Download - The Vignanam

School of Biotechnology
Vignan University, Vadlamudi
Carbohydrates
Monosaccharide
Disaccharides
 SWEET
 SWEET
 FRUIT (GRAPES)
 FRUIT
(SUGARCANE)
Polysaccharides
 DO NOT TASTE
SWEET
 PLANT
FUNCTIONS
• Structural – cellulose, chitin, peptidoglycan
• Energy storage – starch, glycogen
• Biologically active:
– Transport – glycoproteins in plasma (transferring)
– Regulatory – glycoproteins like FSH, LH, TSH
– Catalytic – glycoproteins (ribonuclease, -amylase)
– Immune response – Ig, interferons, Rh factors
– Cell lubrication & supportive function – sialoglycoproteins
– Cell differentiation – ABO blood grouping
– Cell membrane, clotting factors, & protective cellular coat
proteins – glycocalyx, fibrinogen, prothrombin
INTRODUCTION
 Carbohydrates are an important source of energy that
can be use by cells.
 From the word Carbohydrates,
 “carbo” refer to element Carbon
 “hydrates” refer to water (H2O)
 Containing of Carbon, Hydrogen, and Oxygen.
 The ratio of hydrogen atoms to oxygen atoms in one
molecule of carbohydrates is 2 : 1.
 The empirical formula = Cm(H2O)n
General characteristics
• Carbohydrates are
molecules in nature.
the
most
abundant
organic
• In plants, glucose is synthesized from carbon dioxide
and water by photosynthesis and stored as starch or
is converted to cellulose of the plant framework.
• Carbohydrates perform both structural and metabolic
roles.
• Carbohydrates are Poly-hydroxy-aldehydes,
hydroxy-ketones, or their polymers
• Carbohydrates are also named saccharides Latin,
or
poly-
Important biological Functions
of Carbohydrates
1.
Source of energy (Metabolic fuel: glucose)
2.
Storage of energy as starch (in plants) and glycogen
(in animals)
3.
Form structural tissues in plants (cellulose), in
bacteria (cell-wall), and animals: proteoglycans in
cartilage, teeth ..
4.
Found in plasma membrane and play a role in cell
recognition
5.
Glucose can be converted into fats and proteins
6.
Ribose sugar is important in the formation of nucleic
acids (RNA and DNA)
Classification of Carbohydrates
• 1- Monosaccharides: formed of one sugar unit
Ex: Glucose, Ribose, Galactose, Fructose, Mannose
• 2- Disaccharides: formed of two sugar units
Ex: Maltose , Sucrose , Lactose
• 3- Oligosaccharides: formed of 3 – 12 sugar
units
• 4- Polysaccharides (glycans): formed of more
than 12 sugar units
• Homopolysaccharides: Starch, Glycogen, Cellulose
• Heteropolysaccharides: Chondroitin sulfate, Heparin
Types of Carbohydrate
• Monosaccharides
• Disaccharides
• Polysaccharides
MONOSACCHARIDES
 It is monomer of carbohydrates.
 known as simple sugar.
 main source of energy for many cells.
 glucose can be found in plants and fruits
 fructose can be found in sweet fruit and honey
 galactose can be found in milk
 C6H12O6
Characteristic of monosaccharides





Taste sweet.
Able to crystallize
Water soluble
Simplest carbohydrates.
Reducing sugar
 when heated with Benedict’s solution,
monosaccharides reduce the blue copper (II)
sulphate solution to a brick-red precipitate,
copper (I) oxide. Monosaccharides are
reducing sugars.
carbon
Elements
oxygen
Glucose
hydrogen
Fructose
Galactose
Monosaccharide
Maltose
Types
Sucrose
Disaccharide
Lactose
Starch
Polysaccharide
Cellulose
Glycogen
Condensation
+
+ H2O
Reaction
Hydrolysis
+ H2O
+
Monosaccharides
General formula: (CH2O)n
Smallest has 3 carbons e.g. glyceraldehyde
CLASSIFICATION OF MONSACCHARIDES:
Can be carried out by one of two methods:
1. According to the number of carbon atoms:
• 1- Trioses : Contain 3 carbon atoms. e.g.
Glyceraldehyde - Dihydroxy Acetone (DHA)
• 2- Tetroses : Contain 4 carbon atoms. e.g.
Erythrose
• 3- Pentoses: Contain 5 carbon atoms. e.g. Ribose
- Xylulose
• 4- Hexoses : Contain 6 carbon atoms. e.g.
12
Glucose - Galactose – Mannose - Fructose
CLASSIFICATION OF MONSACCHARIDES
2.
According to the characteristic carbonyl group (aldehyde
or ketone group):
A-Aldoses: monosacchrides containing aldehyde
group e.g. Glucose, galactose, ribose, and
glyceraldehyde
B- Ketoses: monosaccharides containing ketone group
e.g. Fructose, ribulose and dihydroxy acetone
•
•
•
Sometimes Combination of 1 and 2 e.g.
Glucose is Aldohexose: a six-carbon monosaccharide
(hexose) containing an aldehyde group (Aldose).
Fructose is Ketohexose: a six-carbon monosaccharide
(hexose) containing a ketone group (Ketose).
13
Monosaccharides
•Classification according to the characteristic carbonyl group
14
Monosaccharides
•The simplest aldose is glyceraldehyde.
•The simplest ketose is dihydroxyacetone.
•They are constitutional isomers of each other,
sharing the formula C3H6O3.
15
H C O
CH2OH
H C OH
C O
HO C H
HO C H
H C OH
H C OH
H C OH
H C OH
CH2OH
CH2OH
Glucose (an Aldose)
Fructose (a Ketose)
16
1
O
1
O
1
C H
2
H C OH
C H
C H
C H
H 2C OH
H 2C OH
H 3C OH
1
O
H
3C
OH
3CH OH
2
4CH OH
2
D- Glyceraldehdye
D-Erythrose
H
4C
O
OH
5
CH2OH
D-Ribose
H 2C OH
HO 3C H
H 4C OH
5
H C OH
6
CH2OH
D-Glucose
Examples of Aldoses of physiologic significance
17
1
1
CH2OH
1CH OH
2
2C
O
O
H 3 C OH
H 3C OH
H 4C OH
2C
4
5
CH2OH
D-Erythrulose
CH2OH
D-Ribulose
1
CH2OH
CH2OH
2C
O
HO 3 C H
H 4C OH
5
CH2OH
D-Xylulose
2C
O
HO 3 C H
H 4C OH
H 5 C OH
6
CH2OH
D-Fructose
Examples of Ketoses of physiologic significance
18
•Glucose is the most important sugar for living organisms.
•It has one carbonyl group (aldehyde) and five hydroxy groups (Alcohol). The
OH groups can be distributed either at the right side (D; 2,4,5,6) or left side
(L; 3). Glucose is named as D or L according to the orientation of C-5
•In reality, C1 (CHO) and C5 (OH) react together so that glucose forms a ring.
OH at the right side becomes down (alpha = ) and that on the left becomes
up (beta = b)
O
H

C
H
C
OH
HO C
H
H
C
OH
H
C
OH
1

CH2OH
D-Glucose
6
6
-D-Glucose
-D-Glucose
(-D-Glucopyranose)
b
1
b-D-Glucose
(b-D-Glucopyranose)
19
Fischer Projection
Haworth Projection
BIOMEDICALLY, GLUCOSE IS THE MOST IMPORTANT MONOSACCHARIDE
α-D-glucose chair form
Straight chain form
α-D-glucose
Haworth projection
Fischer projection formulas
Pyranose and Furanose forms of Glucose
Glucose in solution, more than 99% is in the pyranose form
20
Monosaccharides have a aldehyde/ketone and an
alcohol in the same molecule In the same molecule,
so it forms an intramolecular hemiacetal linkage
21
Haworth Formula of Sugars
6
CH2 OH
O
O
5
H
H
HO
4
HO
O
3
OH
2
OH
 -D- Glucopyranose
6
1
CH2OH O
5
H
H
4
HO
Furan ring
1
H
H
Pyran ring
H
OH
CH2 OH
2
OH
3
H
-D-Fructofuranose
22
Pyranose
Furanose
23
Anomerism
•C-1 in the cyclic structure is called
anomeric carbon atom.
•It is asymmetric C atom.
•If the –OH at C-1 (the anomeric carbon) is
to the right it is called -Form.
•If the –OH at C-1 is to the left it is called bform.
24
Anomerism
H
1
C
1
2
3
HO C H
H
4
5
H C OH
O
3
HO C H
C OH
H
C
H
6
- D-Glucose CH2OH
C
2
H C OH
H
H
HO
OH
4
5
O
C OH
C
6
CH2OH b- D-Glucose
25
- and b- forms of sugars are called anomers (a type of stereoisomerism)
Isomerism
• Isomers are chemical compounds having the
same molecular formula but different
structural or stereochemical formula.
• Functional group isomerism (e.g. Aldose
Ketose
isomerism):
Glucose
and
Fructose are aldose-ketose isomers
• Also,
Glyceraldehyde
and
Dihydroxyaxetone
are
aldose-ketose
26
isomers
Glycosidic Bond
• Glycosides are formed by reaction
between hemiacetal or hemiketal hydroxyl
group of carbohydrate react with hydroxyl
group of another carbohydrate or noncarbohydrate alcohol group. The bond
formed is known as glycosidic bond
How glucose molecules join together
Two glucose molecules
are linked by a
condensation reaction.
this results in the
formation of a
disaccharide called
maltose. The two
monosaccharides are
linked by a glycosidic
bond (c-o-c ) and the
molecules share an
oxygen atom. During the
condensation reaction
water is formed.
Disaccharides
• Disaccharides are made up of two
monosaccharide of same unit or different
• 1 Maltose ----- Glucose + Glucose
Maltose
Characteristic malt flavour
End product of enzymatic
degradation of starch &
glycogen by amylase
Shows mutarotation,
fermentable, water soluble
•
Lactose ---------Glucose+Galactose
Lactose
Characteristic of milk – 4.4-5.2 %
D-glucose+D-galactose
Hydrolyzed by latase & strong acids
•
Sucrose ----------Glucose + Fructose
Disaccharides
sucrose
lactose
Polysaccharides
• Polysaccharides are polymer of
monosaccharides of same type or different
type
• Classification according to biological role:
– Storage polysaccharides (starch, glycogen)
– Structural polysaccharides (cellulose, chitin)
• Classification according to no of types of
monosaccharides:
– homoglycans / heteroglycans
Polysaccharides
• They do not have sweet taste
• They are amorphous substance insoluble
in water
• They have high molecular weight
• They form colloidal solutions when heated
with water
• they don not exhibit any of the properties
of aldehyde or keto groups
Homopolysaccharides They contain monosaccharides
units of a single type
e.g Glycogen, starch, cellulose, chitin
The polymer of α-glucose is starch
The polymer of β-glucose is cellulose
Polysaccharides
•
Heteopolysaccharides They possess
two or more types monosaccharides
units or their derivatives e.g Heparin,
Chondroitin, Hyaluronic acid
Polysaccharides
Cellulose
• it is a non sugar and homopolysaccharide
since only it is composed of glucose units
• it is not easily hydrolyzed . It is hydrolyzed
to glucose by conc. H2So4 or NaOH
• it is main constituent of cell walls of plants
• it occurs in lignin and cotton
• its mol. wt. ranges from 2,00,000 to
20,00,000 Da
• it contains 1,200 to 12,500 glucose units
per molecules
• Glucose units are linked by β1,4glycosidic bond.
• It is not nutritive because of its inertness
towards chemical reaction
• Cellulose is not digested by man
• Ruminants like cattle, sheep, goats, camel
and certain wood eating insects able to
digest cellulose due to presence of
cellulase enzyme in their digestive tract
Cellulose
• Forms chains which run parallel with
hydrogen bonds between the chains to
form microfibrils
• Microfibrils are strong
• Being fibrous, cellulose is structurally
important in plant cell walls
Cellulose
• Polymer of β-glucose
• Each monomer is
inverted.
• Has consequences for
its properties
Starch.
• It is a homopolysaccharide.
• It is a non-sugar
• It yields glucose on complete hydrolysis. So it is
a glucan.
• It is the main storage material in plants. starch is
insoluble and compact , but it is easily available
for use by the plant.
• It is a white amorphous, tasteless and soft
substance.
• it is made up of glucose units. The glucose units are
arranged in the form of branched and un branche
chains.
• The glucose units are linked by α-1, 4-glycosidic
linkages and branches are formed by α-1, 6-glycosidic
bond.
• Starch consists of two compounds:
1. Amylose (20%) –this is made up of a single chain
of α glucose molecules that form spirals.
2. Amylopectin (80%) - this is made up of branched
chains of α glucose.
Structure of starch
Starch
α-Amylose
Amylose
• it is a homopolysaccharide with a Mol. Wt.
ranging from 10,000 to 50,000 Da
• It is a water soluble.
• It has a long unbranched straight chain –
made up of glucose units.
• the amylose chain is in the form of helix;
each turn has 6 glucose units.
• the enzyme amylase converts amylose
into maltose.
• it gives intense blue colour with iodine
Amylopectin
• it is a homopolysaccharide with high Mol.
Wt.
• It is insoluble in water.
• It is a branched chain – made up of
glucose units (2,000 to 2,00,000 units).
• It gives isomaltose during hydrolysis.
• it gives purple colour with iodine
Amylopectin.
Glycogen.
• Glycogen is the main storage
carbohydrate in animals.
• It has a similar structure to amylopectin,
but it has more branches.
• It structure allows it to be quickly built up
or broken down , matching the animals
needs.
•Glycogen is a homopolysaccharide since it gives glucose on
complete hydrolysis. It is a glucan.
• It is the major reserve carbohydrate in animals. So it is called as
ANIMAL STARCH.
•It is stored mainly in the liver and muscles of animals. Among
plants it is found in fungi and yeast which are devoid of chlorophyll.
•It is a white powder. It readily dissolves in water.
•It gives red colour with iodine.
•It is a branched polymer of glucose with α-1,4and α-1,6 types of
linkages.
•The straight chain contains α-1,4- glycosidic bond. The point of
branching contains 1,6- glycosidic bond.
•It is a non reducing sugar. It gives red colour with
iodine. The red colour disappears on boiling and
reappears on cooling.
•The liver glycogen supplies glucose to all tissues
through the blood.
•The blood always contains 1% glucose. When it
exceeds 1%,the excess glucose is transported to the
liver and is converted into glycogen.
•When blood sugar level is below 1% the liver glycogen
is changed into blood glucose.
•Muscle glycogen is utilized as the energy source
during muscle contraction.
•Glycogen resembles amylopectin of starch chemically
but differs from it in molecular weight and degree of
branching.
CHITIN
•Chitin is an important polysaccharide of invertebrates.
•It is formed of many units of N-ACETYL GLUCOSAMINE
linked by β-1,4- linkage.
•It is related to cellulose. The alcoholic OH group on
carbon atom 2 of β-D-glucose units is replaced by Nacetylamino group.
•It is found in the exoskeleton of insects and
crustaceans and in the cell walls of fungi.
•On hydrolysis with mineral acids it gives
glucosamine and acetic acid.
•Chitin is decomposed to N-acetyl glucosamine
by CHITINASE present in the gastric juice of
snails or from bacteria.
DEXTRIN
•Dextrins
are
a
group
of
low-molecularweight
carbohydrates
produced
by
the hydrolysis of starch[1] or glycogen.[2] Dextrins are
mixtures of polymers of D-glucose units linked by α(1→4) or α-(1→6) glycosidic bonds.
•Dextrins
can
be
produced
from
starch
using enzymes like amylases, as during digestion in the
human body and during malting andmashing,[3] or by
applying
dry
heat
under
acidic
conditions
(pyrolysis or roasting).
•Used industrially on the surface of bread during the
baking process, contributing to flavor, color, and
crispness. Dextrins produced by heat are also known
as pyrodextrins.
• Dextrins are white, yellow, or brown powders that are
partially or fully water-soluble, yielding optically
active solutions of low viscosity. Most can be detected
with iodine solution, giving a red coloration; one
distinguishes erythrodextrin (dextrin that colours red)
and achrodextrin (giving no colour).
•White and yellow dextrins from starch roasted with little
or no acid is called British gum.
•Sephadex is a trademark for cross-linked dextran gel used
for gel filtration.
• It is normally manufactured in a bead form and most
commonly used for gel filtration columns. By varying the
degree of cross-linking, the fractionation properties of the gel
can be altered.
•These highly specialized gel filtration
and chromatographic media are composed of macroscopic
beads synthetically derived from the polysaccharide, dextran.
The organic chains are cross-linked to give a threedimensional network having functional ionic groups attached
by ether linkages to glucose units of the polysaccharide
chains.
GLYCOPROTEINS
• Glycoproteins are proteins that
contain oligosaccharide chains
(glycans) covalently attached to polypeptide sidechains.
• The carbohydrate is attached to the protein in a cotranslational or post-translational modification.
• This process is known as glycosylation. Secreted
extracellular proteins are often glycosylated.
• Glycoproteins are often important integral
membrane proteins, where they play a role in cell–
cell interactions.
There are two types of
glycosylation:
• In N-glycosylation, the addition of sugar
chains can happen at the amide nitrogen
on the side-chain of the asparagine.
•
In O-glycosylation, the addition of sugar
chains can happen on
the hydroxyl oxygen on the side-chain
of hydroxylysine, hydroxyproline, serine,
or threonine
• Glycoproteins are important for white blood cell recognition,
especially in mammals.
• molecules such as antibodies (immunoglobulins), which
interact directly with antigens are glycoproteins.
• molecules of the major histocompatibility complex (or
MHC), which are expressed on the surface of cells and
interact with T cells as part of the adaptive immune
response.
• glycoprotein IIb/IIIa, an integrin found on platelets that is
required for normal platelet aggregation and adherence to
the endothelium.
• components of the zona pellucida, which surrounds
the oocyte, and is important for sperm-egg interaction.
GLYCOSAMINOGLYCANS
• Glycosaminoglycans (GAGs) are long
unbranched polysaccharides consisting of a repeating
disaccharide unit.
• The repeating unit consists of an amino sugar (Nacetylglucosamine or N-acetylgalactosamine) along with
a uronic sugar (glucuronic acid or iduronic acid)
or galactose.
• Glycosaminoglycans are highly polar and attract water.
• They are therefore useful to the body as a lubricant or as
a shock absorber.
2. Glycosaminoglycans
CHONDROTIN – 4- SULPHATE
• In chondratin – 4 – sulphate the two
repeating monosaccharide derivatives are
GlcA & GALNAC6S.
• It contributes to the tensile strength of
cartilage, tendons and ligaments.
HEPARIN
• Heparin is a natutal coagulant that is
prepared in mast cells and then released
into blood.
• It inhibits blood coagulation by binding to
the protein anti- thrombin.
• Purified heparin is added to blood samples
obtained for clinical analysis and to the
blood.
LECTINS
Lectins
are
carbohydrate-binding
proteins,
macromolecules that are highly specific for
sugar moieties. Lectins should neither be confused
with glycoproteins (proteins containing sugar chains or
residues), lecithins (fatty substances in animals and
plants), nor leptin (the regulator of appetite and
hunger, metabolism, and behavior).
Long before a deeper understanding of their numerous
biological functions, the plant lectins, also known
as phytohemagglutinins, were noted for their particular
high specificity for foreign glycoconjugates (e.g. those
of fungi, invertebrates, and animals).[1] and used in
biomedicine for blood cell testing and in biochemistry
for fractionation.
Lectins perform recognition on the cellular and
molecular level and play numerous roles in biological
recognition phenomena involving cells, carbohydrates,
and proteins. Lectins also mediate attachment and
binding of bacteria and viruses to their intended
targets. For example, it is hypothesized that
some hepatitis C viral glycoproteins attach to C-type
lectins on the host cell surface (liver cells) for infection.
Lectins
may
be
disabled
by
specific
mono-
and oligosaccharides, which bind to ingested lectins from
grains, legume, nightshade plants and dairy; binding can
prevent their attachment to the carbohydrates within the
cell membrane. Some lectins may be powerful toxins as
for instance ricin, and others have been incorporated
into genetically engineered crops to transfer traits, such
as resistance to pests and resistance to herbicides.
Mutarotation
• interconversion of α- and β- anomers
•The α- and β- anomers of carbohydrates are typically
stable solids.
•However, in aqueous solution, they quickly equilibrate to
an equilibrium mixture of the two forms.
•For example, in aqueous solution, glucose exists as a
mixture of 36% α- and 64% β- (>99% of the pyranose
forms exist in solution).