Carbohydrates

Monosacchrides
(A) Classification (B) Structure cyclization (C) Joining
Aldoses ketose Isorners Epimers Enantiomers DI- Oligo- Poly-
Containing
Aldehyde gp keto gp
H – C - = O I
I C = O
I
D – Sugar L – sugar linear Branch
The bonds that link
sugars.
e.g.,
(starch) (glycogen)
Glycosiclic
bond,

CARBOHYDRATE
→ Polyhydroxylated compounds ē at
least 3 – carbon atoms ē potentially
active carbonyl group which may either
be aldehyde, or ‘ketone’ groups.
→ Also called sacchrides / sugar
→ Empirical formula (CH20)n

Classification of
carbohydrates
1 – Monosaccharides.
2 – Disaccharides.
3 – polysacchrides.
4– Derived Carbohydrates
Oxidation and reduction products
Amino and Deoxy sugars.
Homopolysacchrides
Heteropolysacchrides Mucopolysacchrides
Mucilages
Hemicellulose

(1). Monosacchrides
“ simple sugars ḛ Cannot be further
hydrolysed”
→ they are either aldoses containing
aldehye group or ketoses containing
ketone group.
→ white crystalline solids
→ very soluble in water.
→ most have sweet taste
H R
I I
C=O C=O
I I
R R
Aldehyde ketone
group group

Generic
Names
Aldoses Ketoses
Trioses (C3H6 03) glycerose/
Glyceraldehydes
dihydroxyacetone
Tetroses (C4 H8O4) Enythrose Erthrulose
Pentoses (C5H10 O5) Ribose Ribulose
Hexoses (C6H10 O6) Glucose Fructose
Heptoses (C7H14 O7) Glucoheptose sedoheptulose

(2). Oligosaccrides
“Condensation products of 3 – 10
monosacchrides”
Most are not digested by human
enzymes.
Monosacchrides attach each other by
glycosidic linkages.

For example,
 - Dextrin ( polymer of 8 – glucose
molecules)
Maltolriose ( polymer of 3 glucose
molecules )
Isomaltose and trehalose.

(3). disacchrides
“Condensation products of 2 monosacchrides
For Example
Maltose (glucose + glucose).
Sucrose (glucose + fructose).
Lactose (glucose + galacose)
→ hydrolysis of sucrose produces a mixture of
glucose and fructose called “Invert sugar”
b/c fructose is strongly levorotatory and
changes the weaker dextrorotatory action of
sucrose.

(4). Polysaccharides
“condensation products of
>10 monosacclrides”
→ they serves as stores of fuel.
→ forms structural elements of cells.
(a). Homopolysacclrrides.
They contains only one type of
monosacchrides e.g., starch, glycogen,
cellulose and dextrins.

(b). Heteropolysacchrides.
They contain a no of diff.
monosacchrides e.g.,
Mucopolysacchrides
Hyaluronic acid, heparin, chondroitin
sulphate, blood group polysacchrides,
serum mucoid .
Mucilages
Agar, vegetasle gums and pectin.
Hemicellulose .

(5). Derived carbohydrates
Derived from carbohydrates by
various chemical reactions.
(a). Oxidation products derived from
glucose on its oxidation e.g., gluconic
acid, glucuronic acid, glucaric acid
and ascorbic acid (vits).
(b). Reduction products
glycerol and ribitol derived from
glyceraldehydes and ribose.

( c). Amino sugar
These have NH2 group at carbon
No 2 include glucosamine,
galactosamine, manosamino derived
from glucose galactose and manose
respectively.
(d). Deoxy- sugar
They have less no of oxygen atoms
than parent sugar e.g.,
2 – deoxyribose present in DNA has
one oxygen atom less as compared to
ribose.

Structure of monosacchrides
(1). Isomers
“ compounds that have same chemical
formulas” e.g., glucose, galactose, fructose
and mannose all have same chemical formula
C6H12O6 (hexoses).
(2). Epimers
“Two isomers ḛ differ in configration
around one specific Carbon atom other
than the carbon atom of carbonyl group
called epimers.
Glucose and galactose → carbon 4 epimers
Glucose and mannose → carbon 2 epimers.

¹CHO ¹CHO
I I
H – C2 – OH H – C2 - OH
I I
H – C3 – OH H – C3 – OH
I I
OH – C4 – OH H – C4 – OH
I I
H – C5 – OH H – C5 – OH
I I
H – C6 – OH H – C6 – OH
I I
H H
¹CHO ¹CH2OH
I I
OH – C2 – H C2 =O
I I
H – C3 – OH OH – C3 – H
I I
H – C4 – OH H – C4 – OH
I I
H – C5 – OH H – C5 – OH
I I
H – C6 – OH H – C6 – OH
I I
H H
Aldoses Keto sugar
Galactose Glucose Mannose Fructose
C4- epimers C2 – epimers
all Isomers of each other

Enantiomers or optical
isomers or stereoisomers
NAMING ENANTIOMERS
(a) By configration D – sugar
L – sugar
(b) By Optical Activity
Levorotatory ‘l’/- ve
(3)
Dextrorotatory ‘d’/+ ve

Levorotatory and dextrotatory
substances
Substance moving the plain
polarized light to the left and right are
called levo. and dextrorotatory
respectively as ‘l’(-ve) and ‘d’ (+ve)
→ optical activity of sugar is dlt
presence of asymmetrical c. atoms

As Dihydroxyacetone has no
asymmtric carbon so it has no optical
activity.
¹CH2OH
I
²CH = O
I
³CH20H
→ Enantiomers have some physical and
chemical properties bt rotate PPL in
opposite directions.

POLARIMETER
The instrument ē which optically active compounds
are studiedis a polarimeter
Emergent
Light ē rotated
Plane of the polarizationNicol
Prism
Polarizer
The rotation in degree of
/ gm of substance /ml of the
Solvent in a tube of one dm
(10 Cm )in length in called
Specific rotation
Unpolorized
Light osscilating
in all planes
(source)
Incident
Plane – polarized
Light osscilating
In one plane
Polarimeter
Tube containing
Sol of an optical
Isomer
Nicol
prism
analyzer
Levorotatory Dextrorotatory
Anticlockwise clockwiseT = temp of rotation
D = Na light ʎ (589 nm)
Obs = observed rotation in a tuse C = conc of substance g/ml
L = length of tuse in dm [ ] = rotation
[ ] = obs
D l x C
T

(3). Enantiomers
“ a pair of structures that are mirror
images of each other in regard to
asymmetric carbon atoms present in
their molecules” e.g.,
Glucose occurs as D and L glucose
isomers.
The name D and L depends upon the
position of OH group on the last
asymmetric cabon atom ( to which 4 diff
atoms or groups are attached) of
monosacchride.

C¹HO C¹HO
I I
H – C2 – OH HO – C2 – H
I I
OH – C3 – H H – C3 – OH
I I
H – C4 – OH HO – C4 – H
I I
H – C5 – OH HO – C5 – H
I I
CH20H CH20H
D – glucose L – glucose
6 6
mirror

→ The structure of the smallest sugar
containing 3 – C atoms namely
Glyceraldehydes also called “ Referance
sugar”
C¹HO C¹HO
I I
H – C2 – OH OH – C2 – H
I I
H – C3 – OH H – C3 – OH
I I
H H
D – glyceraldehyde L – glyceraldehyde

(a). D – sugars
all such sugars whose asymmetric C
– atom situated farthest from the
potential aldehyde or ketone gp has
the same configration as the
asymmetric C-atom of
D- glyceraldehyde are called D –
sugar.

(b). L – Sugars
All sugars whose carbon atom
situated farther from the potential
aldehyde or ketone gp has the same
configration as the asymmetrical c.
atom of L – glyceraldehydes are
called L – sugars.

CYCLIZATION
(Hemiacetal/ Hemiketal rings) pyranose
furanose
Anomeric 1 Mutarotation 2 Representation 3 Anomers 4
Carbon
v
Fischer projection formula.
Haworths ‘’ ‘’ ‘’
Boat and chair forms
 - sugar.
Β – sugar .
Anomeric
Isomers
or
diast-
Ercomers.
OH gp not altach Covallently attach
To other molceule to other molecule
Ring open and aldehyde if attach to if attach
gp of acyclic sugar - OH gp to – NH2 gp
Oxidized
Reducing sugar O – Glycoside N – glycosidic
linkage likage
v
5 Glycosidic
Bone
V

Cyclization of monosacchrides
Each Monosacchride exists in
Open chain (acyclic) form and
predominantly in ring form.
Hemiacetal or Hemeketal ring
Aldehyde or Keto group has reacted ē
an alcohol group on the same sugar to
from hemiacetal or hemiketal ring.
(4).

(a). Pyranose ring
if resulting ring has 6 members (5C and 1 oxygen).
(b). Furanose, ring
if it is 5 membered (4C and 1 oxygen)
(1). ANOMERS
aldehyde/ keto gp cyclize to produce
ammonic C atom.
These are isomers that differ in
configration around the anomcric carbon
atom i.e., the carbon atom of the carbonyl
group carbon No 1 in aldoses and
carbon No 2 in ketoses.

OH H H OH
C C
I I
H – C – OH H – C – OH
I I
β – D OH – C – H H0 – C – H
I I
H – C - OH H – C – OH
I I
H – C - H – C
I I
H – C – OH H – C – OH
I I
H H
β – D glucopyranose - D Glucopyranose
The 2 types anomers called and - β anomers.

(2). Mutarotaion
Thy cyclic and β anomers of sugar
in a solution can readily be
interconverted and are in equillibrium
with each others
e.g., a sotuain of pure D – glucose in
water.
Produces an equilibrium mixture of
about 64% β – D glucose and 36 % - D
glucose.

OH H O H OH
II
¹C C – H ¹C
I I I
H - ²C – OH H – C – OH H - ²C- OH
I I I
HO - ³C – H HO – C – H HO - ³C – H
I I I
H – C – OH H – C – OH H – C – OH
I I I
H – C - H – C – OH H – C
I I I
H – C – OH H – C – OH H – C – OH
I I I
H H H
β – D glucopyranose
+19º (64%)
D – glucose - D glucopyranose
(36%) +112º

It is dlt the fact that being dissolved in
water the glucose molecules going on
changing from one to another from each
having a diff. optical rotation of polarized
light. An equilibrium is reached after the
passage of sometime and the specific
rotatin becomes fixed.

(3). representation of sugar
conformation.
H OH
C1
I
H – C – OH
I
HO – C – H
I
H – C – OH
I
H – C –
I
H – C – OH
I
H
(a). Fischer Projection formula
carbon chain is written
vertically ē C1 at the top.
- D glucose

Carbon 1 is drawn farthest to the right and
- H , - OH and CH20H projects either above
and below the plane of paper.
(b). Haworth projection formula

5 H 5 H H 5 OH
H H
4 1 4 1 4 1
OH H OH H
3 2 3 2 3 2
OH H
1 → 5 ring H OH H OH
pyran
CH20H CH20H
6 6
β – D glucopyranose- D glucopyranose

O O O
CH20H CH20H
I I
H – C – OH H – C – OH
H OH
4 1
3 2 3 2
OH H OH H
H OH H H
4 1
3 2
1 – 4 ring H OH H OH
Furan - D glucofuranose β – D glucofuranose
6 6
5 5

( C). Boat and Chair forms.
Provides more exact representation
of the three diamentional conformation
of sugar in nature.

Glycosidic Bonds
Glycosidic bonds B/w sugar are
named according to no of connected
carbons and ē regard to the position of
anomeric. – OH gp of sugar involved
in the bond.
oThe linkage is an bond if anomeric
OH is in configration.
oThe linkage is a β – bond if anomeric
OH is in β – configration.
(4).

β – Galactose β – Glucose
→ Lactose β(1 – 4 glycosidic bond)
is reducing sugar b/c anomaric end
of glucose is not involved in glycosidic
linkage.
CH2OH CH2OH
O O
OH H OH
O
5 5
4 1 4 1
OH OH
3 2 3 2 H
OH OH
6 6
H

CHEMICAL PROPERTES OF
MONOSACCHRIDES
(1). Reacting ē hydrazine's to form osazones.
Meating of sugars containing aldehyde or ketone group
ē phenylhydrazine produces phenylosazones e.g.,
Glucose + 3(C6H5NHH2) → glucosazone +
C6H5NH+NH3 + 2H20
fructose, glucose and mannose form identical
osazones called glucosazone.

Galactose → Galactosazone.
Maltose → Maltosazone.
Lactose → lactosazone.
Lactose and maltose forms osazones
crystals.
Sucrose not form osazones.
(2). Reduction to form sugar Alcohol.
Both aldoses or ketoses may be
reduced at their addehyde and ketone
groups to produce corresponding
polyhydroxy alcohol.

Glucose → sorbitol
Manose → Manitol
Fructose → sorbitol + manitol
glyceraldehyde → Glycerol
Ribose → Ribitol
MANITOL is used in pt ē cerebral
edema b/c it acts as osmotic diuretic
and ↓es water content of body thus
↓es Brain swelling.

SORBITOL
Get deposited in the lense of eyes of
diabetic pt and contribute to Cataract
formation.

(3). Oxidation to produce sugar
acids.
On oxidation give 3 types of sugar acids.
Gluconic acid → at C1.
Glucuronic acid – at C6.
Gluconic acid – both at C1 and C6.

GLUCURONIC ACID.
→ It is used in the process of detoxifying
and inactivating many substances in
body like benzoic acid, steroid
hormones and bilirubin.
→ In all plants and mammals it is used as
a precursor of Ascorbic acid (vitc)

(4). Reduction Action of sugar in
Alkaline solution.
Any of the sugar containing potentially
free aldehyde or ketone groups
possesses the property of readily
reducing alkaline solutions of many
mettalic salt such as Cu Ag, Bi , Hg ,
Fe.
+2 + +3
+ +3

Examples of reducing sugar.
Glucose, galactose, glyceraldehydes
lactose and maltose.
Non reducing sugar. Sucrose and
trehalose, glycosides.
→ Test used for detection of
presence of red. Sugar.
Benedicts reagent.
Fehling’s solution.

(5). Action of Acids.
Monosaccharide's are resistant to
actions of hot dilute mineral acids. Strong
acid remove water from sugar to form
organic compocuds furfurals
C5H10 05 → C5 H4 O2 + 3H2o
(6). Action of Bases
Dilute basic solutions at low temp can
bring about a rearrangement of groups
around anomeric C. atom and its
adjacent C. atom e.g., glucose can be
changed to fructose and mannose.

(7). Formation of Esters
The OH group of sugars may be
esterified to form Estes.
Such as phosphates, acetates,
proprionates,
Sugar phosphate back bone form the
structural framework of nucleic acid
(DNA and RNA).

(8). Formation of amino sugars
The OH group of monosacdride can
be replaced by an amino (- NH2) group
forming an amino sugar e.g.,
D – glucosamine → hyaluronic acid.
D – galactosamine → Chondroitin.
D – manosaming → mucoprotein.
Amino sugars also present in antibiotics
e.g., in Erythromycin.

(9). Fermentation.
Breakdown of sugars by bacteria and
yeasts using a method of respiration. ē out
oxygen (anrerobic).
C6H12O6 → 2 C2H5OH + 2CO2
(glucose) (ethanol).
Uses production of
Yogurt.
Alcoholic Beverages.
Pickles
Bread.
Fuel.

(10). Formation of Glycosides.
Glycosides are compounds in ḛ a
carbohydrate residue (e.g., glucose)
is attached by an acetal linkage at
anomeric C . atom to an alcohol
residue called a glycon ḛ is non-
carbohydrate.
→ Aglycon attach to sugar thr. OH gp or
– NH groups. forming
O – and N – glycoside respectively.

For example
Sugar + asparagine → N – glycosidic bond.
Sugar + serine → O – glycosidic bond.

H OH H
C C
I I
H – C – OH H – C – OH
I I
HO – C – H HO – C – H
I I
H – C – OH H – C – OH
I I
H – C H – C –
I I
CH2OH CH2OH
- D glucose β – D glucose
CH3OH
Methyl
Alcohol

H OCH3 HCO H
C C
I I
H – C – OH H – C – OH
I I
HO – C – H HO – C – H +
H2O
I I
H – C – OH H – C – OH
I I
H – C H – C
I I
CH2OH CH2OH
3
Methyl - D methyl β – D
Glucose Glucose
Acetal inkage
is used for
both
Ketones
aldehyde

Cardiac Glycosides (Digoxin)
Drugs used in of CCF and
Cardiac arrythmias (AF)
Glycoside hydrolases (Glycosidases)
Catahyse the hydrolysis of glycosidic
linkage to release small sugars.
o cellulases used for degrading cellulose
to glucose.

Invertase for manufacturing of invert
sugar (Honey food industry).
Xylanases for removing hemicellulose
from paper pulp (paper and pulp
industry).

Carbohydrates

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