0carbohydrates. ppt

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1. CARBOHYDRATES

2. Definition of carbohydrates
Carbohydrates may be defined as
polyhydroxyaldehydes or ketones or
compounds which produce them on
hydrolysis.
They are most abundant organic molecules in
nature
They are primarily composed of elements
carbon, hydrogen and oxygen.
The name of carbohydrates literally means
‘hydrates of carbon’

3. Functions of Carbohydrates
Abundant dietary source of energy(4 Cal/g)
Precursors for many organic compounds(fats,
amino acids)
Participate (as glycoproteins & glycolipids) in
the structure of cell membrane(glycocalyx) &
cellular functions
Structural components (fiber in plants,
exoskeleton in insects etc)
Storage form energy(glycogen) to meet
immediate demand

4. Carbohydrates-
widely distributed in plants and animals;
having important structural and metabolic roles.
In plants-
glucose synthesized from carbon dioxide
and water by photosynthesis and stored as
starch or converted to the cellulose of the plant
framework.
In animals-
can synthesize carbohydrate from lipid
glycerol and amino acids, but most animal
carbohydrate is derived ultimately from plants.

5. CLASSIFICATION OF CARBOHYDRATESCLASSIFICATION OF CARBOHYDRATES
•Carbohydrates are often referred to as sachharides.
•They are broadly classified into 3 major groups:
1.Monosaccharides,
2.Oligosaccharides and
3.Polysaccharides
•This categorization is done based on sugar units

6. (1) Monosaccharides – simpler unit of
carbohydrate eg.glucose, fructose, sucrose
etc…
Mono- one; often refer to as simple sugar
General formula C
n
(H2O)
n
; cannot be hydrolysed
further
Based on different functional group and number of
carbon atoms, divided into different categories:
oAldoses: When functional group is aldehyde;
e.g glyceraldehyde, glucose
oKetoses: when functional group is keto; e.g
dihydroxyacetone, fructose
CLASSIFICATION OF CARBOHYDRATESCLASSIFICATION OF CARBOHYDRATES

7. Empirical formula-(C-H
2O)
n .literally ‘ CARBON HYDRATE’
MONOSACHARIDESMONOSACHARIDES

8. Structure of a simple aldose and a simple ketose

9. 2)Disaccharides - condensation products of two
monosaccharide units e.g. maltose and sucrose.
3)Oligosaccharides - condensation products of three
to ten monosaccharides e.g. maltotriose, raffinose
•Oligosaccharides with more than 3 monosaccharides
units are not usually digested by human enzymes
4)Polysaccharides - condensation products of more
than ten monosaccharide units e.g. starch, glycogen,
cellulose, dextrin etc, which may be linear or
branched polymers.

10. Mono and oligosaccharides are sweet to
taste, crystalline in character and soluble in
water and hence they are called as sugars.
Polysaccharides are tasteless(non-sugars)
and form colloids with water.

11. Stereoisomerism: An important character of
monosaccharides. They are compounds that have the
same structural formulae but differ in their spatial
configuration.
A carbon can be said to be asymmetric when attached to
four different atoms or groups. The number of asymmetric
carbon atoms(n) determines the possible isomers of a
given compound which is equal to 2
n
.
Glucose has 4 asymmetric carbons and thus has 16
isomers.

12. D and L isomerism: the D form or of its mirror image L form
(enantiomers) is determined by it spatial relationship to the parent
compound of the carbohydrates- Glyceraldehyde.
Tetroses, pentoses,
hexoses having
multiple asymetric
carbons exist as
diastreoisomers-
isomers that are not
mirror images of each
other.

13. Optical activity occurs due to asymmetric carbon
atoms (chiral carbon): those bonded to four
different atoms or groups of atoms
When a beam of plane-polarized light is passed
through a solution of an optical isomer, it will be
rotated either to the right, dextrorotatory (+); or to
the left, levorotatory (−).
When equal amounts of D and L isomer - no optical
activity – mixture is called racemic mixture .
OPTICAL ACTIVITY

15. Epimers:
Isomers differing as a result of variations in
configuration of the -OH and -H on carbon atoms 2, 3, and 4
of glucose

e.g. mannose and galactose, formed by epimerization at
carbons 2 and 4, respectively

17. Glucose - the most important carbohydrate:
 the major metabolic fuel of mammals
 the precursor for synthesis of other carbohydrates
in the body, including
a universal fuel of the fetus.
glycogen for storage;
ribose and deoxyribose in nucleic acids;
galactose in lactose of milk,
in glycolipids, in combination with protein in
glycoproteins
Diseases associated with carbohydrate metabolism -
diabetes mellitus, glucosuria, glycogen storage diseases,
and lactose intolerance.

18. BIOMEDICALLY, GLUCOSE IS
THE MOST IMPORTANT
MONOSACCHARIDE
A- Fischer projections- H and
OH groups attached to the carbon
atoms in a straight chain.
B- Haworth projections- if the
molecule is viewed from the side
and above the plane of the ring. By
convention, bonds nearest to the
viewer are bold and thickened.
C- Chair conformation: The six-
member ring containing one oxygen
atom is in the form of a chair

19. Pyranose and furanose ring structures: The stable
ring structures of monosaccharides are similar to the ring
structures of either pyran (a six-membered ring) or furan (a 5-
membered ring) For glucose in solution, > 99% is in the
pyranose form.

20. Pyranose and furanose forms of fructose

21. ANOMERIC FORMS:
(α and β anomers)
hemiacetal - formed by
combination of an aldehyde
and an alcohol group.
Similarly the ring structure
of a ketose is a hemiketal.
Crystalline glucose is
α-D-glucopyranose.
The cyclic structure is retained
in solution, but isomerism occurs
about position 1, the carbonyl or
anomeric carbon atom, to give a
mixture of α-glucopyranose (38%)
and β-glucopyranose (62%).

22. REACTIONS OF MONOSACCHARIDES

23. Oxidation reactions
Aldoses may be oxidized to 3 types of acids
Aldonic acids: aldehyde group is converted to a
carboxyl group ( glucose – gluconic acid)
Uronic acids: aldehyde is left intact and primary alcohol
at the other end is oxidized to COOH

Glucose --- glucuronic acid

Galactose --- galacturonic acid
Saccharic acids (glycaric acids) – oxidation at both
ends of monosaccharide)

Glucose ---- saccharic acid

Galactose --- mucic acid

Mannose --- mannaric acid

24. Reduction reactions
either done catalytically (hydrogen and a
catalyst) or enzymatically
the resultant product is a polyol or sugar
alcohol
glucose form sorbitol
mannose forms mannitol
fructose forms a mixture of mannitol and
sorbitol

25. Trioses of physiological importance :
- both D-glyceraldehyde and dihydroxyacetone
(in phosphate esters form)-intermediate in
glycolysis

Tetroses of physiological importance:
- erythrose-4-P ; an intermediate in HMP shunt
Some important carbohydrates

26. Pentoses of physiological importance

27. Hexoses of physiological importance

28. Sugars as reducing agents-
Oxidation of the anomeric carbon of glucose and other
sugars is the basis for Fehling’s reaction. The cuprous ion (Cu)
produced under alkaline conditions forms a red cuprous oxide
precipitate.
In the hemiacetal (ring) form, C-1 of glucose cannot be oxidized by
Cu
2+
. However, the open-chain form is in equilibrium with the ring
form, and eventually the oxidation reaction goes to completion.

29. Disacharides
Disacharides are the molecules which consist
of two monosacharaides units held together
by a glycosidic bond
These are of two types:
Reducing disacharides (having free aldehyde
or keto group) e.g. maltose, lactose
Non-reducing disacharides (having no free
aldehyde or keto group) e.g. sucrose

30. An -OH (alcohol) of
one glucose (right)
condenses with
intramolecular
hemiacetal
of the other glucose
(left), with
elimination of H
2O
and formation of an
O-glycosidic bond.
The reversal of
this reaction is
hydrolysis—attack by
H
2
O on the glycosidic
bond.
The maltose
molecule retains a
reducing hemiacetal
at the C-1 not
involved in the
glycosidic bond.

31. Malt-sugar

32. Milk-sugar

33. Table-sugar

34. MALTOSE, SUCROSE, & LACTOSE ARE
IMPORTANT DISACCHARIDES
Lactase and sucrase deficiencies- malabsorption leads to
diarrhea and flatulence.

35. Sugars Form Glycosides With Other
Compounds & With Each Other
Glycosides –
• formed by condensation between the hydroxyl group of the
anomeric carbon of a monosaccharide, or monosaccharide
residue, and a second compound that may—or may not (in the
case of an aglycone)—be another monosaccharide.
• If the second group is a hydroxyl, the O-glycosidic bond is
an acetal link because it results from a reaction between a
hemiacetal group (formed from an aldehyde and an -OH
group) and an-other -OH group.
• If the hemiacetal portion is glucose, the resulting compound
is a glucoside; if galactose, a galactoside.

36. Sugars Form Glycosides With Other Compounds
& each Other
• If the second group is an amine, an N-glycosidic bond is
formed, e.g. between adenine and ribose in nucleotides such as
ATP .
• Glycosides are widely distributed in nature; the aglycone may
be methanol, glycerol, a sterol, a phenol, or a base such as
adenine.
• The glycosides that are important in medicine because of their
action on the heart (cardiac glycosides) all contain steroids as
the aglycone.
• These include derivatives of digitalis and strophanthus such as
ouabain, an inhibitor of the Na
+
-K
+
ATPase of cell membranes
and antibiotics such as streptomycin.

37. Deoxy Sugars Lack an Oxygen Atom
a hydroxyl group has been replaced by hydrogen--
deoxyribose in DNA.

38. Oligosaccharides
Trisaccharide: raffinose (glucose, galactose
and fructose)
Tetrasaccharide: stachyose (2 galactoses,
glucose and fructose)
Pentasaccharide: verbascose (3 galactoses,
glucose and fructose)
Hexasaccharide: ajugose (4 galactoses,
glucose and fructose)

39. starch
Structures of some
oligosaccharides

40. Structures of some oligosaccharides

41. Structures of some oligosaccharides

42. Oligosaccharides occur widely as components of
antibiotics derived from various sources

43. POLYSACHARIDES

44. Definition & Classification
Polysacharides are linear as well as
branched chain polymers of monosacharides
or their derivatives, held together by
glycosidic bonds
Polysacharides are of two types
Homopolysacharides: which on hydrolysis yield
only a single type of monosacharide
Heteropolysacharides: which on hydrolysis yield
a mixture of a few monosacharides or their
derivatives

45. Polysaccharides or glycans
homoglycans (starch, cellulose, glycogen, inulin)
heteroglycans (gums, mucopolysaccharides)
functions: serve storage and structural function
characteristics:

polymers (MW from 200,000)

White and amorphous products (glassy)

not sweet

not reducing; do not give the typical aldose or ketose
reactions)

form colloidal solutions or suspensions

46. HOMOPOLYSACHARIDES
When the polysacharides are composed of
same types of monosacharides or their
derivatives, they are referred to as
homopolysacharides or homoglycans

47. Starch
most common storage polysaccharide in
plants
composed of 10 – 30% amylose and 70-
90% amylopectin depending on the source
the chains are of varying length, having
molecular weights from several thousands to
half a million

48. Amylose
Amylose has a non-branching helical structure composed of
glucose residues

49. Amylopectin
amylopectin consists of branched chains composed of 24–30
glucose residues united by 1 4 linkages in the chains and by 1
→
6 linkages at the branch points.
→

50. Amylose and amylopectin are the 2 forms of starch. Amylopectin
is a highly branched structure, with branches occurring every 12
to 30 residues

51. suspensions of amylose
in water adopt a helical
conformation
iodine (I
2
) can insert in
the middle of the
amylose
helix to give a blue color
that is characteristic and
diagnostic for starch

52. Glycogen
also known as animal starch
stored in muscle and liver
present in cells as granules (high
MW)
contains both (1,4) links and
(1,6) branches at every 8 to 12
glucose unit
complete hydrolysis yields glucose
glycogen and iodine gives a red-
violet color
hydrolyzed by both  and -
amylases and by glycogen
phosphorylase

53. Glycogen is highly branched structure with chains of
12–14 α-D-glucopyranose residues (in α[1 4]-
→
glucosidic linkage), with branching by α(1 6)-
→
glucosidic bonds.
A: General structure. B: Enlargement of structure at a branch point.

54. Inulin
-(1,2) linked fructofuranoses
linear only; no branching
lower molecular weight than starch
colors yellow with iodine
hydrolysis yields fructose
sources include onions, garlic, dandelions and
jerusalem artichokes
used as diagnostic agent for the evaluation of
glomerular filtration rate (renal function test)
Jerusalem artichokes

55. Chitin
Chitin is the second most
abundant carbohydrate
polymer
consists of N-acetyl-D-
glucosamine units joined
by β (1 →4)-glycosidic
linkages
Present in the cell wall of
fungi and in the
exoskeletons of
crustaceans, insects and
spiders
Chitin is used
commercially in coatings
(extends the shelf life of
fruits and meats)

56. Dextrins
produced by the partial hydrolysis of starch
along with maltose and glucose
dextrins are often referred to as either
amylodextrins, erythrodextrins or
achrodextrins
used as mucilages (glues)
also used in infant formulas (prevent the
curdling of milk in baby’s stomach)

57. Dextrans
- are bacterial and yeast polysaccharides made up of (α1-6)-
linked poly-D-glucose having (α 1-3) branches
•- Dental plaque, formed by bacteria growth is rich in dextrans.
•--Plasma expanders- high viscosity, low osmotic pressure, slow
disintigration and utilization-

58. Cellulose
Chief constituent of the
framework of plants
Polymer of -D-glucose
attached by (1,4) linkages
Yields glucose upon complete
hydrolysis
Most abundant of all
carbohydrates

Cotton flax: 97-99%
cellulose

Wood: ~ 50% cellulose
Gives no color with iodine
cannot be digested by
mammals
an important source of “bulk”
in the diet

59. Linear structures of cellulose and chitin
(2 most abundant polysaccharides)

60. Learning Check
Identify the polysaccharide in each as:
A. B. C.

61. HETEROPOLYSACHARIDES
When the polysacharides are composed of different
types of sugars or their derivatives, they are referred
to as heteropolysacharides or heteroglycans
Mucopolysacharides: made up of repeating units of
sugar derivatives which are aminosugars
(glycosaaminoglycans or GAG)
Mucoproteins: mucopolysacharide in combination
with proteins (proteoglycans)
Important mucopolysacharides: hyaluronic acid,
chondroitin sulphate, hepatin, dermatan sulphate &
keratan sulphate

62. Amino Sugars (Hexosamines) are Components
of Glycoproteins, Gangliosides, &
Glycosaminoglycans
The amino sugars include D-glucosamine, a constituent of
hyaluronic acid, D-galactosamine (chondrosamine), a
constituent of chondroitin.
Several antibiotics (eg, erythromycin) contain amino
sugars believed to be important for their antibiotic activity.

63. Hyaluronic acid
Important GAG found in the ground
substance of synovial fluid of joints and
vitreous humor of eyes
Serve as lubricant and shock absorbent in
joints
Composed of alternate units of D-glucuronic
acid and N-acetyl-D-glucosamine
Hyaluronidase is an enzyme that breaks the
bonds in hyaluronic acid

64. Hyaluronate:
material used
to cement the
cells into a
tissue

65. Hyaluronic acid derivatives
several products are used in the
management of osteoarthritis symptoms
Hyalagan and Synvisc
others are used as ophthalmic surgical
adjuncts in cataract extractions, intraocular
lens implantation, corneal transplant and
retinal attachment surgery (Healon, Amvisc,
AMO Vitrax)

66. Chondroitin sulphate
Major constituent of various mammalian
tissues (bone, cartilage, tendons, heart,
valves, skin etc.)
Composed of repeating units of D-glucuronic
acid and N-acetyl D-galactosamine 4-sulfate

67. Heparin
It is an anticoagulant that occurs in blood,
lungs, liver, kidney etc
Composed of alternating units of N-sulfo D-
glucosamine 6-sulfate and glucuronate 2-
sulfate

68. Dermatan sulfate
Excessively found in skin
It maintains the shape of the tissues
Composed of L-Iduronic acid and N-acetyl D-
galactosamine 4-sulfates

69. Keratan sulfate
Found in cartilage, cornea, connective tissues
etc.
It helps to keep cornea transparent
Formed by repeating units of D-
galactosamine and N-acetylglucosamine 6-
sulfate

70. Glycosaminoglycans

71. Glycosaminoglycans

72. Glycosaminoglycans

73. Pectin
pectins are heteropolysaccharides found in
the pulp of fruits (citrus, apples)
on hydrolysis pectins yield galacturonic acid,
galactose, arabinose, methanol and acetic
acid
pectins are composed of galactans and
arabans
used as gelling agents (to make jellies)

74. Gums
widely used in the food and pharmaceutical industry
used as: suspending agents, gelling agents,
thickening agents, emulsifiers, foam stabilizers,
crystallization inhibitors, adhesives, binding agents
agar, tragacanth, karaya, carrageenan, guar gum,
gum arabic (acacia), furcellaran, sodium alginate,
locust bean gum

75. Bacterial cell wall
provide strength and rigidity for the bacteria
consists of a polypeptide-polysaccharide
known as petidoglycan
determines the Gram staining characteristic
of the bacteria

76. Structure of
peptidoglycan

77. Cell wall of Gram-positive
bacteria

78. Cell wall of Gram-negative bacteria

79. Lipopolysaccharide (LPS)
coats the outer membrane
of Gram-negative bacteria.
The lipid portion of the
LPS is embedded in the
outer membrane and is
linked to a complex
polysaccharide

80. Glycoproteins
Proteins covalently bound to carbohydrates
are known as glycoproteins
Usually done as a post-translational process
Proteins can contain either O-linked
oligosaccharides or N-linked oligosaccharides
Collagen, ceruloplasmin, immunoglobulins,
thyrotropin, fibrinogen etc are importnant
examples of glycoproteins

81. These glycoproteins are found in
The blood of Arctic and Antarctic
fish enabling these to live at sub-
zero water temperatures

82. Proteoglycans are a family of
glycoproteins whose carbohydrate
moieties are predominantly
glycosaminoglycans
structures are quite diverse
examples: versican, serglycin,
decorin, syndecan
Functions:
- modulate cell growth processes
- provide flexibility and
resiliency to cartilage