The present topic focus on carbohydrates which will be beneficial for pharma as well as science graduate students

1. PREPARED BY
Mr. V.M.Gaware
Asst. Prof
College of Pharmacy (For Women),
Chincholi Nashik

3. IMPORTANT POINTS TO REMEMBER IN
CARBOHYDRATES
1. Hydrates of Carbon C(H2O)
2. C:H:O 1:2:1
3. General Formula Cn(H2O)n
4. Value of n ≥ 3
5. Exceptions C2H4O2 : Acetic acid
C3H6O3: Lactic Acid
C5H10O4: Dioxyribose

4. Definition:
• Carbohydrates are defined as polyhydroxyaldehydes or ketones or
compounds which produce them on hydrolysis.
• The term sugar is applied to carbohydrates soluble in water and
sweet to taste. Examples

5. Functions:
• They are the most abundant dietary source of energy.
• They are precursors for many organic compounds i.e. fats and
amino acids.
• They participate in the structure of cell membrane and cellular
functions such as cell growth, adhesion and fertilization.

6. • They are structural components of many organisms which includes
fiber of plants ,exoskeleton of some insects and cell wall of
microorganisms.
• They also serve as the storage form of energy to meet the immediate
energy demands of the body.

7. Classification:
They are often referred to as saccharides.
They are mainly classified into three major groups:
1. Monosaccharide's
2. Oligosaccharide’s
3. Polysaccharide’s
• Mono and Oligo- saccharides are sweet in taste, crystalline in
nature and soluble in water.
• Polysaccharides are insoluble in cold water.

8. Carbohydrates
Monosaccharide's Oligosaccharides Polysaccharides
Aldoses : Glucose
Ketoses : Fructose
Disaccharides
Reducing Sugars:
Maltose, Lactose
Non reducing
Sugars: Sucrose
Trisaccharides
e.g. Raffinose
Homopolysacchrides
Starch
Heteropolysacchrides
Cellulose

9. MONOSACCHARIDES
• Monosaccharides (mono-one) are the simple sugar of
carbohydrates.
• General formula Cn(H2O)n
• They cannot be further hydrolyzed
• They are further divided into different categories depending
on the functional group and number of carbon atoms.
Aldoses Ketoses
The functional group is aldehyde (-HC=O)
e.g. Glyceraldehyde, Glucose
The functional group is keto (-C=O)
e.g. dihydroxyacetone, fructose

10. BASED ON THE NUMBER OF CARBON ATOMS
THEY ARE CLASSIFIED AS

11. OLIGOSACCHARIDES
• Oligosaccharides (oligo-few) contain 2-10 monosaccharide
molecules on hydrolysis.
• Based on the number of monosaccharide units present they
are subdivided to
Disaccharides
2 units of monosaccharide's
Trisaccharides
3 units of monosaccharide's
1. Reducing disaccharides with free aldehyde
or keto group e.g. maltose & lactose
2. Non-reducing disaccharides with no free
aldehyde or keto group e.g. sucrose
e.g. Raffinose

12. POLYSACCHARIDES
• Polysaccharides (poly-many) are polymers of monosaccharide
units with high molecular weight.
• They are usually tasteless (non-sugar) and are insoluble in
cold water.
• They are branched together by glycosidic linkage.
• They are further sub-divided into two types:
Homopolysacchrides
Single type of monosaccharide's
Heteropolysacchrides
Mixture of monosaccharide's
e.g. Starch, Dextrin's, Dextrans,
Inulin, Glycogen, Cellulose and
Chitin
e.g. Mucopolysaccharides, Agar and
Pectins, Glycoprotein's

13. MONOSACCHARIDES STRUCTURAL ASPECTS
Stereoisomerism:
Stereoisomer's are the compounds that have the same
structural formulae but differ in their spatial configuration and
the process is called Stereoisomerism

14. C
OH
CH OH
CH2OH
L - Glyceraldehyde
C
OH
COH H
CH2OH
D- Glyceraldehyde

15. D and L isomers
• The D & L isomers are mirror images of each other.
• The spatial orientation of –H & -OH groups on the carbon that
is adjacent to the terminal primary alcohol carbon determines
whether the sugar is D or L isomer.

16. C
OH
CH OH
COH H
CH OH
C OHH
CH2OH
D - Glucose
C
OH
CH OH
COH H
CH OH
C HOH
CH2OH
L - Glucose
• E.g. For glucose if the –OH group is on right side the sugar is of
D- series and if on left side its of L-series.

17. • It is assumed that the naturally occurring monosaccharide's in
mammalian tissues are mostly of D- configuration.
• The enzymes of cells is specific to metabolize D-series of
monosaccharide's.

18. OPTICALACTIVITY OF SUGARS
• Optical activity is important feature of compounds with
asymmetric carbon atom.
• When a beam of polarized light is passed through a solution of
optical isomer it will be rotated either to the right or left.
• The term dextrorotatory (D+) means rotate the plane of
polarized light to right side & levorotatory means to left side.
• An optical isomer may be designated as D (+), D (-), L (+) and L
(-) based on its structural relation with Glyceraldehyde.

19. RACEMIC MIXTURE
• If d and l isomers are present in equal concentration in a
solution it is known as racemic mixture or dl mixture.
• Racemic mixture does not exhibit any optical activity since the
dextro and levorotatory activities cancel each other.

20. EPIMERS
• If two monosaccharide's differ from each other in their
configuration around a single specific carbon (other than
anomeric) atom they are referred as epimers to each other.
• This interconversion of epimers is known as epimerization and
a group of enzymes is called epimerase.

21. C
OH
CH OH
COH H
CH OH
C OHH
CH2OH
D - Glucose
C
OH
CH OH
COH H
COH H
C OHH
CH2OH
D - Galactose
C
OH
COH H
COH H
CH OH
C OHH
CH2OH
D - Mannose
2
4 4
2
• E.g glucose & glactose are epimers of each other with regard to
carbon 4.
• That is they differ in arrangement of –OH group at C4
• Glucose and mannose are epimers at C2

22. ENANTIOMERS
• Enatiomers are a special type of stereoisomer's that are mirror
images of each other.
• They are designated as D & L-sugars.
• Majority of the sugars in higher animals are of D type.
C
OH
CH OH
COH H
CH OH
C OHH
CH2OH
D - Glucose
C
OH
CH OH
COH H
CH OH
C HOH
CH2OH
L - Glucose

23. • The term diasteremomers is used to represent the
stereoisomer's that are not mirror images of one another.

24. STRUCTURE OF GLUCOSE
• The hydroxyl group of monosaccharide's can react with
its own aldehyde or keto functional group to form
hemiacetal and hemiketal.
• Thus the aldehyde group of glucose at C1 reacts with
alcohol group at C5 to form two types of cyclic
hemiacetals namely alpha and beta.

27. PYRANOSE AND FURANOSE STRUCTURE
• Haworth projection formulae are depicted by 6
membered ring pyranose analogy with pyran or 5
membered ring furanose analogy to furan.
• This cyclic forms of glucose are known as glucopyranose
and fructofuranose respectively.

29. ANOMERS –MUTAROTATION
• The α and β cyclic forms of D-glucose are known as anomers.
• They differ from each other in the configuration only around
C1 known as anomeric carbon.
• In case of α anomer the –OH group held by anomeric carbon
is on the opposite side of the group –CH2OH and vice-versa
for β- anomer.
• The anomers differ in certain physical and chemical
properties.

31. MUTAROTATION
• The two anomers of D- glucose as any pair of
diasteremomers have different physical and chemical
properties.
• For e.g. the values of the specific optical rotation for α- D-
glucose and β- D-glucose are +112.20and + 18.70 respectively
in fresh water.
• In presence of alkali medium this optical rotation of α- D-
glucose decreases rapidly till the equilibrium is attained i.e.
+ 52.7 0.

32. • Mutarotation is defined as the change in the specific optical
rotation representing the interconversion of α and β forms
of D- glucose to an equilibrium mixture.
• α- D- glucose Equilibrium β- D-glucose
+112.20 +52.70 +18.70
• The equilibrium mixture contains 63% of beta anomer and
36% alpha anomer of glucose with 1% open chain form.

33. REACTIONS OF MONOSACCHARIDES
1. Tautomerization or enolization:
• The process of shifting a hydrogen atom from one carbon atom
to another to produce enediols is known as tautomerization.
• Sugars possessing anomeric carbon atom undergoes this process
in alkaline solutions.
• When glucose is kept in alkaline solution for several hours it
undergoes isomerization to form D- fructose and D- mannose
forming the common intermediate enediol.
• The enediols are highly reactive hence in alkaline solution sugars
are powerful reducing agents.

35. REDUCING PROPERTIES
• The sugars are classified as reducing or non-reducing.
• The reducing property is attributed to the free aldehyde or
keto group of anomeric carbon.
• The chemical tests used to identify the reducing action of
sugars includes:
 Benedicts test
 Fehling's test
 Barfoed’s test

36. • The enediol forms reduce cupric ions (Cu2+) of copper
sulphate to cuprous ions (Cu+) which forms a yellow ppt of
cuprous hydroxide or red ppt of cuprous oxide.
• The reducing property of sugars cannot help for specific
identification of any sugar hence they are consider as
general reactions.

38. OXIDATION
• Depending upon oxidizing agent the terminal aldehyde or
keto or the terminal alcohol or both the groups may be
oxidized.
1. Oxidation of aldehyde group CHO COOH results in
the formation of gluconic acid.
2. Under strong oxidation conditions both first and last carbon
atoms are simultaneously oxidized to form dicarboxylic acid
i.e glucuronic acid

39. REDUCTION
• When monosaccharide's are treated with sodium amalgam
the aldehyde or keto group is reduced to corresponding
alcohol
• e.g.
 D-Glucose --------- D-Sorbitol
 D-Galactose------- D-Dulcitol
 D-Mannose-------- D-Mannitol
 D-Fructose-------- D-Mannitol+D-Sorbitol
 D-Ribose----------- D-Ribitol
H C
R
O 2H
C
H
OHR
H

40. DEHYDRATION
• When monosaccharide's are treated with concentrated
sulfuric acid they undergoes dehydration with an
elimination of 3 water molecules.
• Thus hexoses gives hydroxymethyl furfural while pentoses
gives furfural on dehydration.

42. • These furfurals can condense with phenolic compounds
(alpha-naphthol) to form colored products basically
carried out in molish test.
• In case of Oligo and polysaccharides they are first
hydrolyzed to monosaccharide's by acid followed by
dehydration.

43. OSAZONE FORMATION
• Phenylhydrazine in acetic acid when boiled with reducing
sugars forms osazones.
• The first two carbons are important and are involved in
osazones formation.
• The sugars that differ in their configuration on these two
carbons give the same type of osazones as difference is
identified by binding with Phenylhydrazine.
• Thus glucose, fructose and mannose gives the same type of
osazones (needle shape).
• Reducing disaccharides also give osazones maltose
sunflower shape and lactose powder puff shape.

46. FORMATION OF ESTERS
• The alcoholic groups of monosaccharide's may be
esterified by non-enzymatic or enzymatic reactions.
• Esterification of carbohydrate with phosphoric acid is
common reaction in metabolism.
• E.g. Glucose 6-phosphate and glucose 1-phosphate.
• ATP is donated in ester formation by phosphate group.

47. GLYCOSIDES
• Glycosides are formed when the hemiacetal or hemiketal
hdroxyl group of anomeric carbon reacts with a hydroxyl
group of another carbohydrates or non-carbohydrates.
• The bond so formed is known as glycosidic bond and the
non-carbohydrate group is called aglycone.
• The monosaccharides are held together by glycosidic
bonds to form di, oligo or polysaccharides.

48. NAMING OF GLYCOSIDIC BOND
• The nomenclature of glycosidic bonds is based on linkages
between the carbon atoms and the status of anomeric carbon (α
or β).
• E.g. Lactose is formed by a bond between C1 of β- galactose
and C4- of glucose hence named as β (1 4) glycosidic bonds.

49. DISACCHARIDES
• The disaccharides consists of two monosaccharide's units
(similar or dissimilar) held together by glycosidic bond.
• They are crystalline, water soluble and sweet to taste.
• They are classified in two types:
1. Reducing disaccharides with free aldehyde or keto group
e.g. maltose and lactose.
2. Non-reducing with no free aldehyde or keto group.
e.g. sucrose and trehalose.

50. MALTOSE
• Maltose is composed of two alpha-D-glucose units held together
by α (1 ---- 4) glycoside bond.
• The free aldehyde group is present on C1 of second glucose and it
shows sunflower shaped osazone.
• It can be hydrolyzed by dilute acid or enzyme maltase to give two
molecules of α-D-glucose.
• In isomaltase the glucose units are held together by α (1 ---- 6)
glycosidic linkage

51. LACTOSE
• It is more commonly known as milk sugar since it is the
disaccharide found in milk.
• It is composed of β- D- galactose and β- D- glucose held together
by β (1----- 4) glycosidic bond.
• The anomeric carbon of C1 of glucose is free hence they reducing
properties and forms osazone i.e powder puff shape.
• It is hydrolyzed by intestinal enzyme lactase to glucose and
galactose.

52. SUCROSE
• It is also called cane sugar mostly produced by sugarcane and
sugar beets.
• It is made up of α-D-glucose and β- D-fructose held together by
glycosidic bond (α1 ----- β2 ) between C1 of α-D-glucose and C2 of
β- D-fructose.
• It does not have free aldehyde or keto group as it is involved in
glycosidic bond, hence are non-reducing and cannot form
osazones.
• It is major carbohydrate produced in photosynthesis.
• It has distinct advantages over other sugar as it is protected from
oxidative attacks as both functional groups aldehyde and keto
are held together.

53. INVERSION OF SUCROSE
• Sucrose as such is dextrorotatory but when hydrolyzed it
becomes levorotatory.
• This phenomenon of change in optical rotation is termed as
inversion.

55. POLYSACCHARIDES
• It consists of repeat units of monosaccharide's or their derivatives held
together by glycosidic bond.
• They are classified in two types:
1. Homopolysacchrides:
• Which on hydrolysis yield only single type of monosaccharide’s. e.g
starch, dextrins, Inulin, glycogen
• Thus glucans are polymers of glucose and fructosans are polymers
of fructose.
2. Heteropolysacchrides: on hydrolysis yield a mixture of few
monosaccharides or their derivatives.
e.g. Mucopolysacchrides: Hyaluronic acid, chondroitin sulfates, heparin.
Glycoproteins