REVISED CHEMISTRY OF CARBOHYDRATES.ppt 1.2

CARBOHYDRATE
CHEMISTRY
Biochemist Fred
0706219211
0787692463
bwambale01fred@gmail.com

DEFINITION
 Carbohydrates are polyhydroxy aldehydes or
ketones or compounds which yield these on
hydrolysis.
C
C O
H
H
C H
H
O
C O
H
H
C O
H
H
C
H
2
O
H
D
-glu
co
se
O
H
C H
HO
C OH
H
C OH
H
CH2OH
CH2OH
C O
D-fructose

BIOMEDICAL IMPORTANCE
1. Most abundant dietary source of energy.
2. Also serve as storage form of energy –
Glycogen.
3. Participate in the structure of cell membrane
& cellular functions (cell growth, adhesion and
fertilization).
4. Mucopolysaccharides form the ground
substance of mesenchymal tissues.
5. Certain carbohydrate derivatives are used as
drugs, like cardiac glycosides / antibiotics.

ASSOCIATED DISORDERS
 Derangement in Glucose metabolism –
Diabetes Mellitus.
 Inherited deficiency of certain enzymes in
metabolic pathways of different carbohydrates
cause diseases.
• Glycogen storage disorders
• Galactosemia
• Hereditary fructose intolerence
• Lactose intolerance, etc.

CLASSIFICATION
 Based on number of sugar units present.
 Monosaccharides.
 Cannot be hydrolyzed further into simpler forms.
 Disaccharides.
 Yield 2 molecules of same or different
monosaccharide units on hydrolysis.
 Oligosaccharides.
 Yield 3-10 molecules of monosaccharide units on
hydrolysis.
 Polysaccharides.
 Yield more than 10 molecules of same or different
monosaccharide units on hydrolysis.
 Homo- & Heteropolysaccharides.

MONOSACCHARIDES
 Simplest group of carbohydrates, cannot be further
hydrolysed.
 General formula : Cn(H2O)n
 Categorization of monosaccharides is based on
 the Functional Group. (Aldehyde or keto)
 the Number of Carbon atoms.

MONOSACCHARIDES BASED ON
FUNCTIONAL GROUP
ALDOSE
KETOSE

COMMON MONOSACCHARIDES
No. of C
atoms
Generic name Aldoses Ketoses
3 Triose Glyceraldehyde Dihydroxy acetone
4 Tetrose Erythrose Erythrulose
5 Pentose Ribose
Xylose
Rilulose
Xylulose
6 Hexose Glucose
Galactose
Fructose
7 Heptose Glucoheptose Sedoheptulose

STEREOISOMERS
 Compounds having same structural formula, but differ
in spatial configuration.
 Asymmetric Carbon atom: Attached to four different
atoms or groups.
 Vant Hoff’s rule: The possible isomers (2n
) of a given
compound is determined by the number of asymmetric
carbon atoms (n).
 Reference C atom: Penultimate C atom, around which
mirror images are formed.

OPTICAL ACTIVITY
Dextrorotatory (+) : If the sugar solution
turns the plane of polarized light to right.
Levorotatory (–) : If the sugar solution
turns the plane of polarized light to left.
Racemic mixture: Equimolar mixture of
optical isomers has no net rotation.

REACTIONS OF
MONOSACCHARIDES
 Reducing properties.
 Oxidation.
 Reduction.
 Dehydration.
 Formation of Esters
 Glycoside formation.

REDUCING PROPERTIES
 Attributed to the free aldehyde or keto group of
anomeric carbon.
 Tests done to identify the reducing action of sugars
include :
 Benedict’s test.
 Barfoed’s test.
 Fehling’s test.
 Osazone test.
 Reduction is more efficient in alkaline medium than in
acidic medium.

SUGAR ENEDIOL
SUGAR ACID
Cu++
CuSO4
Cu+
2Cu(OH)2
Cu2O
OXIDISED REDUCED
BENEDICT’S TEST: PRINCIPLE
REAGENT: Na2CO3, CuSO4, Na citrate

BENEDICT’S TEST
water Benedict’s 0.5-1% 1- 1.5% 1.5– 2%

BARFOED’S TEST
 Reducing monosaccharides are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of cuprous oxide within three minutes.
Red scum at
bottom

FEHLING’S TEST
 Fehling I:CuSO4
 Fehling II: K-Na- tartrate + NaOH
 Fehling's reagent: Equal volumes of Fehling I and
Fehling II are mixed to form a deep blue solution.

OSAZONE FORMATION
 Phenylhydrazine in acetic acid, when boiled with
reducing sugars, forms osazones.
FRUCTOSE
PHENYL
HYDRAZINE FRUCTOSAZONE

GLUCOSAZONE:NEEDLE SHAPED
LACTOSAZONE: HEDGEHOG
SHAPED MALTOSAZONE: SUNFLOWER
SHAPED
OSAZONE CRYSTALS

OXIDATION
C
C O
H
H
C H
H
O
C O
H
H
C O
H
H
C
H2O
H
D-glucose
O
H
Gluconic acid
Glucuronic acid
Glucosaccharic
acid

 Furfurals condense with phenolic compounds (-naphthol)
to form coloured products.
 Basis of the “Molisch test”.
1
2
3
4
5
6
Conc. H2SO4
3H2O
DEHYDRATION

FORMATION OF ESTERS
 Esterification of alcoholic groups of mono-saccharides
with phosphoric acid is a common reaction in
metabolism.
 Examples :
 Glucose-6-phosphate, and
 Glucose-1-phosphate.
 ATP donates the phosphate moiety.

GLYCOSIDE FORMATION
 The hydroxyl group of anomeric carbon of a carbohydrate
can join with a hydroxyl group of another carbohydrate
or some other compound to form a glycoside and the bond
so formed is known as glycosidic bond.
eg. R-OH + HO-R'  R-O-R' + H2O
 Carbohydrate moiety-Glycone
 The non-carbohydrate moiety is known as aglycone –
phenol, sterol, bases, CH3OH, glycerol.
 Glycosidic bond can be N-linked or, O-linked.

N-Glycosidic linkage O- Glycosidic linkage
N & O GLYCOSIDIC LINKAGE

BIOMEDICAL IMPORTANCE OF
GLYCOSIDES
 Cardiac Glycosides – Digoxin, Digitoxin
 Used in cardiac insufficiency.
 Contain steroids as aglycone component.
 Ouabain – Na+
/K+
pump inhibitor, (Binding to ATPase)
 Streptomycin – Antibiotic (aminoglycosides)
 Phloridzin – cause renal damage, glycosuria.
 Obtained from root & bark of apple tree.
 Blocks the transport of sugar across the mucosal cells
of small intestine & also renal tubular epithelium.

DEOXY SUGARS
 Oxygen of the hydroxyl group is removed to form deoxy
sugars.
 Non reducing and non osazone forming.
 Important part of nucleic acids.

DISACCHARIDES
 Two monosaccharides combined together by glycosidic
linkage.
 Reducing : Maltose, Lactose – with free
aldehyde or keto group.
 Non-reducing: Sucrose, Trehalose – no free
aldehyde or keto group.

SUCROSE
 Cane sugar.
 α-D-glucose & β-D-fructose
units held together by (α1 β2)
glycosidic bond.
 Reducing groups in both are
involved in bond formation,
hence non reducing.

INVERT SUGAR
 Sucrose is dextrorotatory. (+66.50
)
 During hydrolysis, sucrose is first split into α-D-
glucopyranose & β-D-fructofuranose (both
dextrorotatory).
 β-D-fructofuranose is less stable and immediately
converted to β-D-fructopyranose (strongly levorotatory).
 Net rotation : – 28.20
.
 Sweeter than sucrose.

TREHALOSE
 1- 1 glycosidic linkage
C
C
CH2OH
H OH
C
OH
H C
H
HO
H OH
C O
H
D-Glucose
C
C
CH2OH
H OH
C
OH
H C
H
HO
H OH
C O
H
D-Glucose

LACTOSE
 Present in milk.
 β-D-galactose & β-D-
glucose units held
together by β (14)
glycosidic bond.

MALTOSE
Malt sugar.
Produced during the course of
digestion of starch by the enzyme
amylase.
Two α-D-glucose units held together
by α (14) glycosidic bond.

POLYSACCHARIDE
 Repeat units of monosaccharides or their derivatives
held together by glycosidic bonds.

HOMOPOLYSACCHARIDES
 Starch
 Glycogen
 Cellulose
 Inulin
 Dextrans
 Chitin

STARCH
 Carbohydrate reserve of
plants. Present in
Cereals, Roots, Tuber,
Vegetables.
 Consists of Amylose
(water soluble) &
Amylopectin (water
insoluble).

AMYLOSE
 Long unbranched chain.
 200 – 20,000 D-glucose units held together by α (14)
glycosidic linkages.
AMYLOSE

AMYLOPECTIN
 Branched chain. (α 16 glycosidic bonds at branches).
 20 – 30 glucose units per branch.
AMYLOPECTIN

HYDROLYSIS OF STARCH
 Colour disappears with heating and reappears when
cooled.
 Starch is non reducing.
 Hydrolysis for a short time: Violet colour due to
Amylopectin (non reducing).
 Further hydrolysis: Red colour due to Erythrodextrin
(reducing).
 Later Achrodextrin & Maltose (both reducing).
+ve -ve

ACTION OF AMYLASE
 Starch Dextrins α/ß-Maltose
 Amylopectin
Maltoses
Salivary &
pancreatic α-
amylase or ß-
amylase
ß-amylase
Limit dextrin

GLYCOGEN
 Reserve carbohydrate in
animals. Stored in liver &
muscle.
 Forms red-brown/brown-
violet colour with iodine.
 Contains primer protein:
Glycogenin.
 More branched and
compact than amylopectin.
Every 11th sugar molecule
has a branch.

CELLULOSE
 Chief carbohydrate in plants.
 Made up of glucose units combined with cellobiose
bridges.
 No branching point.
 Cannot be digested by human due to absence of
Cellobiase.

INULIN
 Inulin is made up of D-
fructose units with
repeating ß-1,2 linkages.
 It acts as a marker for
glomerular filtration since
it is not synthesized,
metabolized but filtered
completely by glomerulus.

CHITIN
Chitin is found in crustaceans
eg.lobsters,crabs,shrimps,insects.
Composed of N-acetyl
glucosamine units joined by ß-1,4
glycosidic linkages.

HETEROPOLYSACCHARIDES
 Agar
 Mucopolysaccharides:
 Hyaluronic acid
 Heparin
 Chondroitin sulphate
 Keratan sulphate
 Dermatan sulphate

AGAR
 Prepared from sea weeds.
 Contains Galactose, Glucose
and other sugars.
 Used as supporting medium
for immunodiffusion &
immunoelectrophoresis.
 Agarose contains Galactose
combined with3,6
anhydrogalactose units.
 Agarose is used as matrix for
electrophoresis.

MUCOPOLYSACCHARIDES
 Also known as GAG.
 Made up of repeating units of sugar derivatives
(aminosugars and uronic acids).
 Acetylated amino groups, sulfates and carboxyl groups
are generally present.

HYALURONIC ACID
 Present in connective tissues, tendons, synovial fluid and
vitreous humor.
 Composed of repeating units of N-acetyl glucosamine →
ß-1,4 glucuronic acid → ß-1,3 N-acetyl glucosamine.

HEPARIN
 Anticoagulant. Bind and activate Antithrombin III,
which in turn activates Thrombin, Factor X & Factor
IX.
 Present in lung, spleen and monocytes.
 Contains repeating units of sulphated glucosamine → α-
1,4 L-iduronic acid.
 Sulphated: Heparan sulphate

CHONDROITIN SULPHATE
 Present in ground substances of connective tissues of
cartilages, bones & tendons.
 Composed of Glucuronic acid → ß-1,3 N-acetyl
galactosamine sulphate → ß-1,4 and so on.

KERATAN SULPHATE
 Only GAG not having Uronic acid.
 Found in cornea and tendons.
 Repeating units are Galactose & N-acetyl galactosamine
in ß linkage.

DERMATAN SULPHATE
 Found in skin, blood vessels & heart vessels.
 Contains L-iduronic acidand N-acetyl galactosamine in
ß-1,3 linkage.

REVISED CHEMISTRY OF CARBOHYDRATES.ppt 1.2

REVISED CHEMISTRY OF CARBOHYDRATES.ppt 1.2

More Related Content

Similar to REVISED CHEMISTRY OF CARBOHYDRATES.ppt 1.2

Recently uploaded

REVISED CHEMISTRY OF CARBOHYDRATES.ppt 1.2