Carbohydrates are the most abundant biomolecules on Earth. They are classified as monosaccharides, oligosaccharides, or polysaccharides depending on their complexity. Monosaccharides include simple sugars like glucose and fructose. Oligosaccharides contain 2-10 monosaccharide units and include disaccharides like sucrose, lactose, and maltose. Polysaccharides are long chains of monosaccharides and include starch, cellulose, and glycogen. Carbohydrates serve important functions like energy storage, structure, and participating in biological processes as components of other biomolecules.

1. CARBOHYDRATES
Chemistry and Functions
Ms. Jigisha Pancholi
Head
Dept. of Biochemistry & Microbiology
Indian Institute of Ayurvedic
Pharmaceutical Sciences
Gujarat Ayurved University
Jamnagar

2. Introduction
 Most abundant biomolecule on Earth.
 Each year, photosynthesis converts more than 100 billion
metric CO2 and H2O into cellulose and other plant
products!!
 Optically active compounds with polyhydroxy aldehydes
or ketones.
 Hydrates of carbon and contain carbon, hydrogen and
oxygen in the ratio 1:2:1.
 General formula Cx (H2O)y.

3. Classification
 Depending upon the composition and complexity,
they are divided into three groups:
 Monosaccharides
 Oligosaccharides
 Polysaccharides

4. Monosaccharides
 Cannot be further hydrolysed into simple sugars.
 Simple sugars, sweet, water soluble and crystalline
in nature.
 Contain 3 to 9 carbon atoms.
 Represented as (CH2O)n.

5.  Depending upon the functional groups, there are two
types:

6. Examples
Number of
carbon atoms
Generic name Aldoses Ketoses
3 Triose Glyceraldehyde Dihydroxyacetone
4 Tetrose Erythrose Erythrulose
5 Pentose Arabinose, Xylose,
Ribose
Xylulose,
Ribulose
6 Hexose Glucose, Galactose,
Mannose
Fructose
7 Heptose Glucoheptose Sedoheptulose

7. Structures
 Triose
aldose ketose

8.  Tetrose
aldose ketose

9.  Pentoses
aldose ketose

10.  Hexoses
aldose ketose

11. Oligosaccharides
 Hydrolysable polymers of monosacharides
 Contain 2- 10 molecules of simple sugars
 Joined by glycosidic bond
 Alpha bond or beta bond

12. Types and Examples
 Disaccharides : 2 monosaccharide units
Maltose = Glucose + Glucose
Alpha (1->4) bond

13.  Lactose = Galactose + Glucose
Beta (1->4)bond

14.  Sucrose = Glucose + Fructose
Alpha (1 ->2) bond

15. Reducing and Non- reducing sugars
 Reducing Sugar : Sugars with free aldehyde and
ketone groups.
Example: Maltose, lactose.
 Non- reducing Sugar: Sugars with NO free aldehyde
and ketone groups.
Example: Sucrose, trehalose.

16. Disaccharide Source Structure Bond Reducing
property
Sucrose cane sugar
beat sugar
table sugar
α-D-glucose +
β-D-Fructose
α-1,2
glycosidic
bond.
Non reducing
sugar
Lactose milk sugar β-D-galactose
+ α-D-glucose
β-1,4
glycosidic
bond
Reducing
sugar
Maltose Malt sugar 2 molecules of
α-D-glucose
α-1,4
glycosidic
bond.
Reducing
sugar

17. Other Oligosaccharides
 Trisaccharides: 3 monosaccharide units.
Ex: Raffinose = Fructose+ Glucose + Galactose
Gentianose = Fructose + Glucose + Glucose
 Tetrasaccharides: 4 monosaccharide units.
Ex: Stachyose = Galactose + Galactose + Glucose+
Fructose
 Pentasaccharides: 5 monosaccharide units.
Ex: Verbascose = Gal+ Gal+ Gal+ Glu +Fru

18. Polysaccharides
 Long chain of monomers of more than 10 subunits
 General formula: (C6H10 O5)n
 Can be linear or branched
 Two types:
Homopolysaccharides: made up of same monomers.
Example- starch, glycogen, cellulose, inulin, dextrin,
dextran.
Heteropolysaccharides: made up of different
monomers.
Example: heparin, agar, hyaluronic acid, chondroitin
sulphate.

20. Starch
• Main carbohydrate in food.
• Present in plants, not found in animals.
• Storage form of carbohydrates in plants.
• Sources : potatoes, cereals (rice & wheat) etc.
• Consists of amylose & amylopectin

21. Starch
10-20%
Soluble
80-90%
Insoluble
Amylose Amylopectin
•Made up of α-glucose
•Straight chain
•α-1,4 glycosidic bonds
•Made up of α-glucose
•Branched chain
•alpha-1,6 linkage

23. Glycogen
 Major storage form of carbohydrates in animals
 Stored in muscle and liver.
 Excess carbohydrates are deposited as glycogen.
• Formed of α-glucose units linked by α-1,4 glycosidic bonds
with many branches at α-1,6 glycosidic bonds.
• Innermost core of glycogen contains a primary protein called
Glycogenin.
• Glycogen is more branched and more compact than
amylopectin.

24. Structure of glycogen

25. Cellulose
 It is the supporting tissue of plants.
 Cellulose constitutes 99% of cotton, 50 % of wood & is
the most abundant organic material in nature.
 It is made up of glucose units combined with beta-1,4
linkages.
 It has a straight line structure, with no branching points.
 Beta-1, 4 bridges are hydrolysed by the enzymes
CELLOBIASE which is absent in animal & human
digestive system, hence cannot be digested.

26. Inulin
 It is a long chain homoglycan composed of D-fructose
units with repeating beta-1,2 linkages.
 It is the reserve carbohydrate present in various bulbs &
tubers such as onion, garlic.
 It is clinically used to find renal clearance value &
glomerular filtration rate.

27. Dextran
 These are highly branched homopolymers of glucose units
with 1-6, 1-4 & 1-3 linkages.
 They are produced by microorganisms & molecular
weight 1 million to 4 millions.
 They will not easily go out of the vascular compartment.
 They are used for intravenous infusion as plasma volume
expander for treatment of hypovolemic shock.

28. Chitin
 It is present in exoskeletons of crustacea & insects.
 It is composed of units N-acetyl-glucosamine with beta-
1, 4 glycosidic linkages.

30. Agar
 It is prepared from sea weed
 It contains galactose, glucose & other sugars
 It is used:
 to culture bacterial colonies
 a supporting medium for immuno diffusion & immuno
eletrophoresis
 agarose is made up from agar and is used as matrix for
electrophoresis

31. Hyaluronic acid
 Repeating disaccharide units- N-Acetyl-glucosamine and
beta-1, 4-glucuronic acid
It serves as a lubricant in joint cavities

32. Heparin
 Repeating disaccharide units-
sulphated glucosamine + alpha-1, 4-L-iduronic acid

33.  It is the natural anticoagulant
 It is widely used when taking blood in vitro for clinical
studies
 Also used in vivo in suspected thrombo embolic
conditions to prevent intravascular coagulation

34. PROPERTIES

35. Stereoisomer
 Compounds having same chemical formula , but differing
in spatial/structural configuration are known as
stereoisomers.
 Asymmetric carbon means that four different groups are
attached to the same carbon.

36.  The number of possible stereoisomers depends on the
number of asymmetric carbon atoms.
 Which is known by the formula 2n , where n is the
number of asymmetric carbon atoms.
 The reference molecule is glyceraldehyde which has a
single asymmetric carbon atom.

37. Reference sugar

38. Enantiomers
 Structures that are mirror images of each other, which are non
superimposable.
 These mirror images are called Enantiomers
 Two members of the pair are designated as a D- and an L-sugar
.
 Two compounds that are enantiomers of each other have
the same physical properties, except for the direction in
which they rotate polarized light.
 By humans, only D-sugars can be metabolized.

40. Optical activity
 The presence of asymmetrical carbon atom causes optical
activity.
 When a beam of plane-polarized light is passed through a
solution of carbohydrates, it will rotate the light either to right
or to left.
 Note that the D- and L- notation has no bearing with the optical
activity.

41.  Depending on the rotation, molecules are called
dextrorotatory(+,d) or levorotatory(-,l).
 Thus D-glucose is dextrorotatory but D-fructose is
levorotatory.
 Equimolecular mixture of optical isomers has no net rotation
(Racemic Mixture)

42. Epimers
 When sugars are different from one another, only in
configuration with regard to a single carbon atom, they are
called epimers.
 For example, glucose and mannose are an epimeric pair
which differ only with respect to C2. Similarly, galactose
is the 4th epimer of glucose.

44. Cyclization of sugars
 Less than 1% of the monosaccharides exists in the open-chain
(acyclic) form.
 Predominantly found in a ring (cyclic) form, for example,
glucopyranose.

45. Anomerism
 Cyclization creates an anomeric carbon
 Generating the α and β configurations of the sugar
 For example,
 α-D- glucopyranose
 β-D- glucopyranose
 In the α configuration, the OH on the anomeric C (1st carbon)
projects to the same side as the ring.

46.  Enzymes are able to distinguish between these two structures
and use one or the other preferentially.
 For example, glycogen is synthesized from α-D-glucopyranose,
whereas cellulose is synthesized from β-D-glucopyranose.

47. Mutarotation
 When D-glucose is crystallized at room temperature (37˚C) ,
and a fresh solution is prepared, its specific rotation of
polarized light is +112˚ ; but after 12-18 hours it changes to
+52.5˚.
 If initial crystallization is taking place at 98˚C and then
solubilised, the specific rotation is found to be +19˚, which also
changes to +52.5˚ within a few hours.
 This change in rotation with time is called mutarotation.

48.  This is explained by the fact that D-glucose has two
anomers, alpha and beta varieties.
 alpha-D-glucose has specific rotation of +112˚ and beta-
D-glucose has +19˚.
 Both undergo mutarotation and at equilibrium one-third
molecules are alpha type and 2/3rd are beta variety to get
the specific rotation of +52.5˚.

49. FUNCTIONS

50.  Source of energy
 Storage of energy

51.  Structural units
 Glucose as chief physiological sugar

52.  Heparin is a natural anticoagulant
 Blood groups

53.  Hyaluronic acid lubricates joints
 Ribose sugar is a part of DNA and RNA

54.  Dextrin is used in postage stamps
 Fructose is used in beverages

55.  Sucrose is the table sugar
 Cellulose is a part of paper and cloth

56.  Exopolysaccharides used in sauce to produce
pseudo plasticity
 Inulin used to measure GFR

57.  Present in cells as glycoproteins and glycolipids
 Agar used as gelling agent and in constipation

58.  Monosaccharides and oligosaccharides are bound to
lipids and proteins to form the conjugates and are
present on the cell surfaces, important in cell- cell
recognition, cell- cell adhesion and receptor binding
to ligand.

59.  D- Ribose is the constituent certain coenzymes like
FAD, NADH, NADPH and FMN.
 D- glucuronic acid is formed from glucose in the liver.
It is a constituent of certain heteropolysaccharides
and conjugates with toxic substances, drugs,
hormones and bilirubin and helps their removal from
body.

60.  Glycosides are found in many drugs and spices. Eg.,
Glucovanillin gives vanilla flavor, streptomycin is an
antibiotic and cardiac glycosides like digitoxin
stimulate heart muscles.
 Sucrose, if introduced parenterally cannot be
utilized, but it can change the osmotic condition of
the blood and cause a flow of water from the tissues
into the blood. It can be used to treat swelling.

61.  Cellulose cannot be digested by the body and acts
as roughage.
 Dextran is used as a lubricant as in eye drops.

62.  Hyaluronic acid is present in high concentration in
embryonic tissues and is considered to play an
important role in cell migration during
morphogenesis and wound repair.
 Dermatan sulphate is important to maintain the
overall shape of the eye.

63.  People take hyaluronic acid for various joint
disorders, including osteoarthritis.
 Some people apply hyaluronic acid to the skin for
healing wounds, burns, and skin ulcers.

64.  Hyaluronic acid is a common ingredient in skin-care
products as moisturizers and anti ageing component.
 Hyaluronic acid is also used as a lip filler in plastic
surgery.

65. Multiple Choice Questions
 Which of these is not made up of aldohexose
subunits?
A. Sucrose
B. Starch
C. Glycogen
D. Inulin
 Reducing sugars possess:
A. Aldehyde group
B. Ketone group
C. Carboxylic group
D. Either A or B

66. Multiple Choice Questions
 Lactose is present in:
A. Sugarcane
B. Fruits
C. Milk
D. Both B and C
 Which of the following is a commercial
polysaccharide?
A. Keratin sulphate
B. Hyaluronic acid
C. Agar
D. Chondroitin sulphate

67. Multiple Choice Questions
 Reserve food material in plant cell is:
A. Starch
B. Glycogen
C. Cellulose
D. Pectin
 Which of these is 2000 times sweeter than sucrose?
A. Fructose
B. Glucose
C. Monellin
D. Aspartame

68. Multiple Choice Questions
 Glucose level in the body is maintained by:
A. Kidney
B. Liver
C. Spleen
D. Intestine
 In the milk of mammals, the disaccharide present is:
A. Glucose
B. Fructose
C. Galactose
D. Lactose

69. Multiple Choice Questions
 Alpha 1-4 linkage is found in :
A. Starch
B. Cellulose
C. Peptidoglycan
D. Amino acids
 In sugarcane and beet, the storage product is:
A. Maltose
B. Sucrose
C. Lactose
D. Isomaltose

70. Multiple Choice Questions
 One molecule of glucose and galactose forms:
A. Maltose
B. Sucrose
C. Lactose
D. Dextrin
 Which of these are used in producing shatter proof
glass?
A. Cellulose nitrate
B. Cellulose acetate
C, Carboxymethyl cellulose
D. Cellulose

71. Multiple Choice Questions
 Amylose, amylopectin and glycogen has:
A. Beta glucose
B. Alpha glucose
C. A and B glucose
D. Xylulose
 Cancer causing sugar is:
A. Sucrose
B. Lactose
C. Saccharin
D. Inulin

72. Multiple Choice Questions
 A disaccharide that gives two units of glucose upon
hydrolysis is :
A. Sucrose
B. Maltose
C. Lactose
D. None of the above
 Carbohydrates are formed by joining together of
sugar units through:
A. Glycosidic bond
B. Peptide bond
C. Ester bond
D. Covalent bond

73. Multiple Choice Questions
 Mucilages are:
A. Proteins
B. Polysaccharides
C. Lipids
D. Glycolipids
 Macromolecule chitin is:
A. Phosphorus containing polysaccharide
B. Sulphur containing polysaccharide
C. Simple polysaccharide
D. Nitrogen containing polysaccharide

74. Multiple Choice Questions
 Which of these given properties of starch make it
useful as a storage material?
A. Easily translocated
B. Chemically non reactive
C. Easily digested by animals
D. Osmotically inactive
E. Synthesised during photosynthesis
a. A and C
b. B and D
c. B and C
d. A.C and E

75. Multiple Choice Questions
 Most common monomer of carbohydrate is:
A. Maltose
B. Glucose
C. Fructose
D. Sucrose
 Which of these glycosidic bonds is found in sucrose?
A. Alpha 1-4
B. Beta 1-4
C. Alpha 1- 2
D. Beta 1-2

76. Multiple Choice Questions
 Which is a reducing sugar?
A. Cellulose
B. Starch
C. Sucrose
D. Maltose
 Chitin occurs in the walls of:
A. Algae
B. Bacteria
C. Fungi
D. Yeast

77. Multiple Choice Questions
 In plants inulin and pectin are:
A. Reserved material
B. Wastes
C. Excretory material
D. Insect attracting material
 Sugar present in DNA is:
A. Dextrose
B. Ribose
C. Ribulose
D. Deoxyribose