Understanding carbohydrates

1. CARBOHYDRATES
Presented by;
M Pharm (Pharmaceutical Chemistry) students
Gunturu .Aparna
Akshintala. Sree Gayatri
Thota. Madhu latha
Kamre. Sunil
Daram. Sekhar
University college of pharmaceutical sciences
Department of pharmaceutical chemistry
Acharya Nagarjuna University
Guntur
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 Cells of organisms - plants, fungi, bacteria.
 Insects, animals - produce a large variety of
organic compounds.
 Many substances were obtained anciently, e.g.
foodstuffs, building materials, dyes, medicinals, and
other extracts from nature.

4.  Oils & Fats, Terpenoids
 Prostaglandins Alkaloids,
 Vitamins Flavanoids
 Steroids Carbohydrates
 Lignins lignans
 Proteins Nucleic acid
 Antibiotics pigments
EXAMPLES OF NATURAL PRODUCTS
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6. CARBOHYDRATES
 Carbohydrates are the most abundant organic compounds in
the plant world.
 They act as storehouses of chemical energy (glucose, starch,
glycogen); are the components of supportive structures in plants
(cellulose), crustacean shells (chitin) and connective tissues in
animals (acidic polysaccharides) and are essential components of
nucleic acids (D-ribose and 2-deoxy-D-ribose).
 Carbohydrates make up about three fourths of the dry weight of
plants.
.
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8.  Simple Sugars
Monosaccharides
Disaccharides
 Complex Carbohydrates
Starch
Glycogen
Cellulose (a form of fiber)
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9. A. Structure and Nomenclature
 The general formula CnH2nOn
 with one of the carbons being the carbonyl group of either an
aldehyde or a ketone.
 The most common monosaccharides have three to eight carbon
atoms.
 The suffix-ose indicates that a molecule is a carbohydrate, and
the prefixes tri-, tetr-, pent-, and so forth indicate the number of
carbon atoms in the chain.
 Monosaccharide containing an aldehyde group are classified
as aldoses; those containing a ketone group are classified as
ketoses.
 A ketose can also be indicated with the suffix ulose; thus, a
five- carbon ketose is also termed a Pentulose.
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10.  Another type of classification scheme is based on the
hydrolysis of certain carbohydrates to simpler
carbohydrates i.e. classifications based on number of
sugar units in total chain.
 Monosaccharides: single sugar unit
 Disaccharides: two sugar units
 Oligosaccharides: 3 to 10 sugar units
 Polysaccharides: more than 10 units
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11. Sucrose (C12H22O11) + H2O acid or certain enzyme Glucose (C6H12O6) + Fructose (C6H12O6)
Monosaccharides
Disaccharides
There are only two trioses: the aldotriose glyceraldehyde and the
ketotriose dihydroxyacetone
Glyceraldehyde
(an aldotriose)
CHO
CHOH
CH2OH
CH2OH
C
CH2OH
O
Didroxyacetone
(a ketotriose)
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12.  We will consider the stereochemistry of
carbohydrates by focusing largely on the aldoses
with six or fewer carbons.
 The aldo hexoses have four asymmetric carbons and
therefore exist as 24 or 16 possible stereo isomers.
 These can be divided into two enantiomeric sets of
eight diastereomers.
HOH2C
OH
H
C
OH
H
C
OH
H
C
H
C
OH
C
H
O
Aldohexoses
four asymmetric carbons
24
= 16 stereoisomers
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13.  Similarly, there are two enantiomeric sets of four
diastereomers (eight stereoisomers total) in the aldopentose
series. Each diastereomer is a different carbohydrate with
different properties, known by a different name.
 The aldoses with six or fewer carbons are given as Fischer
projections. Be sure you understand how to draw and interpret
Fischer projections, as they are widely used in carbohydrate
chemistry.
 Each of the monosaccharides has an enantiomer. For
example, the two enantiomers of glucose have the following
structures: HC
OH
H
H
HO
OH
H
OH
H
CH2OH
HC
HO H
H OH
HO H
HO H
CH2OH
O
Enantiomers of glucose
D - L -
O
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14.  It is important to specify the enantiomers of
carbohydrates in a simple way.
 Suppose you had a model of one of these glucose
enantiomers in your hand. You could, of course, use
the R,S system to describe the configuration of one
or more of the asymmetric carbon atoms.
 A different system, however, was in use long before
the R,S system was established.
 The D,L system, which came from proposals made
in 1906 by M. A. Rosanoff, is used for this purpose.
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15.  Glyceraldehydes contains a chiral center and therefore exists
as a pair of enantiomers.
 Glyceraldehyde is a common name; the IUPAC name for this
monosaccharide is 2,3-dihydroxypropanal.
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16.  Chemists commonly use two-dimensional
representations called Fischer projections to show the
configuration of carbohydrates.
 Following is an illustration of how a three-dimensional
representation is converted to a Fischer projection.
CHO
C
H OH
CH2OH
CHO
C H
HO
CH2OH
(R)-Glyceraldehyde (S)-Glyceraldehyde
4 C
3
1
2
4 C
2
1
3
(S) (R)
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17. CHO
HO H
H OH
H OH
CH2OH
CHO
H OH
HO H
H OH
CH2OH
CHO
HO H
HO H
H OH
CH2OH
CHO
H OH
H OH
H OH
CH2OH
D-(-)-ribose
(2R,3R,4R)
D-(-)-arabinose
(2S,3R,4R)
D-
(+)-xylose
(2R,3S,4R)
D-(-)-lyxose
(2S,3S,4R)
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18. CHO
H OH
H OH
CH2OH
CHO
HO H
H OH
CH2OH
D-(-)-Erythrose D-(-)-Threose
CHO
H OH
H OH
H OH
CH2OH
D-(-)-Ribose
H
OH
O
OH
H2
C
HO
H
O
OH
H2
C
HO
OH
H
OH
O
OH
C
H2
OH
HO
4
3
2
1
5
2(R),3(R),4(R),5-tetrahydroxypentanal
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19.  Even though the R,S system is widely accepted today as a
standard for designating configuration, the configuration of
carbohydrates as well as those of amino acids and many other
compounds in biochemistry is commonly designated by the D,L
system proposed by Emil Fischer in 1891.
 At that time, it was known that one enantiomer of glyceraldehyde
has a specific rotation of + 13.5; the other has a specific rotation of
-13.5.
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20.  Fischer proposed that these enantiomers be
designated D and L (for dextro and levorotatory) but
he had no experimental way to determine which
enantiomer has which specific rotation.
 Fischer, therefore, did the only possible thing-he
made an arbitrary assignment.
 He assigned the dextrorotatory enantiomer an
arbitrary configuration and named it D-
glyceraldehyde. He named its enantiomer L-
glyceraldehyde.
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21.  Fischer could have been wrong, but by a stroke of good
fortune he was correct, as proven in 1952 by a special
application of X-ray crystallography.
 D- and L-glyceraldehyde serve as reference points for the
assignment of relative configuration to all other aldoses and
ketoses.
CHO
C
H OH
CH2OH
D-Glyceraldehyde
[]D = +13.5
CHO
C H
HO
CH2OH
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L-Glyceraldehyde
[]D = -13.5
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22.  The reference point is the chiral center farthest from
the carbonyl group. Because this chiral center is
always the next to the last carbon on the chain, it is
called the penultimate carbon.
 A D-monosaccharide has the same configuration at
its penultimate carbon as D-glyceraldehyde (its-OH
is on the right when written as a Fischer projection);
an L-monosaccharide has the same configuration at
its penultimate carbon as L-glyceraldehyde.
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23. CHO
C
H OH
CH2OH
*
D-Glyceraldehyde
CHO
H OH
H OH*
CH2OH
CHO
HO H
H OH*
CH2OH
D-Erythrose D-Threose
CHO
H OH
H OH
H OH*
CH2OH
CHO
HO H
H OH
H OH*
CH2OH
CHO
H OH
HO H
H OH*
CH2OH
CHO
HO H
HO H
H OH*
CH2OH
D-Ribose D-Arabinose D-Xylose D-Lyxose
CHO
OH
H
OH
H
OH
H
OH*
H
CH2OH
CHO
H
HO
OH
H
OH
H
OH*
H
CH2OH
CHO
OH
H
H
HO
OH
H
OH*
H
CH2OH
CHO
H
HO
H
HO
OH
H
OH*
H
CH2OH
CHO
OH
H
OH
H
H
HO
OH*
H
CH2OH
CHO
H
HO
OH
H
H
HO
OH*
H
CH2OH
CHO
OH
H
H
HO
H
HO
OH*
H
CH2OH CHO
H OH
*
H OH
H OH
HO H
CH2O
H
D-Allose D-Altrose D-Glucose D-Mannose D-Gulose D-Talose
D-Galactose
D-Idose
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24.  Three main disaccharides: sucrose
maltose
lactose
 All are isomers with molecular formula
C12H22O11
 On hydrolysis they yield 2 monosaccharide.
 which soluble in water
 Even though they are soluble in water, they
are too large to pass through the cell
membrane.
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25.  Is a sugar used at home
 Also known as the cane sugar
 When hydrolyzed, it forms a mixture of
glucose and fructose
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27.  Commonly known as malt sugar.
 Present in germinating grain.
 Produced commercially by hydrolysis of
starch.
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29.  Commercially known as milk sugar.
 Bacteria cause fermentation of lactose
forming lactic acid.
 When these reaction occur ,it changes the
taste to a sour one.
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32.  Sucrose and maltose will ferment when yeast
is added because yeast contains the enzyme
sucrase and maltase.
 Lactose will not ferment because yeast does
not contain lactase.
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33.  The chemical reactions of these sugars can
be used to distinguish them in the
laboratory.
 If you have 2 test tubes containing a
disaccharide, C12H22O11.
 To determine if it is sucrose lactose or
maltose.
 We can use the alkaline Cu complex
reaction of glucose and the principle of
fermentation.
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34.  Polysaccharides are large molecules
containing 10 or more monosaccharide units.
Carbohydrate units are connected in one
continuous chain or the chain can be
branched.
1. Storage polysaccharides contain only -
glucose units. Three important ones are
starch, glycogen, and amylopectin.
2. Structural polysaccharides contain only -
glucose units. Two important ones are
cellulose and chitin. Chitin contains a
modified -glucose unit
Polysaccharides
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36. Amylose and amylopectin—starch
 Starch is a mixture of amylose and amylopectin and is
found in plant foods.
 Amylose makes up 20% of plant starch and is made
up of 250–4000 D-glucose units bonded α(1→4) in a
continuous chain.
 Long chains of amylose tend to coil.
 Amylopectin makes up 80% of plant starch and is
made up of D-glucose units connected by α(1→4)
glycosidic bonds.
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37.  Glycogen is a storage polysaccharide found in
animals.
 Glycogen is stored in the liver and muscles.
 Its structure is identical to amylopectin, except that
α(1→6) branching occurs about every
12 glucose units.
 When glucose is needed, glycogen is hydrolyzed in
the liver to glucose.
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38. Structural Polysaccharides
Cellulose
 Cellulose contains glucose units bonded (1→4).
 This glycosidic bond configuration changes the
three-dimensional shape of cellulose compared with
that of amylose.
 The chain of glucose units is straight. This allows
chains to align next to each other to form a strong
rigid structure.
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40.  Cellulose is an insoluble fiber in our diet
because we lack the enzyme cellulase to
hydrolyze the (1→4) glycosidic bond.
 Whole grains are a good source of cellulose.
 Cellulose is important in our diet because it
assists with digestive movement in the small
and large intestine.
 Some animals and insects can digest cellulose
because they contain bacteria that produce
cellulase.
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41. Chitin
 Chitin makes up the exoskeleton of insects
and crustaceans and cell walls of some fungi.
 It is made up of N-acetyl glucosamine
containing (1→4) glycosidic bonds.
 It is structurally strong.
 Chitin is used as surgical thread that
biodegrades as a wound heals.
 It serves as a protection from water in insects.
 Chitin is also used to waterproof paper, and in
cosmetics and lotions to retain moisture.
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43. Heparin:
 Heparin is a medically important
polysaccharide because it prevents clotting in the
bloodstream.
 It is a highly ionic polysaccharide of repeating
disaccharide units of an oxidized monosaccharide
and D-glucosamine. Heparin also contains sulfate
groups that are negatively charged.
 It belongs to a group of polysaccharides called
glycosaminoglycans.
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