LECTURE 3 –STRUCTURE AND LECTURE 3 –STRUCTURE AND PROPERTIES OF PROPERTIES OF

CARBOHYDRATESCARBOHYDRATES• Structure, properties and function of Structure, properties and function of carbohydrates and their derivativescarbohydrates and their derivatives• Classification of carbohydratesClassification of carbohydrates

Course outcome:Course outcome:• Ability to differentiate basic structure, Ability to differentiate basic structure, properties, functions and classification properties, functions and classification of important biomolecules.of important biomolecules.

LECTURE 3 -CARBOHYDRATESLECTURE 3 -CARBOHYDRATES

TOPICS:TOPICS:

1.1. Role & Significance of Role & Significance of CarbohydratesCarbohydrates

2.2. MonosaccharideMonosaccharide

3.3. OligosaccharidesOligosaccharides

4.4. PolysaccharidesPolysaccharides

Section

Section

Section

Section

Sect.1. ROLE OF CARBOHYDRATESSect.1. ROLE OF CARBOHYDRATES

As a major energy source for living As a major energy source for living organisms organisms (glucose is a principal energy source in animal and plants)(glucose is a principal energy source in animal and plants)

As a means of transporting energy As a means of transporting energy ( exp: ( exp:

sucrose in plant tissues)sucrose in plant tissues)

As a structural material As a structural material ( cellulose in plants, chitin in insects, ( cellulose in plants, chitin in insects,

building blocks of nucleotides)building blocks of nucleotides)..As a precursor for other biomolecules As a precursor for other biomolecules (purine, pyrimide) (purine, pyrimide)

Sect 1. SIGNIFICANCE OF CARBOHYDRATESSect 1. SIGNIFICANCE OF CARBOHYDRATES

Carbohydrates are the most abundant Carbohydrates are the most abundant biomolecules in nature, having a direct link biomolecules in nature, having a direct link between solar energy and the chemical bond between solar energy and the chemical bond energy in living organisms.energy in living organisms.

Source of rapid energy productionSource of rapid energy production

Structural building blocks of cellsStructural building blocks of cells

Components of several metabolic pathwaysComponents of several metabolic pathways

Recognition of cellular phenomena, such as cell Recognition of cellular phenomena, such as cell recognition and binding (e.g., by other cells, recognition and binding (e.g., by other cells, hormones, and viruses)hormones, and viruses)

Carbohydrate : compounds contains H, C & O with the Carbohydrate : compounds contains H, C & O with the comp : (CHcomp : (CH22O)O)nn (Hydrate of carbon) (Hydrate of carbon)

Carbohydrates : Carbohydrates : Consist of sugar (saccharum)Consist of sugar (saccharum)Sugars : Sugars : compound that contains alcohol & carbonyl compound that contains alcohol & carbonyl

functional groupfunctional group

Carbonyl func.group : >C=oCarbonyl func.group : >C=o

Adehyde Adehyde aldose aldose

Ketone Ketone ketose ketose

CARBOHYDRATESCARBOHYDRATES

Examples:Examples:

cellulose, chitin, cellulose, chitin, starch, glycogen, starch, glycogen, glucoaminoglycansglucoaminoglycans

disaccharidesdisaccharides GlycoproteinsGlycoproteins (bacterial cell (bacterial cell wallswalls

ClassificationClassification

Carbohydrate

Mono Mono saccharidesaccharide

OligoOligosaccharidesaccharide

PolyPolysaccharidesaccharide GlyconoconjugatesGlyconoconjugates

Glucose, fructoseRibose (aldopentose)Deoxy ribose

glycoproteins and proteoglycans

Sect2.Sect2.

MONOSACHARIDESMONOSACHARIDES

Sect. 2. MonosacharidesSect. 2. Monosacharides

Sub sections :Sub sections :2.1 Properties & classification 2.1 Properties & classification 2.2 Stereoisomers2.2 Stereoisomers2.3 Cyclic structure2.3 Cyclic structure2.4 Important Reactions2.4 Important Reactions2.5 Important monosach2.5 Important monosach2.6 2.6 glycoproteinsglycoproteins and and proteoglycansproteoglycans2.7 2.7 Monosaccharide derivatives

2.1 Monosach Properties& classification2.1 Monosach Properties& classification

Colorless, crystalline solidsSSoluble in water but insoluble in nonpolar solventsOne of the carbon atoms is double-bonded to an oxygen atom to form a carbonyl group; each of the other carbon atoms has a hydroxyl group.– Carbohydrates with an aldehyde (-CHO) functional Carbohydrates with an aldehyde (-CHO) functional

group are called group are called aldoses aldoses e.g. glyceraldehyde (CHe.g. glyceraldehyde (CH22OH-CHOH-OH-CHOH-CHOCHO))

Those with a keto group (-C=O) are Those with a keto group (-C=O) are ketosesketoses e.g.dihydroxyacetone (CH2OH-e.g.dihydroxyacetone (CH2OH-C=OC=O-CH2OH)-CH2OH)

– Classified according to the number of carbon atoms Classified according to the number of carbon atoms they containthey contain

Monosacharides : Exp. aldoses & ketosesMonosacharides : Exp. aldoses & ketoses

AldotetroseAldotrioseAldopentoses

Ketotriose Ketotetrose Ketopentose Ketohexose

Aldohexose

2.2. MONOSACCHARIDES 2.2. MONOSACCHARIDES STEREOISOMERSSTEREOISOMERS

Isomers: same chemical formulas, different structures

Total no of possible isomers can be determined by Van Hoff’s rule: Total no of possible isomers can be determined by Van Hoff’s rule: compound with n chiral C atoms has a max of 2n possible compound with n chiral C atoms has a max of 2n possible stereoisomers. stereoisomers.

Chiral: Chiral: asymmetric carbons, i.e carbon atom with four different substituents

Eg: n = 4, there are 16 stereoisomers (8-L stereoisomers, 8-D Eg: n = 4, there are 16 stereoisomers (8-L stereoisomers, 8-D stereoisomers).stereoisomers).

In optical isomers- the ref C is the asymmetric C that is most remote In optical isomers- the ref C is the asymmetric C that is most remote from the C=O carbon.from the C=O carbon.

In D-aldose family sugars, the OH group is to the right on the chiral In D-aldose family sugars, the OH group is to the right on the chiral C atom farthest from the most oxidized C (aldehyde group) in the C atom farthest from the most oxidized C (aldehyde group) in the molecule. molecule.

D- and L- enantiomersD- and L- enantiomers

Stereoisomers that are not enantiomers Stereoisomers that are not enantiomers (mirror-image) are called (mirror-image) are called diastereoisomersdiastereoisomers..

Eg: aldopentoses, D-ribose and L-ribose Eg: aldopentoses, D-ribose and L-ribose are enantiomers.are enantiomers.

The D-ribose and D-arabinose are The D-ribose and D-arabinose are diastereomers because they are isomers diastereomers because they are isomers but not mirror image. but not mirror image.

Diastereomers that differ in the Diastereomers that differ in the configuration at a single asymmetric C configuration at a single asymmetric C atom are called atom are called epimersepimers..

Eg: D-glucose and D-galactose are Eg: D-glucose and D-galactose are epimers because they differ only in the epimers because they differ only in the configuration of the OH group at C-4. configuration of the OH group at C-4.

D-mannose and D-galactose are not D-mannose and D-galactose are not epimers- differ more than 1 C.epimers- differ more than 1 C.

2.2. MONOSACCHARIDES STEREOISOMERS2.2. MONOSACCHARIDES STEREOISOMERSThe simplest aldose, glyceraldehyde, contains one chiral center (the middle carbon atom) and has two different optical isomers, or enantiomers

the projection in which the carbohydrate backbone is the projection in which the carbohydrate backbone is

drawn vertically with the carbonyl shown on the top.drawn vertically with the carbonyl shown on the top.

2.3 Cyclic structure of monosacharides2.3 Cyclic structure of monosacharides• in aqueous solution, monosaccharides with five or more carbon atoms in the backbone occur predominantly as cyclic (ring) structures in which the carbonyl group has formed a covalent bond with the oxygen of a hydroxyl group along the chain.• Sir Norman Haworth showed that the linear form of glucose (and other aldohexose) could undergo intramolecular reaction to form a cyclic hemiacetal. • the analogous intramolecular reaction of ketose sugar yields a cyclic hemiketal.

The new chiral center in cyclic (c1) is called anomeric carbon

In aldose sugars, the OH group of the newly In aldose sugars, the OH group of the newly formed hemiacetal occurs on C-1 (the formed hemiacetal occurs on C-1 (the anomericanomeric carbon).carbon).

The OH group may occur either below the ring The OH group may occur either below the ring ((downdown position)- position)- αα-anomeric -anomeric form.form.

Or above the ring (Or above the ring (upup position)- position)-ββ -anomeric -anomeric form.form.

In Fischer projections, the In Fischer projections, the αα–anomeric OH –anomeric OH occurs on the occurs on the rightright and and ββ–anomeric OH occurs –anomeric OH occurs on the on the leftleft..

Pyranoses& FuranosesPyranoses& Furanoses

Pyranoses: six-membered ring compounds ( resemble pyran )Furanoses : fivemembered rings, (resemble furan)

The structure systematic names glucose & fructose become

An English chemist W.N. An English chemist W.N. Haworth gave a more accurate Haworth gave a more accurate picture of carbohydrate picture of carbohydrate structure. structure.

HAWORTH STRUCTURESHAWORTH STRUCTURES

Haworth StructuresHaworth StructuresTo convert from traditional Fischer formula of a D-pentose To convert from traditional Fischer formula of a D-pentose or D-hexose to a Haworth formula, the following steps or D-hexose to a Haworth formula, the following steps should be followed:should be followed:

Draw a 5 or 6-membered ring with the O placed as shown Draw a 5 or 6-membered ring with the O placed as shown below:below:

Starting with anomeric carbon to the right of the ring O, place Starting with anomeric carbon to the right of the ring O, place OH group either above or below the plane of the ring. OH group either above or below the plane of the ring. Group that pointing to the left in Fischer projection should Group that pointing to the left in Fischer projection should go above (go above (ββ-) the plane of the ring, and those pointing right -) the plane of the ring, and those pointing right should go below the ring (should go below the ring (αα-)-)

In D-sugars, the last C position (eg: C-6 glucose) is always In D-sugars, the last C position (eg: C-6 glucose) is always upup

FISHER AND HAWORTH FORMS OF SUGARFISHER AND HAWORTH FORMS OF SUGAR

SUMMARY OF SUGAR STRUCTURESSUMMARY OF SUGAR STRUCTURES

ISOMERS- compounds that have the same chemical formula e.g. ISOMERS- compounds that have the same chemical formula e.g. fructose, glucose, mannose, and galactose are isomers of each fructose, glucose, mannose, and galactose are isomers of each other having formula Cother having formula C66HH1212OO66..EPIMERS- refer to sugars whose configuration differ around one EPIMERS- refer to sugars whose configuration differ around one specific carbon atom e.g. glucose and galactose are C-4 epimers specific carbon atom e.g. glucose and galactose are C-4 epimers and glucose and mannose are C-2 epimers.and glucose and mannose are C-2 epimers.ENANTIOMERS- a special type of isomerism found in pairs of ENANTIOMERS- a special type of isomerism found in pairs of structures that are mirror images of each other. The mirror images structures that are mirror images of each other. The mirror images are termed as enantiomers and the two members are designated as are termed as enantiomers and the two members are designated as D- and L- sugar. The vast majority of sugars in humans are D-D- and L- sugar. The vast majority of sugars in humans are D-sugars.sugars.CYCLIZATION OF SUGARS- most monosaccharides with 5 or CYCLIZATION OF SUGARS- most monosaccharides with 5 or more carbon atoms are predominately found in a ring form, where more carbon atoms are predominately found in a ring form, where the aldehyde or ketone group has reacted with an alcoholic group the aldehyde or ketone group has reacted with an alcoholic group on the same sugar group to form a on the same sugar group to form a hemiacetalhemiacetal or or hemiketal hemiketal ring.ring.

PyranosePyranose ring- if the ring has 5 carbons and 1 oxygen. ring- if the ring has 5 carbons and 1 oxygen. Furanose Furanose ring- if the ring is 5-membered (4 carbons and 1 oxygenring- if the ring is 5-membered (4 carbons and 1 oxygen

2.4.IMPORTANT REACTIONS IN MONOSACCHARIDES2.4.IMPORTANT REACTIONS IN MONOSACCHARIDES

Monosaccharides undergo the following reactions :Monosaccharides undergo the following reactions :

1.1. MutarotationMutarotation2.2. OxidationOxidation3.3. ReductionReduction4.4. IsomerizationIsomerization5.5. EsterificationEsterification6.6. Glycoside formationGlycoside formation

1.1. MutarotationMutarotation – – alfaalfa and and betabeta forms of sugars are readily interconverted when forms of sugars are readily interconverted when dissolved in water. Mutarotation produces an equilibrium mixture of dissolved in water. Mutarotation produces an equilibrium mixture of αα and and ββ- forms in both furanose and pyranose ring structures. - forms in both furanose and pyranose ring structures.

22 Oxidation and reduction Oxidation and reduction in presence of oxidising agents, metal ions (Cu2+) and enzymes, in presence of oxidising agents, metal ions (Cu2+) and enzymes, monosacchs undergo several oxidation reactions e.g. Oxidation of monosacchs undergo several oxidation reactions e.g. Oxidation of aldehyde group (R-CHO) yields aldonic acid; of terminal CH2OH aldehyde group (R-CHO) yields aldonic acid; of terminal CH2OH (alcohol) yields uronic acid; and of both the aldehyde and CH2OH (alcohol) yields uronic acid; and of both the aldehyde and CH2OH gives aldaric acid. The carbonyl groups in both aldonic and uronic gives aldaric acid. The carbonyl groups in both aldonic and uronic can react with an OH group in the same molecule to form a cyclic can react with an OH group in the same molecule to form a cyclic ester known as a lactone.ester known as a lactone.

sugars that can be oxidized by weak oxidizing agent ie. Benedict’s sugars that can be oxidized by weak oxidizing agent ie. Benedict’s reagent, called reducing sugars. Because the reaction occurs only reagent, called reducing sugars. Because the reaction occurs only with sugars that can revert to open chain form, all with sugars that can revert to open chain form, all monosaccharides are reducing sugars. monosaccharides are reducing sugars.

IMPORTANT REACTIONS IN MONOSACCHARIDESIMPORTANT REACTIONS IN MONOSACCHARIDESDetailsDetails

3.3. REDUCTION REDUCTIONreduction of the aldehyde and ketone reduction of the aldehyde and ketone groups of monosacchs yield sugar groups of monosacchs yield sugar alcohols (alditols) Sugar alcohols alcohols (alditols) Sugar alcohols e.g.sorbitol, are used commercially in e.g.sorbitol, are used commercially in processing foods and pharmaceuticals.processing foods and pharmaceuticals.

sorbitol- improves the shelf-life of candy- sorbitol- improves the shelf-life of candy-

it helps prevent moisture loss.it helps prevent moisture loss.

IMPORTANT REACTIONS (Cont)IMPORTANT REACTIONS (Cont)

4.4. ISOMERIZATION ISOMERIZATION Monosaccharides undergo several types of isomerization e.g. D-glucose in Monosaccharides undergo several types of isomerization e.g. D-glucose in alkaline solution for several hours contain D-mannose and D-fructose. Both alkaline solution for several hours contain D-mannose and D-fructose. Both isomerization involves an intramolecular shift of a H atom and a relocation isomerization involves an intramolecular shift of a H atom and a relocation of double bond. The conversion of glucose to mannose is termed s of double bond. The conversion of glucose to mannose is termed s epimerizationepimerization. .

55 ESTERIFICATIONESTERIFICATIONFree OH groups of carbohydrates react with acids to form Free OH groups of carbohydrates react with acids to form estersesters. This . This reaction an change the physical and chemical propteries of sugar.reaction an change the physical and chemical propteries of sugar.

6.6. GLYCOSIDE FORMATION- GLYCOSIDE FORMATION- Hemiacetals and hemiketals reaction with alcohols to form the Hemiacetals and hemiketals reaction with alcohols to form the corressponding aceta or ketal. On the contrary when a corressponding aceta or ketal. On the contrary when a cycliccyclic hemiacetal or hemiacetal or hemiketal form of monosaccharide reacts with alcohol, the new linkage is hemiketal form of monosaccharide reacts with alcohol, the new linkage is called called glycosidic linkageglycosidic linkage and the compound and the compound glycoside.glycoside.

Alfa & beta GLYCOSIDIC BONDAlfa & beta GLYCOSIDIC BOND

REDUCING SUGARSREDUCING SUGARS

All monosacchs are reducing sugars.All monosacchs are reducing sugars.They can be oxidised by weak oxidising They can be oxidised by weak oxidising agent such as Benedict’s reagentagent such as Benedict’s reagentBenedict's reagent is a solution of copper Benedict's reagent is a solution of copper sulfate, sodium hydroxide, and tartaric sulfate, sodium hydroxide, and tartaric acid. acid.

Aqueous glucose is mixed with Benedict's reagent and heated. Aqueous glucose is mixed with Benedict's reagent and heated. The reaction reduces the blue copper (II) ion to form a brick red The reaction reduces the blue copper (II) ion to form a brick red precipitate of copper (I) oxide. Because of this, glucose is precipitate of copper (I) oxide. Because of this, glucose is

classified as a reducing sugarclassified as a reducing sugar. .

2.5 IMPORTANT MONOSACCHARIDES

GLUCOSE GLUCOSE FRUCTOSEFRUCTOSEGALACTOSEGALACTOSE

D-Glucose:D-Glucose:D-glucose (dextrose) is the primary fuel in living cells especially in brain cells that have few or no mitochondria.

Cells such as eyeballs have limited oxygen supply and use large amount of glucose to generate energy

Dietary sources include plant starch, and the disaccharides lactose, maltose, and sucrose

Important monosaccharides. Cont

FRUCTOSE FRUCTOSE – D-fructose (levulose) is often referred as fruit sugar D-fructose (levulose) is often referred as fruit sugar

and is found in some vegetables and honeyand is found in some vegetables and honey– This molecule is an important member of ketose This molecule is an important member of ketose

member of sugarsmember of sugars– It is twice as sweet as sucrose (per gram basis) and It is twice as sweet as sucrose (per gram basis) and

is used as sweeting agent in processed food productsis used as sweeting agent in processed food products– It is present in large amounts in male reproductive It is present in large amounts in male reproductive

tract and is synthesised in the seminal vesicles.tract and is synthesised in the seminal vesicles.

Important monosaccharides. Cont....Important monosaccharides. Cont....

GALACTOSE GALACTOSE – is necessary to synthesize a variety of biomolecules is necessary to synthesize a variety of biomolecules

((lactoselactose-in mammalary glands, -in mammalary glands, glycolipidsglycolipids, certain , certain phospholipidsphospholipids, , proteoglycansproteoglycans, and , and glycoproteinsglycoproteins))

– Galactose and glucose are epimers at carbon 4 and Galactose and glucose are epimers at carbon 4 and interconversion is catalysed by enzyme interconversion is catalysed by enzyme epimeraseepimerase..

– Medical problems – Medical problems – galactosemiagalactosemia (genetic disorder) (genetic disorder) where enzyme to metabolize galactose is missing; where enzyme to metabolize galactose is missing; accumulation of galactoseaccumulation of galactose in the body can cause in the body can cause liver liver damagedamage, , cataractscataracts, and severe , and severe mental retardationmental retardation

2.7.MONOSACCHARIDE DERVATIVES

URONIC ACIDS – formed when terminal URONIC ACIDS – formed when terminal CHCH22OH group of a mono sugar is oxidisedOH group of a mono sugar is oxidised

– Important acids in animals – D-glucuronic acid Important acids in animals – D-glucuronic acid and its epimer L-iduronic acidand its epimer L-iduronic acid

– In liver cells glucuronic acid combines with In liver cells glucuronic acid combines with steroids, certain drugs, and bilirubin to steroids, certain drugs, and bilirubin to improve water solubility therby helping the improve water solubility therby helping the removal of waste products from the bodyremoval of waste products from the body

– These acids are abundant in the connective These acids are abundant in the connective tissue carbohydrate components.tissue carbohydrate components.

Mono sugar derivatives

AMINO SUGARS –AMINO SUGARS –– Sugars in which a hydroxyl group (common Sugars in which a hydroxyl group (common

on carbon 2) is replaced by an amino group on carbon 2) is replaced by an amino group e.g. D-glucosamine and D-galactosaminee.g. D-glucosamine and D-galactosamine

– common constituents of complex common constituents of complex carbohydrate molecule found attached to carbohydrate molecule found attached to cellular proteins and lipidscellular proteins and lipids

– Amino acids are often acetylated e.g. N-Amino acids are often acetylated e.g. N-acetyl-glucosamine.acetyl-glucosamine.

Mono sugar derivatives

DEOXYSUGARS DEOXYSUGARS – monosaccharides in which an - H has replaced an – monosaccharides in which an - H has replaced an –

OH groupOH group– Important sugars: L-fucose (formed from D-mannose Important sugars: L-fucose (formed from D-mannose

by reduction reactions) and 2-deoxy-D-riboseby reduction reactions) and 2-deoxy-D-ribose– L-fucose – found among carbohydrate components of L-fucose – found among carbohydrate components of

glycoproteins, such as those of the ABO blood group glycoproteins, such as those of the ABO blood group determinates on the surface of red blood cellsdeterminates on the surface of red blood cells

– 2-deoxyribose is the pentose sugar component of 2-deoxyribose is the pentose sugar component of DNA.DNA.

GLYCOSIDIC BONDSGLYCOSIDIC BONDS• Monosaccharides Monosaccharides can be linked by glycosidic bonds can be linked by glycosidic bonds

(joining of 2 hydroxyl groups of sugars by splitting out (joining of 2 hydroxyl groups of sugars by splitting out water molecule) to create larger structures.water molecule) to create larger structures.

• Disaccharides Disaccharides contain 2 monosaccharides e.g. lactose contain 2 monosaccharides e.g. lactose (galactose+glucose); maltose (glucose+glucose); (galactose+glucose); maltose (glucose+glucose); sucrose (glucose+fructose)sucrose (glucose+fructose)

• OligosaccharidesOligosaccharides – 3 to 12 monosaccharides units – 3 to 12 monosaccharides units e.g. glycoproteinse.g. glycoproteins

• Polysaccharides Polysaccharides – more than 12 monosaccharides – more than 12 monosaccharides units e.g. glycogen (units e.g. glycogen (homopolysaccharidehomopolysaccharide) having ) having hundreds of sugar units; glycosaminoglycans hundreds of sugar units; glycosaminoglycans ((heteropolysaccharidesheteropolysaccharides) containing a number of different ) containing a number of different monosaccharides speciesmonosaccharides species..

Section 3Section 3

DISACCHARIDES DISACCHARIDES

AND AND

OLIGOSACCHARIDESOLIGOSACCHARIDES

DISACCHARIDES AND DISACCHARIDES AND OLIGOSACCHARIDESOLIGOSACCHARIDES

Configurations: Configurations: alfaalfa or or betabeta ( 1,4, glycosidic bonds or ( 1,4, glycosidic bonds or linkages; other linkages 1,1; 1,2; 1,3; 1,6) linkages; other linkages 1,1; 1,2; 1,3; 1,6) Digestion of disaccharides and other carbohydrates Digestion of disaccharides and other carbohydrates aided by enzymes. Defficiency of any one enzyme aided by enzymes. Defficiency of any one enzyme causes unpleasant symptoms. The undigestible causes unpleasant symptoms. The undigestible dissacharide sugar pass into large intestine and digested dissacharide sugar pass into large intestine and digested by bacteria (by bacteria (fermentationfermentation) in colon produces gas ) in colon produces gas [bloating of cramps].[bloating of cramps].Most common defficiency, an ancestoral disorder, Most common defficiency, an ancestoral disorder, lactose intolerancelactose intolerance caused by reduced synthesis of caused by reduced synthesis of lactaselactase

Important sugars of DisaccharidesImportant sugars of Disaccharides LACTOSE LACTOSE

(milk sugar) disaccharide found in milk; composed of one molecule (milk sugar) disaccharide found in milk; composed of one molecule of galactose (OH group in C-1) and glucose (OH group at C-4) of galactose (OH group in C-1) and glucose (OH group at C-4) linked through linked through betabeta(1,4) glycosidic linkage (anomeric C of galactose (1,4) glycosidic linkage (anomeric C of galactose is in is in ββ-configurations); because of the hemiacetal group of the -configurations); because of the hemiacetal group of the glucose component, lactose is a reducing sugar glucose component, lactose is a reducing sugar

Lactose intoleranceLactose intolerance

Lactose (milk sugar) in infants is hydrolyzed by Lactose (milk sugar) in infants is hydrolyzed by intestinal enzyme lactase to its component intestinal enzyme lactase to its component monosacch for absorption into the bloodstream monosacch for absorption into the bloodstream (galactose epimerized to glucose). (galactose epimerized to glucose). Most adult mammals have low levels of beta-Most adult mammals have low levels of beta-galactosidase. Hence, much of the lactose they galactosidase. Hence, much of the lactose they ingest moves to the colon, where bacterial ingest moves to the colon, where bacterial fermentation generates large quantities of CO2, fermentation generates large quantities of CO2, H2 and irritating organic acids.H2 and irritating organic acids.These products cause painful digestive upset These products cause painful digestive upset known as known as lactose intolerancelactose intolerance and is common and is common in the African and Asian decent.in the African and Asian decent.

MALTOSE ( malt sugar)MALTOSE ( malt sugar)An intermediate product of starch hydrolysis; it is a disaccharide with an An intermediate product of starch hydrolysis; it is a disaccharide with an alfaalfa(1,4) (1,4) glycosidic linkage between two D-glucose molecules; in solution the free glycosidic linkage between two D-glucose molecules; in solution the free anomeric carbon undergoes mutarotation resulting in an equilibrium mixture of anomeric carbon undergoes mutarotation resulting in an equilibrium mixture of alfaalfa and and betabeta – maltoses; it does not occur freely in nature – maltoses; it does not occur freely in nature

SUCROSE SUCROSE common table sugar: cane sugar or beet sugar produced common table sugar: cane sugar or beet sugar produced in the leaves and stems of plants; it is a disaccharide in the leaves and stems of plants; it is a disaccharide containing both alfa-glucose and beta-fructose residues containing both alfa-glucose and beta-fructose residues linked by linked by alfa,betaalfa,beta(1,2)glycosidic bond.(1,2)glycosidic bond.

CELLOBIOSE CELLOBIOSE

degradation product of cellulose degradation product of cellulose containing two molecules of glucose linked containing two molecules of glucose linked by a by a betabeta (1,4) glycosidic bond; it does not (1,4) glycosidic bond; it does not occur freely in natureoccur freely in nature

OLIGOSACCHARIDE SUGARSOLIGOSACCHARIDE SUGARS

Oligosaccharides are small polymers often Oligosaccharides are small polymers often found attached to polypeptides in found attached to polypeptides in glycoproteinsglycoproteins and some and some glycolipidsglycolipids. .

They are attached to membrane and They are attached to membrane and secretory proteins found in endoplasmic secretory proteins found in endoplasmic reticulum and Golgi complex of various reticulum and Golgi complex of various cellscells

Two classes: N-linked and O-linkedTwo classes: N-linked and O-linked

Section 4Section 4POLYSACCHARIDESPOLYSACCHARIDES

4.1. Intro to Polysaccharides 4.1. Intro to Polysaccharides 4.2. Classification of Polisacharides4.2. Classification of Polisacharides4.2.1. Homosacharides4.2.1. Homosacharides4.2.2. 4.2.2. HeteropolysacharidesHeteropolysacharides

4.1. Intro to Polysaccharides4.1. Intro to Polysaccharides

Composed of large number of monosaccharide units Composed of large number of monosaccharide units connected by glycosidic linkagesconnected by glycosidic linkagesClassified on the basis of their main monosaccharide Classified on the basis of their main monosaccharide components and the sequences and linkages between components and the sequences and linkages between them, as well as the anomeric configuration of linkages, them, as well as the anomeric configuration of linkages, the ring size (furanose or pyranose), the absolute the ring size (furanose or pyranose), the absolute configuration (D- or L-) and any other substituents configuration (D- or L-) and any other substituents present. present. (http://www.lsbu.ac.uk/water/hypol.html)(http://www.lsbu.ac.uk/water/hypol.html)

Polysaccharides are more hydrophobic if they have a Polysaccharides are more hydrophobic if they have a greater number of internal hydrogen bonds, and as their greater number of internal hydrogen bonds, and as their hydrophobicity increases there is less direct interaction hydrophobicity increases there is less direct interaction with water with water Divided into Divided into homopolysaccharides homopolysaccharides (e.g.Starch, glycogen, (e.g.Starch, glycogen, cellulose, and chitin) & cellulose, and chitin) & heteropolysaccharides heteropolysaccharides (glycoaminoglycans or GAGs, murein).(glycoaminoglycans or GAGs, murein).

4.2. Classification of Polisacharides4.2. Classification of Polisacharides

4.2.1.HOMOPOLYSACCHARIDES4.2.1.HOMOPOLYSACCHARIDES

Found in abundance in natureFound in abundance in natureImportant examples: starch, glycogen, cellulose, Important examples: starch, glycogen, cellulose, and chitinand chitinStarch, glycogen, and cellulose all yield D-Starch, glycogen, and cellulose all yield D-glucose when they are hydrolyzedglucose when they are hydrolyzedCellulose - primary component of plant cellsCellulose - primary component of plant cellsChitin – principal structural component of Chitin – principal structural component of exoskeletons of arthropods and cell walls of exoskeletons of arthropods and cell walls of many fungi; yield glucose derivative N-acetyl many fungi; yield glucose derivative N-acetyl glucosamine when it is hydrolyzed. glucosamine when it is hydrolyzed.

STARCH (Homopolysaccharide)STARCH (Homopolysaccharide)

A naturally abundant nutrient carbohydrate, (CA naturally abundant nutrient carbohydrate, (C66HH1010OO55)n, found )n, found chiefly in the seeds, fruits, tubers, roots, and stem pith of chiefly in the seeds, fruits, tubers, roots, and stem pith of plants, notably in corn, potatoes, wheat, and rice, and varying plants, notably in corn, potatoes, wheat, and rice, and varying widely in appearance according to source but commonly widely in appearance according to source but commonly prepared as a white amorphous tasteless powder. prepared as a white amorphous tasteless powder. Any of various substances, such as natural starch, used to Any of various substances, such as natural starch, used to stiffen cloth, as in laundering. stiffen cloth, as in laundering. Two polysaccharides occur together in starch: amylose and Two polysaccharides occur together in starch: amylose and amylopectinamylopectinAmylose – unbranched chains of D-glucose residues linked Amylose – unbranched chains of D-glucose residues linked with with alfa(alfa(1,4,)glycosidic bonds1,4,)glycosidic bondsAmylopectin – a branched polymer containing both Amylopectin – a branched polymer containing both alfaalfa(1,4,) (1,4,) and alfa(1,6) glcosidic linkages; the and alfa(1,6) glcosidic linkages; the alfa(alfa(1,6) branch points 1,6) branch points may occur every 20-25 glucose residues to prevent helix may occur every 20-25 glucose residues to prevent helix formationformationStarch digestion begins in the mouth; alfa-amylase in the Starch digestion begins in the mouth; alfa-amylase in the saliva initiates hydrolysis of the gycosidic linkagessaliva initiates hydrolysis of the gycosidic linkages

AmyloseAmylose

amylopectinamylopectin

GLYCOGEN (Homopolysaccharide)GLYCOGEN (Homopolysaccharide)Glycogen is the storage form of glucose in animals and humans Glycogen is the storage form of glucose in animals and humans which is analogous to the starch in plants. which is analogous to the starch in plants. Glycogen is synthesized and stored mainly in the liver and the Glycogen is synthesized and stored mainly in the liver and the muscles. muscles. Structurally, glycogen is very similar to amylopectin with alpha Structurally, glycogen is very similar to amylopectin with alpha acetal linkages, however, it has even more branching and more acetal linkages, however, it has even more branching and more glucose units are present than in amylopectin.glucose units are present than in amylopectin. Various samples of glycogen have been measured at 1,700-Various samples of glycogen have been measured at 1,700-600,000 units of glucose.600,000 units of glucose.The structure of glycogen consists of long polymer chains of The structure of glycogen consists of long polymer chains of glucose units connected by an glucose units connected by an alpha acetalalpha acetal linkage. linkage. The branches are formed by linking C # 1 to a C # 6 through an The branches are formed by linking C # 1 to a C # 6 through an acetal linkages. acetal linkages. In glycogen, the branches occur at intervals of 8-10 glucose units, In glycogen, the branches occur at intervals of 8-10 glucose units, while in amylopectin the branches are separated by 12-20 glucose while in amylopectin the branches are separated by 12-20 glucose units.units.

STRUCTURE OF GLYCOGENSTRUCTURE OF GLYCOGEN

CELLULOSE CELLULOSE (Homopolysaccharide)(Homopolysaccharide)

Cellulose is found in plants as microfibrils (2-20 nm diameter and Cellulose is found in plants as microfibrils (2-20 nm diameter and 100 - 40 000 nm long). These form the structurally strong  100 - 40 000 nm long). These form the structurally strong  framework in the cell walls. The microfibrils are held together by framework in the cell walls. The microfibrils are held together by hydrogen bonding and may contain 12,000 glucose units each.hydrogen bonding and may contain 12,000 glucose units each.Cellulose is mostly prepared from wood pulp Cellulose is mostly prepared from wood pulp Cellulose is a linear polymer of β-(1 4)-D-glucopyranose units in Cellulose is a linear polymer of β-(1 4)-D-glucopyranose units in 44CC11 conformation. The fully equatorial conformation of β-linked conformation. The fully equatorial conformation of β-linked glucopyranose residues stabilizes the chair structure, minimizing its glucopyranose residues stabilizes the chair structure, minimizing its flexibilityflexibilityCellulose has many uses as an anticake agent, emulsifier, stabilizer, Cellulose has many uses as an anticake agent, emulsifier, stabilizer, dispersing agent, thickener, and gelling agent but these are dispersing agent, thickener, and gelling agent but these are generally subsidiary to its most important use of holding on to water. generally subsidiary to its most important use of holding on to water. Water cannot penetrate crystalline cellulose but dry amorphous Water cannot penetrate crystalline cellulose but dry amorphous cellulose absorbs water becoming soft and flexible. cellulose absorbs water becoming soft and flexible. Purified cellulose is used as the base material for a number of Purified cellulose is used as the base material for a number of water-soluble derivatives e.g. Methyl cellulose, carbomethycellulosewater-soluble derivatives e.g. Methyl cellulose, carbomethycellulose

The ability to digest cellulose is found only The ability to digest cellulose is found only in microbes that possess enzyme in microbes that possess enzyme cellulase.cellulase.

Certain animal species (termites and Certain animal species (termites and cows) use such organisms in their cows) use such organisms in their digestives tracts to digest cellulose.digestives tracts to digest cellulose.

The breakdown of cellulose makes The breakdown of cellulose makes glucose available to both the microbes and glucose available to both the microbes and their host.their host.

Cellulose also make up the dietary fibre. Cellulose also make up the dietary fibre.

Cellulose as polymer of β-D-glucoseCellulose as polymer of β-D-glucose

Cellulose in 3D Cellulose in 3D

CELLULOSECELLULOSE

CHITIN (Homosaccharide)CHITIN (Homosaccharide)

Chitin is a polymer that can be found in anything from Chitin is a polymer that can be found in anything from the shells of beetles to webs of spiders. It is present all the shells of beetles to webs of spiders. It is present all around us, in plant and animal creatures. around us, in plant and animal creatures. It is sometimes considered to be a spinoff of It is sometimes considered to be a spinoff of cellulosecellulose, , because the two are very molecularly similar. because the two are very molecularly similar. Cellulose contains a hydroxy group, and chitin contains Cellulose contains a hydroxy group, and chitin contains acetamide. acetamide. Chitin is unusual because it is a "natural polymer," or a Chitin is unusual because it is a "natural polymer," or a combination of elements that exists naturally on earth. combination of elements that exists naturally on earth. Usually, polymers are man-made. Crabs, beetles, worms Usually, polymers are man-made. Crabs, beetles, worms and mushrooms contain large amount of chitin. and mushrooms contain large amount of chitin. Chitin is a very firm material, and it help protect an insect Chitin is a very firm material, and it help protect an insect against harm and pressure against harm and pressure

Structure of the chitin molecule, showing two of the N-Structure of the chitin molecule, showing two of the N-acetylglucosamine units that repeat to form long chains in acetylglucosamine units that repeat to form long chains in

beta-1,4 linkage.beta-1,4 linkage.

CHITOSANCHITOSANA spinoff of chitin that has been discovered by the A spinoff of chitin that has been discovered by the market is chitosan. This is a man-made molecule that is market is chitosan. This is a man-made molecule that is often used to dye shirts and jeans in the clothing often used to dye shirts and jeans in the clothing industry. industry. Chitosan can be used within the human body to regulate Chitosan can be used within the human body to regulate diet programs, and researchers are looking into ways in diet programs, and researchers are looking into ways in which it can sure diseases. which it can sure diseases. Chitin, the polysaccharide polymer from which chitosan Chitin, the polysaccharide polymer from which chitosan is derived, is a cellulose-like polymer consisting mainly of is derived, is a cellulose-like polymer consisting mainly of unbranched chains of N-acetyl-D-glucosamine. unbranched chains of N-acetyl-D-glucosamine. Deacetylated chitin, or chitosan, is comprised of chains Deacetylated chitin, or chitosan, is comprised of chains of D-glucosamine. When ingested, chitosan can be of D-glucosamine. When ingested, chitosan can be considered a dietary fiber. considered a dietary fiber.

CHEMICAL STRUCTURE OF CHITOSANCHEMICAL STRUCTURE OF CHITOSANhttp://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/chi_0067.shtmlhttp://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/chi_0067.shtml

4.2.2.HETEROPOLYSACCHARIDES4.2.2.HETEROPOLYSACCHARIDES

Are high-molecular-weight carbohydrate Are high-molecular-weight carbohydrate polymers more than one kind of polymers more than one kind of monosaccharidemonosaccharide

Important examples include Important examples include glycosaminoglycans (GAGs) – the glycosaminoglycans (GAGs) – the principle components of proteoglycans principle components of proteoglycans and murein, a major component of and murein, a major component of bacterial cell walls. bacterial cell walls.

Glycoaaminoglycans (GAGs)Glycoaaminoglycans (GAGs)

GAGs are linear polymers with GAGs are linear polymers with disaccharides repeating units. Many of disaccharides repeating units. Many of their sugar residues are amino derivatives. their sugar residues are amino derivatives.

The repeating units contain hexuronic acid The repeating units contain hexuronic acid (a uronic acid contain 6-C atoms) except (a uronic acid contain 6-C atoms) except for keratan sulphate – contains galactose. for keratan sulphate – contains galactose.

Usually N-acetylglucosamine sulphate is Usually N-acetylglucosamine sulphate is also present except in hyaluronic acid also present except in hyaluronic acid which contain N-acetylglucosamine. which contain N-acetylglucosamine.

Many disacharide units contain both carboxyl Many disacharide units contain both carboxyl nd sulfate functions groups.nd sulfate functions groups.

GAGs are classified according to their sugar GAGs are classified according to their sugar residues, the linkages between residues and residues, the linkages between residues and the presence and location of sulphate groups.the presence and location of sulphate groups.

5 classes has been distinguished: hyaluronic 5 classes has been distinguished: hyaluronic acid, chondroitin sulfate, dermatan sulfate, acid, chondroitin sulfate, dermatan sulfate, heparin and keratan sulfateheparin and keratan sulfate

THE SPECIFIC GAGs OF PHYSIOLOGICAL THE SPECIFIC GAGs OF PHYSIOLOGICAL SIGNIFICANCE SIGNIFICANCE

Hyaluronic acidHyaluronic acid OccurenceOccurence : synovial fluid, ECM of loose : synovial fluid, ECM of loose connective tissueconnective tissueHyaluronic acidHyaluronic acid is unique among the GAGs is unique among the GAGs because it does not contain any sulfate and is because it does not contain any sulfate and is not found covalently attached to proteins. It not found covalently attached to proteins. It forms non-covalently linked complexesforms non-covalently linked complexes with with proteoglycansproteoglycans in the ECM. in the ECM.Hyaluronic acid polymers are very large (100 - Hyaluronic acid polymers are very large (100 - 10,000 kD) and can displace a large volume of 10,000 kD) and can displace a large volume of water. water.

Hyaluronic acidHyaluronic acid (D-glucuronate + GlcNAc) (D-glucuronate + GlcNAc)

Dermatan sulfateDermatan sulfate (L-iduronate + GlcNAc sulfate) (L-iduronate + GlcNAc sulfate)

OccurenceOccurence : skin, blood vessels, heart valves : skin, blood vessels, heart valves

Chondroitin sulfate Chondroitin sulfate (D-glucuronate + (D-glucuronate + GalNAc sulfate)GalNAc sulfate)

OccurenceOccurence : cartilage, bone, heart valves ; : cartilage, bone, heart valves ;It is the most abundant GAG.It is the most abundant GAG.

Heparin and heparan sulfate Heparin and heparan sulfate (D-glucuronate (D-glucuronate sulfate + N-sulfo-D-glucosamine)sulfate + N-sulfo-D-glucosamine)

Heparans have less sulfate groups than heparins Heparans have less sulfate groups than heparins OccurenceOccurence : : Heparin Heparin :component of intracellular granules of mast cells lining the :component of intracellular granules of mast cells lining the arteries of the lungs, liver and skin arteries of the lungs, liver and skin Heparan sulfateHeparan sulfate : basement : basement membranes, component of cell surfacesmembranes, component of cell surfaces

Keratan sulfate Keratan sulfate ( Gal + GlcNAc sulfate)( Gal + GlcNAc sulfate)

OccurenceOccurence : cornea, bone, cartilage ; : cornea, bone, cartilage ;

Keratan sulfates are often aggregated with chondroitin Keratan sulfates are often aggregated with chondroitin sulfatessulfates..

MUREIN (Peptidoglycan)MUREIN (Peptidoglycan)

PeptidoglycanPeptidoglycan, also known as , also known as mureinmurein, is a , is a polymer consisting of consisting of sugars and amino acids that forms a mesh-like layer outside the sugars and amino acids that forms a mesh-like layer outside the plasma membrane of of eubacteria. .

The sugar component consists of alternating residues of β-(1,4) The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid residues. linked N-acetylglucosamine and N-acetylmuramic acid residues.

Attached to the N-acetylmuramic acid is a peptide chain of three to Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. five amino acids.

The peptide chain can be cross-linked to the peptide chain of The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. another strand forming the 3D mesh-like layer.

Some Some Archaea have a similar layer of have a similar layer of pseudopeptidoglycan. .

SUMMARYSUMMARYMonosaccharides, the simplest carbohydrates, are Monosaccharides, the simplest carbohydrates, are classified as aldoses or ketoses.classified as aldoses or ketoses.The cyclic hemiacetal and hemiketal forms of The cyclic hemiacetal and hemiketal forms of monosacchs have either alfa or beta configuration at monosacchs have either alfa or beta configuration at their anomeric carbon.their anomeric carbon.Monosacch derivatives include aldonic acids, uronic Monosacch derivatives include aldonic acids, uronic acids, deoxy sugars, amino sugars, alfa & beta acids, deoxy sugars, amino sugars, alfa & beta glycosides.glycosides.Disaccharides simplest polysaccharides occuring as Disaccharides simplest polysaccharides occuring as hydrolysis products of larger molecules e.g. hydrolysis products of larger molecules e.g. Lactose,sucroseLactose,sucroseOligosaccharides play important roles in determining Oligosaccharides play important roles in determining protein structure and in cell-surface recognition protein structure and in cell-surface recognition phenomena. Oligosacchs with 3 or more sugar residues phenomena. Oligosacchs with 3 or more sugar residues are mostly found in plants.are mostly found in plants.

Summary contd. -1Summary contd. -1POLOYSACCHARIDES consist of monosacchs POLOYSACCHARIDES consist of monosacchs linked by glycosidic bonds.linked by glycosidic bonds.Cellulose and chitin are Cellulose and chitin are structural polysacchsstructural polysacchs with beta(1-4) linkages that adopt rigid and with beta(1-4) linkages that adopt rigid and extended structures.extended structures.The The storage polysacchsstorage polysacchs starch and glycogen starch and glycogen consist of alfa-glycosidically linked glucose consist of alfa-glycosidically linked glucose residuesresiduesGlycosaminoglycans Glycosaminoglycans are unbranched are unbranched polysacchs containing uronic acids and amino polysacchs containing uronic acids and amino sugars that are often sulfatedsugars that are often sulfated

END NOTESEND NOTES

The destiny of a nation depends on the The destiny of a nation depends on the manner in which it feeds itself. manner in which it feeds itself.

We eat to live, NOT, live to eat.We eat to live, NOT, live to eat.

Lower your carbohydrate consumption, but Lower your carbohydrate consumption, but balance it with the right amount of protein balance it with the right amount of protein and fat.and fat.