are called reducing sugars .
REDUCTION REACTION
Aldoses and ketoses are reduced to polyhydroxy alcohol by sodium borohydride
,sodium amalgam eg. Glucose is reduced to glucitol .
Polyhydric alcohol are also called sugar alcohol and are hydrogenated form of
aldoses and ketoses.glucitol is also called sorbitol
Sugar alcohol have half the calorie of sugar and are used as low calorie product
D- glucose +2H D-glucitol
OSAZONE REACTION
When a monosaccharide is heated with phenylhydrazine in acetic acid ,the
carbonyl group of monosaccharide react with phenylhydrazine to form osazone
FURFURAL FORMATION
Monosaccharide when treated with concentrated mineral acid they get
converted to furfurals .