1. Carbohydrates are classified as monosaccharides, disaccharides, oligosaccharides, or polysaccharides depending on their size. Monosaccharides include glucose and fructose. 2. Important carbohydrates include starch, glycogen, cellulose, and dietary sugars like sucrose, lactose, and glucose. Starch is the storage form of carbohydrates in plants while glycogen serves this function in animals. 3. Carbohydrates have several important functions in the body including energy storage, structural roles, and serving as precursors for other biomolecules. They exhibit properties like being water-soluble and capable of undergoing chemical reactions like reduction and oxidation.

1. ChemistryChemistry
ofof
CarbohydratesCarbohydrates
Dr. Ifat Ara Begum
Associate Professor
Dept of Biochemistry
Dhaka Medical College
Dhaka

2. DefinitionDefinition
 Aldehyde (-CHO) or ketone (-C=O)
derivatives of polyhydric alcohol or the
compounds which produce these derivatives
on hydrolysis
2

3. ClassificationClassification
3
Monosaccharid
e
Disacch. Oligosacch. Polysacch.
The simplest form
of carbohydrates
that can’t be
hydrolyzed into
further simpler
form
Carbohydrate
produced by
condensation
of 2
monosacch.
units by
glycosidic
bond
Carbohydrate
produced by
condensation of
3 - 10
monosacch.
units by
glycosidic bond
Polymer of
monosacch
composed of
>10
monosacch.
units
connected by
glycosidic
bondExample:
Glucose,
Fructose ,
Galactose etc
Example:
Maltose,
Sucrose,
Lactose
Example:
Maltotriose,
Raffinose
Example:
Starch,
Cellulose,
Glycogen

4. 4

5. 5
Dietary carbohydrates include:
 Starch : Rice, potato, wheat
etc
 Lactose: Milk & milk products
 Sucrose: Cane sugar
 Cellulose: Vegetables, fruits

6. 1. Monosaccharide / Simple sugar1. Monosaccharide / Simple sugar
 Three to nine carbon compounds
 Serves as building block of all carbohydrates
 General formula: Cn (H2O)n
6

7. Classification of monosaccharides based on no. ofClassification of monosaccharides based on no. of
carbon & the functional group they containcarbon & the functional group they contain
7
Generic name Number
of
carbon
Aldose
(-CHO)
Ketose
(-C=O)
Triose 3 Glyceraldehyde Dihydroxy
acetone
Tetrose 4 Erythrose Erythrulose
Pentose 5 Ribose Ribulose
Hexose 6 Glucose Fructose

8. 8
Pentoses & hexoses are the most
important monosaccharides

9. In aldoses, the aldehyde functional group : 1st
carbon
In ketoses, ketone functional group: 2nd
carbon
9

10.  Primary alcohol group (CH2OH) of
monosaccharides is attached with terminal
carbon i.e. 6th
C for hexose & so on
10

11.  Penultimate carbon:
• It means second to last carbon. i.e.
the carbon adjacent to primary alcohol carbon
e.g. 5th
carbon for hexose & so on
11

12. In carbohydrate, orientation of –H & -OH
group around this carbon determines whether
the sugar is of D-series or L-series.
12

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Importance (Functions)
of Glucose
 Acts as :
 Chief source of energy
Storage form of energy (as
glycogen)
 Protein & fat sparer
 Precursor for synthesis of
lipids, AA, glycoprotein &
proteoglycans
 Helps in :
 Protein & Fat metabolism
 Nucleic acid synthesis (by
providing ribose)
 Constitute
structural component
of :
 Biological
membrane
Intracellular ground
substance
 Biological lubricant
 Involved in
detoxification of toxic
substance in liver by
providing glucuronic
acid

16. 2. Disaccharide2. Disaccharide
 Here, two molecules of same / different
monosaccharides are produced on hydrolysis
 General formula: Cn (H2O)n-1
16

17. 17
Disaccharid
e
Monosaccharide Example
Maltose Glucose + Glucose
Lactose Glucose +
Galactose
Milk sugar
Sucrose Glucose +
Fructose
Table sugar

18. 3. Oligosaccharide3. Oligosaccharide
 Example:
Maltotriose, Raffinose, Blood group
substance etc
18

19. 4. Polysaccharide4. Polysaccharide
 Also called glycans
 General formula: (C6H10O5)n
19

20. Two types of polysaccharidesTwo types of polysaccharides
20
Homo polysaccharide /
Homoglycan
 Polymer of similar type of
monosaccharide units,
connected by glycosidic
bond.
 Example:
 Starch
 Glycogen
 Cellulose etc
Hetero
polysaccharide /
Heteroglycan
 Polymer of different
types of monosaccharide
units / their derivatives,
connected by glycosidic
bond.
 Example:
 MPS or GAG
 Carbohydrate part of
glycoprotein

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Homo
Polysaccharide

22. 22
Homo
polysacch
Mono-
mer unit
Source Other features
Starch:
Storage form
of carboh. in
plant
2 types
a) Amylose
b)Amylopectin
α-D-
glucose
Entirely
plant
Amylose: Straight
chain structure,
Sparingly water
soluble
Amylopectin:
Branched chain
structure, Water
insolubleGlycogen/
Animal starch:
Storage form
of carboh. in
animal &
human
α-D-
glucose
Entirely
animal:
Liver
glycogen,
Muscle
glycogen
Resembles
Amylopectin:
Branched chain
structure, no. of
branches
>Amylopectin.

23. 23
Homo
polysacch
Mono-
mer
unit
Source Other features
Dextrin α-D-
glucose
Produced
by partial
break down
(hydrolysis)
of starch
Glycosidic bonds in
starch are randomly
broken down by α-
amylase & produces
these oligosacch.
fragments
Dextran α-D-
glucose
Formed by
microbes
(bacteria,
yeast etc)
Branched structure,
non digestible,
colloidal in nature.
Clinically used as
plasma expander to
prevent
Hypovolemic shock
during major
surgery / fluid-losing

24. 24
Homo
polysacch
Mono-
mer
unit
Source Other features
Cellulose β-D-
glucose
Plant
source like
vegetables,
fruits etc
Straight chain
structure, Non
digestible in human,
so gives no energy
Inulin Fructose Onion,
garlic etc
Water soluble, LMW,
used for
measurement of
GFR.
No dietary
importance

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Importance (Functions) of Cellulose
Importance:
 Maintains regular bowel
habit , prevents constipation
 Facilitates cholesterol
excretion, keeps serum
cholesterol low & reduces
risk of CAD
 Prevents risk of
 obesity
 DM
 Colonic cancer
Disadvantage:
 Prevents intestinal
absorption of
minerals

26. Amylose vs. AmylopectinAmylose vs. Amylopectin
26
Amylose Amylopectin
Represent 10 – 20% of
starch
Represent 80 – 90% of
starch
LMW HMW
Has 200 – 1000 glucose
molecules
Has few thousands of
glucose molecules
Sparingly water soluble Water insoluble
Straight chain, unbranched Highly branched
Gives blue color with dilute
iodine solution
Gives reddish violet color
with dilute iodine solution

27. Glycogen vs. StarchGlycogen vs. Starch
27
Starch Glycogen
Plant source Animal source
Amylose: Unbranched
Amylopectin: Less branched
Highly branched structure
MW: About 5 lac MW: 10 – 40 lac
Gives reddish violet color
with iodine solution
Gives deep red color with
iodine solution
Main dietary carbohydrate in
human
Storage form of
carbohydrate in human

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Hetero
polysaccharides

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GAGs / MPS
 Long chain hetero
polysaccharide, mostly
unbranched
 Consists of repeating
disaccharides made of
 amino sugar e.g.
Glucosamine
&
 acidic sugar e.g.
glucuronic acid
 Contain uronic acid
(glucuronic acid) but no
sialic acid
Glycoprotein
 Short chain hetero
polysaccharide, mostly
branched
 Consists of
 hexoses & their
acetylated amino
derivatives
 pentoses
&
 sialic acid
 Contain sialic acid but no
uronic acid

30. 30
Types of MPS /
GAGs
Possible site
Hyaluronic acid Connective tissues, synovial
fluid etc
Chondroitin SO4 - A Cartilage, bone, tendon etc
Chondroitin SO4 – B
(Dermatan SO4)
Skin, blood vessels etc
Chondroitin SO4 - C Cartilage, bone, tendon etc
Keratan SO4 Cartilage, cornea etc
Heparan SO4 Cell surface, basement
membrane
Heparin Mast cells

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Importance (Functions)
of GAGs / MPS
 Component of
extracellular matrix,
synovial fluid, vitreous
humor, mucus etc
 Act as:
 Biological lubricant
providing protection
against microbial injury /
invasion
Importance (Functions)
of Glycoprotein
 Component of
extracellular matrix
 Act as :
 Biological lubricant
providing protection
against microbial injury /
invasion
 Cell surface receptor
 cell surface antigen
 Cellular recognition &
cell to cell interaction

32. Properties of CarbohydratesProperties of Carbohydrates
32
Physical
properties
 Water soluble
 Crystalline
 Sweet in taste
 Optically active
Chemical properties
 Reducing agent in alkaline
media
 Oxidizes to sugar acid
 Reduces to alcohol
 Formation of :
 Osazone with phenyl
hydrazine
 Glycoside by condensation
with alcoholic group of
another substance

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35. What is isomerism?What is isomerism?
It is the process of formation of isomers
Isomers:
Substances having same molecular /
chemical formula
but
 different structures or
 different spatial configuration around 1/more
carbon atom
35

36. 36
1. Structural isomers:
Different in structural
form
2. Stereo / Space isomer:
Different in
arrangement of atoms / groups
around 1/more carbons in
relation to space
a) Geometric isomer: Restricted rotation of C = C double
bonds. e.g. Cis / Trans configuration
b) Optical isomer: Chiral centre & diff. optical activity.
e.g. D-L isomerism, α-β anomerism

37. Sucrose : Invert sugarSucrose : Invert sugar
37
Dextrorotatory optical character of sucrose on
hydrolysis is inverted to levorotatory
character.

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