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LECTURE 6LECTURE 6OligoOligo-- and Polyand Polysaccharidessaccharides

Lactose is a disaccharide found in milk. It is composed of a molecule of D-galactose and a molecule of D-glucose bonded by a β-1-4 glycosidic linkage.

Carbohydrates or saccharides Monosaccharide has just one ring, a disaccharide has two, and a polysaccharide has many

QUESTIONSQUESTIONS1.1. What are the most common disaccharidesWhat are the most common disaccharides2.2. What are the products resulting from the hydrolysis of sucroseWhat are the products resulting from the hydrolysis of sucrose3.3. What is the carbohydrate used for the production of penicillin?What is the carbohydrate used for the production of penicillin?4.4. What is the carbohydrate produced by soybean causing flatulence?What is the carbohydrate produced by soybean causing flatulence?5.5. How many groups are carbohydrates classified as polysaccharides?How many groups are carbohydrates classified as polysaccharides?6.6. What are the components of starch?What are the components of starch?7.7. What is the color of What is the color of amyloseamylose reacting with iodine?reacting with iodine?8.8. What is the difference between starch and cellulose in term of What is the difference between starch and cellulose in term of

each glucose constituent?each glucose constituent?9.9. What is the product resulting from the partial and complete What is the product resulting from the partial and complete

hydrolysis of cellulose produce?hydrolysis of cellulose produce?10.10. How much is cellulose found in wood in generalHow much is cellulose found in wood in general

QUESTIONSQUESTIONS

11.11. What is the cellulose product used for plasticWhat is the cellulose product used for plastic12.12. What is the animal starchWhat is the animal starch13.13. What is the carbohydrate polymer found in the exoskeletons of What is the carbohydrate polymer found in the exoskeletons of

insects and spidersinsects and spiders14.14. What are the products of the reaction of glucose and the enzyme What are the products of the reaction of glucose and the enzyme

transglucosidasetransglucosidase15.15. What carbohydrate is the components of dental plaquesWhat carbohydrate is the components of dental plaques16.16. What is the carbohydrate used for gluesWhat is the carbohydrate used for glues17.17. What is the heteropolysaccharides found in the pulp of fruits What is the heteropolysaccharides found in the pulp of fruits

(citrus, apples)(citrus, apples)18.18. What is the polysaccharide found in the bacterial cell wall What is the polysaccharide found in the bacterial cell wall

providing the strength and rigidity for the organismproviding the strength and rigidity for the organism19.19. What is the polysaccharide produced by garlicWhat is the polysaccharide produced by garlic20.20. What is theWhat is the

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OligosaccharidesOligosaccharides Oligosaccharides are compounds in which monosaccharide Oligosaccharides are compounds in which monosaccharide

units are joined by units are joined by glycosidicglycosidic linkageslinkages. . According to the number of units, they are called According to the number of units, they are called

disaccharides, disaccharides, trisaccharidestrisaccharides, , tetrasaccharidestetrasaccharides, , pentasaccharidespentasaccharides etc. etc.

The borderline with polysaccharides cannot be drawn The borderline with polysaccharides cannot be drawn strictly; however the term 'oligosaccharide' is commonly strictly; however the term 'oligosaccharide' is commonly used to refer to a defined structure as opposed to a used to refer to a defined structure as opposed to a polymer of unspecified length or a homologous mixture. polymer of unspecified length or a homologous mixture. When the linkages are of other types, the compounds are When the linkages are of other types, the compounds are regarded as oligosaccharide analogues.regarded as oligosaccharide analogues.

An extremely important biochemical reaction is the An extremely important biochemical reaction is the condensation of two (or more) condensation of two (or more) monosaccharidesmonosaccharides by the by the elimination of water from an OH group present on each of elimination of water from an OH group present on each of the two sugars. the two sugars.

Most commonly the reaction occurs between the Most commonly the reaction occurs between the OHOHpresent on present on C1 C1 of one monosaccharide and that present on of one monosaccharide and that present on C4C4 of the second to form 1 of the second to form 1 4 GLYCOSIDIC linkage. 4 GLYCOSIDIC linkage.

Because the reaction involves Because the reaction involves C1C1, which can exist in either , which can exist in either aa-- or or bb-- forms, we can obtain either an forms, we can obtain either an aa (1(1 4) or a 4) or a bb(1(1 4) 4) glycosideglycoside

Glycoside links to other carbon atoms are fairly common, Glycoside links to other carbon atoms are fairly common, notably 1notably 1 2 and 12 and 1 66

Oligosaccharides

Most common Oligosaccharides (Most common Oligosaccharides (oligooligo-- "several")"several") disaccharides:disaccharides: Sucrose, lactose, and maltoseSucrose, lactose, and maltose TrisaccharideTrisaccharide:: raffinoseraffinose (glucose, (glucose, galactosegalactose and fructose)and fructose) TetrasaccharideTetrasaccharide:: stachyosestachyose (2 (2 galactosesgalactoses, glucose and fructose), glucose and fructose) PentasaccharidePentasaccharide:: verbascoseverbascose (3 (3 galactosesgalactoses, glucose and , glucose and

fructose)fructose) HexasaccharideHexasaccharide:: ajugoseajugose (4 (4 galactosesgalactoses, glucose and fructose), glucose and fructose) Maltose hydrolyzes to 2 molecules of DMaltose hydrolyzes to 2 molecules of D--glucoseglucose Lactose hydrolyzes to a molecule of glucose and a molecule of Lactose hydrolyzes to a molecule of glucose and a molecule of

galactosegalactose Sucrose hydrolyzes to a Sucrose hydrolyzes to a moledulemoledule of glucose and a molecule of of glucose and a molecule of

fructosefructose

SUCROSE (domestic sugar) is glucose-a (1 → 2) -b-fructose. 1

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Disaccharide Unit 1 Unit 2 Bond Disaccha-ridase

Sucrose glucose fructose α(1→2) sucraseLactose galactose glucose β(1→4) lactaseMaltose glucose glucose α(1→4) maltaseTrehalose glucose glucose α(1→1) trehalaseCellobiose glucose glucose β(1→4) cellobiase

Sucrose (table sugar, cane sugar, saccharose, or beet sugar)Lactose (milk sugar)

Disaccharides are formed by condensing a pair of monosaccharides. The structures of three important disaccharides with the formula C12H22O11 are shown in the figure below

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SucroseSucrose Sucrose, commonly called table sugar, is a Sucrose, commonly called table sugar, is a

disaccharide of glucose (left) and fructose (right)disaccharide of glucose (left) and fructose (right) Hydrolysis yield Hydrolysis yield glucoseglucose and and fructosefructose (invert (invert

sugar) (sucrose: +66.5sugar) (sucrose: +66.5oo ; glucose +52.5; glucose +52.5oo; ; fructose fructose ––9292oo))

IUPAC name β-D-fructofuranosyl-(2→1)-α-D-glucopyranosideOther names sugar, saccharose,Molecular formula C12H22O11

Molar mass 342.30 g/mol

IUPAC = International Union of Pure and Applied Chemistry

Sugar caneSugar beet

systematic name is α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside

LactoseLactose bb--DD--galactosegalactose joined to joined to aa--DD--glucose via glucose via bb (1,4) linkage(1,4) linkage milk contains the milk contains the aa and and bb--anomersanomers in a 2:3 ratioin a 2:3 ratio bb--lactose is sweeter and more soluble than ordinary lactose is sweeter and more soluble than ordinary aa-- lactoselactose used in infant formulations, medium for penicillin production and as used in infant formulations, medium for penicillin production and as

a a diluentdiluent in pharmaceuticalsin pharmaceuticals

MaltoseMaltose 22--glucose molecules joined via glucose molecules joined via aa(1,4) linkage(1,4) linkage known as malt sugarknown as malt sugar produced by the partial hydrolysis of starch (either salivary amylase or produced by the partial hydrolysis of starch (either salivary amylase or

pancreatic amylase)pancreatic amylase) used as a nutrient (malt extract; used as a nutrient (malt extract; HordeumHordeum vulgarevulgare); as a sweetener ); as a sweetener

and as a fermentative reagentand as a fermentative reagentLactuloseLactulose galactosegalactose--bb--(1,4)(1,4)--fructosefructose a semia semi--synthetic disaccharide (not naturally occurring)synthetic disaccharide (not naturally occurring) not absorbed in the GI tractnot absorbed in the GI tract used either as a laxative (used either as a laxative (ChronulacChronulac) or in the management of portal ) or in the management of portal

systemic encephalopathy (systemic encephalopathy (CephulacCephulac)) metabolized in distal ileum and colon by bacteria to lactic acid, metabolized in distal ileum and colon by bacteria to lactic acid,

formic acid and acetic acid (remove ammonia)formic acid and acetic acid (remove ammonia)

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Structures of some oligosaccharidesStructures of some oligosaccharides

An enzymatic product (Beano) can be used to prevent the flatulence

Oligosaccharides occur widely as components of antibiotics derived from various sources

Honey also contains glucose and fructose along withsome volatile oils

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Polysaccharides or Polysaccharides or glycansglycans HomoglycansHomoglycans (starch, cellulose, glycogen, inulin)(starch, cellulose, glycogen, inulin) HeteroglycansHeteroglycans (gums, mucopolysaccharides)(gums, mucopolysaccharides) Characteristics:Characteristics:

Polymers (MW from 200,000)Polymers (MW from 200,000)White and amorphous products (glassy)White and amorphous products (glassy)Not sweetNot sweetNot reducing; do not give the typical aldose or ketose Not reducing; do not give the typical aldose or ketose reactions)reactions)Form colloidal solutions or suspensionsForm colloidal solutions or suspensions

StarchStarch most common storage polysaccharide in plantsmost common storage polysaccharide in plants composed of 10 composed of 10 –– 30% a30% a--amyloseamylose and 70and 70--90% 90%

amylopectinamylopectin depending on the sourcedepending on the source the chains are of varying length, having molecular the chains are of varying length, having molecular

weights from several thousands to half a millionweights from several thousands to half a million

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

suspensions of amylose in water adopt a helical conformation

iodine (I2) can insert inthe middle of the amylose helix to give a blue color that is characteristic anddiagnostic for starch

CelluloseCellulose Polymer of Polymer of bb--DD--glucose attached by glucose attached by bb(1,4) linkages(1,4) linkages Yields glucose upon complete hydrolysisYields glucose upon complete hydrolysis Partial hydrolysis yields cellobiosePartial hydrolysis yields cellobiose Most abundant of all carbohydratesMost abundant of all carbohydrates

Cotton flax: 97Cotton flax: 97--99% cellulose99% cellulose Wood: ~ 50% celluloseWood: ~ 50% cellulose

Gives no color with iodineGives no color with iodine Held together with lignin in woody plant tissuesHeld together with lignin in woody plant tissues

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(in starch)

(in cellulose)

Structure of cellulose

Linear structures of cellulose and chitin(2 most abundant polysaccharides) Products obtained from celluloseProducts obtained from cellulose

Microcrystalline cellulose Microcrystalline cellulose : used as binder: used as binder--disintegrant in disintegrant in tabletstablets

MethylcelluloseMethylcellulose: suspending agent and bulk laxative: suspending agent and bulk laxative Oxidized celluloseOxidized cellulose: hemostat: hemostat Sodium carboxymethyl celluloseSodium carboxymethyl cellulose: laxative: laxative Cellulose acetateCellulose acetate: rayon; photographic film; plastics: rayon; photographic film; plastics Cellulose acetate phthalateCellulose acetate phthalate: enteric coating: enteric coating NitrocelluloseNitrocellulose: explosives; collodion (pyroxylin): explosives; collodion (pyroxylin)

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GlycogenGlycogen also known as animal starchalso known as animal starch stored in muscle and liverstored in muscle and liver present in cells as granules (high MW)present in cells as granules (high MW) contains both a(1,4) links and a(1,6) contains both a(1,4) links and a(1,6)

branches at every 8 to 12 glucose unitbranches at every 8 to 12 glucose unit complete hydrolysis yields glucosecomplete hydrolysis yields glucose glycogen and iodine gives a redglycogen and iodine gives a red--violet colorviolet color hydrolyzed by both a and bhydrolyzed by both a and b--amylases and by amylases and by

glycogen phosphorylaseglycogen phosphorylase

InulinInulin bb--(1,2) linked fructofuranoses(1,2) linked fructofuranoses linear only; no branchinglinear only; no branching lower molecular weight than starchlower molecular weight than starch colors yellow with iodinecolors yellow with iodine hydrolysis yields fructosehydrolysis yields fructose sources include onions, garlic, dandelions and sources include onions, garlic, dandelions and

jerusalem artichokesjerusalem artichokes used as diagnostic agent for the evaluation of used as diagnostic agent for the evaluation of

glomerular filtration rate (renal function test)glomerular filtration rate (renal function test)

Jerusalem artichokes

ChitinChitin

chitin is the second most abundant carbohydrate polymerchitin is the second most abundant carbohydrate polymer present in the cell wall of fungi and in the exoskeletons of present in the cell wall of fungi and in the exoskeletons of

crustaceans, insects and spiderscrustaceans, insects and spiders chitin is used commercially in coatings (extends the shelf chitin is used commercially in coatings (extends the shelf

life of fruits and meats)life of fruits and meats)

DextransDextrans products of the reaction of glucose and the products of the reaction of glucose and the

enzyme transglucosidase from enzyme transglucosidase from Leuconostoc Leuconostoc mesenteroidesmesenteroides

contains a (1,4), a (1,6) and a (1,3) linkagescontains a (1,4), a (1,6) and a (1,3) linkages MW: 40,000; 70,000; 75,000MW: 40,000; 70,000; 75,000 used as plasma extenders (treatment of shock)used as plasma extenders (treatment of shock) also used as molecular sieves to separate also used as molecular sieves to separate

proteins and other large molecules (gel proteins and other large molecules (gel filtration chromatography)filtration chromatography)

components of dental plaquescomponents of dental plaques

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DextrinsDextrins produced by the partial hydrolysis of produced by the partial hydrolysis of

starch along with maltose and glucosestarch along with maltose and glucose dextrins are often referred to as either dextrins are often referred to as either

amylodextrins, erythrodextrins or amylodextrins, erythrodextrins or achrodextrinsachrodextrins

used as mucilages (glues)used as mucilages (glues) also used in infant formulas (prevent the also used in infant formulas (prevent the

curdling of milk in baby’s stomach)curdling of milk in baby’s stomach)

PectinsPectins pectins are pectins are heteropolysaccharideheteropolysaccharides s

found in the found in the pulp of fruits pulp of fruits (citrus, apples)(citrus, apples) on hydrolysis pectins yield galacturonic on hydrolysis pectins yield galacturonic

acid, galactose, arabinose, methanol acid, galactose, arabinose, methanol and acetic acidand acetic acid

pectins are composed of pectins are composed of galactansgalactans and and arabansarabans

used as gelling agents (to make jellies)used as gelling agents (to make jellies)

RESINRESIN The resin produced by most plants is The resin produced by most plants is

composed mainly of volatile fluid composed mainly of volatile fluid terpenesterpenes

Terpenes, (CTerpenes, (C55HH88))nn, are derived , are derived biosynthetically from units of biosynthetically from units of isopreneisoprene(C(C55HH88))

Resin of a pineDimethylallyl pyrophosphate Isopentenyl pyrophosphate

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Bacterial cell wallBacterial cell wall provide strength and rigidity for the provide strength and rigidity for the

organismorganism consists of a polypeptideconsists of a polypeptide--

polysaccharide known as polysaccharide known as petidoglycanpetidoglycanor or mureinmurein

determines the Gram staining determines the Gram staining characteristic of the bacteriacharacteristic of the bacteria

Structure of peptidoglycan

Cell wall of Gram-positive bacteria

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Gram-negative bacteria

Fructose can form either:• a six-member pyranose ring, by reaction of

the C2 keto group with the hydroxyl on C6 • a 5-member furanose ring, by reaction of the

C2 keto group with the hydroxyl on C5.

The representations of the cyclic sugars at right are called Haworth projections

Haworth projections represent the cyclic sugars as having essentially planar rings, with the OH at the anomeric C1 extending either:• below the ring (a) • above the ring (b).