Chem 150 Unit 9 - Biological Molecules II Carbohydrates Carbohydrates play many important roles in biological systems. They represent the major form of

Chem 150Chem 150Unit 9 - Unit 9 - BiologicalBiological Molecules II Molecules II

CarbohydratesCarbohydrates

Carbohydrates play many important roles in biological Carbohydrates play many important roles in biological systems. They represent the major form of chemical systems. They represent the major form of chemical energy for both plants and animals. In plants they energy for both plants and animals. In plants they represent the end product of photosynthesis, and represent the end product of photosynthesis, and therefore connect all living systems to the sun’s therefore connect all living systems to the sun’s

sustaining light energy. Our discussion of sustaining light energy. Our discussion of carbohydrates will also introduce us to biopolymers, of carbohydrates will also introduce us to biopolymers, of which proteins and nucleic acids also belong. One of which proteins and nucleic acids also belong. One of

these polymers, the structural polysaccharide these polymers, the structural polysaccharide cellulose, ties more of the earth’s organic carbon than cellulose, ties more of the earth’s organic carbon than

any other molecule.any other molecule.

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IntroductionIntroduction

PolymersPolymers are large molecules that are made by stringing are large molecules that are made by stringing together, like beads on a string, smaller units called together, like beads on a string, smaller units called monomersmonomers..• Poly- is the Greek prefix meaning “Poly- is the Greek prefix meaning “many”.many”.The names of may polymers describe what they are made fromThe names of may polymers describe what they are made from• Polyethylene is made by stringing together many ethylene Polyethylene is made by stringing together many ethylene

units.units.• Ethylene (ethene) is the monomerEthylene (ethene) is the monomer

• Polypropylene is made by stringing together many propylene Polypropylene is made by stringing together many propylene units.units.• Propylene (propene) is the monomer.Propylene (propene) is the monomer.

• Polysaccharides are made by stringing together many Polysaccharides are made by stringing together many monosaccharides.monosaccharides.• Monosaccharides (simple sugars) are the monomersMonosaccharides (simple sugars) are the monomers..

33

IntroductionIntroduction

Carbohydrates are placed in to one of three catagories, Carbohydrates are placed in to one of three catagories, depending on the number of monosaccharide units, or depending on the number of monosaccharide units, or residuesresidues, they contain., they contain.

• MonosaccharidesMonosaccharides, contain a single monosaccharide , contain a single monosaccharide residue.residue.

• OligosaccharidesOligosaccharides, contain 2 to 10 monosaccharide , contain 2 to 10 monosaccharide residues.residues.• These include the disaccharides, which contain 2 monosaccharide These include the disaccharides, which contain 2 monosaccharide

residues.residues.

• PolysaccharidesPolysaccharides, which contain more than 10 , which contain more than 10 monosaccharide residues.monosaccharide residues.• These can contain thousands of monosaccharide residues.These can contain thousands of monosaccharide residues.

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MonosaccharidesMonosaccharides

• Monosaccharides are Monosaccharides are polyhydroxy aldehydespolyhydroxy aldehydes or or ketonesketones..

• Monosaccharides contain 3 to 7 carbon atoms.Monosaccharides contain 3 to 7 carbon atoms.

55


Monosaccharides are Monosaccharides are classified according to classified according to the number of carbons the number of carbons and whether they and whether they contain an aldehyde or contain an aldehyde or ketone.ketone.

• The “The “-ose-ose” ending is ” ending is used to designate used to designate carbohydrates.carbohydrates.

66


The physical properties of The physical properties of monosaccharides are heavily monosaccharides are heavily influenced by the large number of influenced by the large number of hydroxy groups that they contain. hydroxy groups that they contain. • There ability to participate in There ability to participate in

numerous hydrogen bonds gives numerous hydrogen bonds gives them high melting points and them high melting points and high solubilities in water.high solubilities in water.• Each hydroxyl group has two Each hydroxyl group has two

hydrogen bonding acceptor sites hydrogen bonding acceptor sites and one hydogen bonding donor and one hydogen bonding donor site.site.

• Each carbonyl group has two Each carbonyl group has two acceptor sites.acceptor sites.

C

C

O H

O

H

H

H

O H

H O

H

H

OH

H

O H

H

O H

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Monosaccharides contain Monosaccharides contain chiral carbonchiral carbon atoms. atoms.• This is what accounts for the large number of different This is what accounts for the large number of different

monosacchides.monosacchides.• For each chiral carbon, For each chiral carbon, nn, a monosacharide has 2, a monosacharide has 2nn

stereoisomers.stereoisomers.• These will be divided among 2These will be divided among 2nn/2 pairs of /2 pairs of enantiomersenantiomers..

•Glucose contains 4 chiral carbonsGlucose contains 4 chiral carbons

•Glucose has 2Glucose has 244 = 16 stereoisomers = 16 stereoisomers

•These stereoisomers can be These stereoisomers can be grouped into 16/2 = 8 pairs of grouped into 16/2 = 8 pairs of enantiomers.enantiomers.

•Glucose contains 4 chiral carbonsGlucose contains 4 chiral carbons

•Glucose has 2Glucose has 244 = 16 stereoisomers = 16 stereoisomers

•These stereoisomers can be These stereoisomers can be grouped into 16/2 = 8 pairs of grouped into 16/2 = 8 pairs of enantiomers.enantiomers.

OC

H

C

C

C

C

C

H

H

HO

H

H

H OH

OH

OH

OH

OH

D-glucose

http://www.preparatorychemistry.com/Bishop_Jmol_carbohydrates.htm







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Fischer projectionsFischer projections are are used to distinguish the used to distinguish the different stereoisomers.different stereoisomers.• The letters The letters DD and and LL are are

used to distinguish used to distinguish between the members between the members of a pair of of a pair of enantiomers.enantiomers.• The D or L designation is The D or L designation is

based on the chiral based on the chiral carbon furthest from the carbon furthest from the carbonyl carbon.carbonyl carbon.

Fischer projection:Fischer projection:Fischer projection:Fischer projection:

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DiasteriomersDiasteriomers are stereoisomers that are not enantiomers. are stereoisomers that are not enantiomers.• Diasteriomers have have different namesDiasteriomers have have different names• Enatiomers have the same name and are distinguished by Enatiomers have the same name and are distinguished by

a a DD or or LL..

enantiomersenantiomersenantiomersenantiomers

diastereomersdiastereomersdiastereomersdiastereomers

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Important monosaccharides.Important monosaccharides.• pentose and hexoses are the most abundantpentose and hexoses are the most abundantPentosesPentoses• D-riboseD-ribose and and D-2-deoxyriboseD-2-deoxyribose are found in DNA, RNA are found in DNA, RNA

and nucleotides such as FADHand nucleotides such as FADH22 and NADH and NADH

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Important monosaccharides.Important monosaccharides.• pentose and hexoses are the most pentose and hexoses are the most

abundantabundantHexosesHexoses• D-glucoseD-glucose (dextrose or blood surgar) - (dextrose or blood surgar) -

major metabolite and strorage form of major metabolite and strorage form of chemical energy.chemical energy.

• D-galactoseD-galactose - combines with glucose - combines with glucose to produce lactose (milk sugar)to produce lactose (milk sugar)

• D-fructoseD-fructose (fruit sugar) - major (fruit sugar) - major metabolite and sweetest tasting natural metabolite and sweetest tasting natural sugar.sugar.• fructose is a fructose is a ketoseketose

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Monosaccharide derivativesMonosaccharide derivatives• Deoxy sugarsDeoxy sugars..

• One or more -OH’s are replaced with -H’sOne or more -OH’s are replaced with -H’s

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Monosaccharide derivativesMonosaccharide derivatives• Amino sugarsAmino sugars..

• One or more -OH’s are replaced with -NHOne or more -OH’s are replaced with -NH22’s’s• Often these are acetylated to form amides.Often these are acetylated to form amides.

Arthritis relief??Arthritis relief??

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Monosaccharide derivativesMonosaccharide derivatives• Alcohol sugarsAlcohol sugars..

• The ketone or aldehyde is reduced to an alcohol are reduced to The ketone or aldehyde is reduced to an alcohol are reduced to

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Monosaccharide derivativesMonosaccharide derivatives• Carboxylic acid sugarsCarboxylic acid sugars..

• The ketone, aldehyde, or primary alcohol is oxidized to a carboxylic The ketone, aldehyde, or primary alcohol is oxidized to a carboxylic acid.acid.

1616

QuestionQuestion

The monosaccharide D-xylose is The monosaccharide D-xylose is shown below. Draw the derivative shown below. Draw the derivative described:described:

A)A) D-2-deoxyxyloseD-2-deoxyxylose

B)B) xylitolxylitol

C)C) D-xylonic acids (carbon 1 is D-xylonic acids (carbon 1 is oxidized to a carboxylic acid)oxidized to a carboxylic acid)

OC

H

C

C

C

CH2

H

HO

H

OH

OH

H

OH

D-xylose

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Carbo Reactions in Foods!!Carbo Reactions in Foods!!

Amino acids + (some) carbohydrates= Browning flavor-Amino acids + (some) carbohydrates= Browning flavor-

The Maillard reaction. Also occurs in you!The Maillard reaction. Also occurs in you!

http://www.food-info.net/uk/colour/maillard.htmhttp://www.food-info.net/uk/colour/maillard.htm

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml

%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5091200.PN.&OS=PN/

5091200&RS=PN/5091200

Try a little corn syrup, honey, baking soda Try a little corn syrup, honey, baking soda to enhance browning!to enhance browning!

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Carbo Reactions in Foods!!Carbo Reactions in Foods!!

But beware acrylamide in fries??!!But beware acrylamide in fries??!!

‘‘

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Reactions of MonosaccharidesReactions of Monosaccharides

Reduction of the carbonylReduction of the carbonyl• In the lab this can be done with HIn the lab this can be done with H22 and a platinum catalyst. and a platinum catalyst.• In the cell, NADH + HIn the cell, NADH + H++ is used. is used.

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Reduction of Aldehydes and Ketones (Unit 8)Reduction of Aldehydes and Ketones (Unit 8)

The same reaction can also be used to reduce aldehydes The same reaction can also be used to reduce aldehydes and ketones to alcohols:and ketones to alcohols:

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Reduction of Aldehydes and Ketones (Unit 8)Reduction of Aldehydes and Ketones (Unit 8)

In biochemistry, NADH + HIn biochemistry, NADH + H++ is used instead of H is used instead of H22

• The reduction of a ketone containing steroid by the enzyme The reduction of a ketone containing steroid by the enzyme Hydroxsteroid dehydrogenaseHydroxsteroid dehydrogenase..

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Oxidation of sugarsOxidation of sugars• Oxidation with CuOxidation with Cu++ The Benedict’s test The Benedict’s test• Sugars that are capable of producing a positve Benedicts Sugars that are capable of producing a positve Benedicts

test are called test are called reducing sugarsreducing sugars..

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Oxidation of Aldehydes (Unit 8)Oxidation of Aldehydes (Unit 8)

Aldehydes can also be oxidized with the copper(II) ion (CuAldehydes can also be oxidized with the copper(II) ion (Cu2+2+))• This reaction oxidizes aldehydes, but not alcohols.This reaction oxidizes aldehydes, but not alcohols.

• The CuThe Cu2+2+ ion forms a clear blue solution ion forms a clear blue solution• The CuThe Cu++ that is produced in the reaction forms an orange/red that is produced in the reaction forms an orange/red

precipitate.precipitate.

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Oxidation of Aldehydes (Unit 8)Oxidation of Aldehydes (Unit 8)

Aldehydes can also be Aldehydes can also be oxidized with the copper(II) oxidized with the copper(II) ion (Cuion (Cu2+2+))• The reaction is called the The reaction is called the

Benedict’s reaction, and Benedict’s reaction, and has been used for years has been used for years in a clinical setting to test in a clinical setting to test for the presence of for the presence of glucose in the urine.glucose in the urine.

C

O H

C

C

C

C

CH2 OH

H

H

HO

H OH

H

OH

OH

glucose

CuCu2+2+CuCu2+2+ CuCu++CuCu++CuCu2+2+ + + CuCu++

CuCu2+2+ + + CuCu++

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Oxidation of sugarsOxidation of sugars• Even though ketones should not give a positive Benedict’s Even though ketones should not give a positive Benedict’s

test, ketoses do.test, ketoses do.• This is because under the basic conditions of the test, the This is because under the basic conditions of the test, the

ketoses can isomerize to form aldoses, which the react.ketoses can isomerize to form aldoses, which the react.

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Reactions with alcohols to form hemiacetals and hemiketalsReactions with alcohols to form hemiacetals and hemiketals• Since monosaccharides contain both hydroxyl groups Since monosaccharides contain both hydroxyl groups

along with either aldehyde or ketone groups, they can react along with either aldehyde or ketone groups, they can react to form hemiacetals and hemiketals.to form hemiacetals and hemiketals.

2727

Reactions of Alcohols with Aldehydes and Ketones (Unit 7)


The first reaction, which is similar to the reduction of The first reaction, which is similar to the reduction of aldehydes and ketones, involves adding an alcohol across aldehydes and ketones, involves adding an alcohol across the carbonyl to form a hemiacetal (from aldehydes) or a the carbonyl to form a hemiacetal (from aldehydes) or a hemiketal (from ketones).hemiketal (from ketones).

CH2H3C

Propanal(Aldehyde)

C

O

H

O CH2 CH3

H

+

Ethanol(Alcohol)

CH2H3C C

O

H

O CH2 CH3

H

(Hemiacetal)

CH3

Propanone(Ketone)

C

O

CH3

O CH2 CH3

H

+

Ethanol(Alcohol)

CH3 C

O

CH3

O CH2 CH3

H

(Hemiketal)

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Hemiacetal and hemiketal formation is catalyzed by acids.Hemiacetal and hemiketal formation is catalyzed by acids.

2929



As we will see with the carbohydrates, the carbonyl group As we will see with the carbohydrates, the carbonyl group and the alchohol that react can come from the same and the alchohol that react can come from the same molecule.molecule.• This will produce a ring molecule.This will produce a ring molecule.

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Cyclic Form of MonosaccharidesCyclic Form of Monosaccharides

Monosaccharides form rings by reacting one of the hydroxyls Monosaccharides form rings by reacting one of the hydroxyls with the carbonyl to form a hemiacetal or hemiketal:with the carbonyl to form a hemiacetal or hemiketal:


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Usually these are drawn using a Usually these are drawn using a Haworth projectHaworth project::

• The OH’s that were on the The OH’s that were on the rightright in the Fisher projection are in the Fisher projection are placed in the placed in the downdown position on the Haworth projection position on the Haworth projection

• The OH’s that were on the The OH’s that were on the leftleft in the Fisher projection are in the Fisher projection are placed in the placed in the upup position on the Haworth projection position on the Haworth projection

• The CHThe CH22OH on the number 5 carbon points up for D sugars OH on the number 5 carbon points up for D sugars and down for L sugars. and down for L sugars.

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The hemiacetal or hemiketal carbon that forms in the ring is The hemiacetal or hemiketal carbon that forms in the ring is called the called the anomericanomeric carbon. carbon.• The anomeric carbon is also chiral, which increases the The anomeric carbon is also chiral, which increases the

number of chiral carbons by 1 and increases the doubles number of chiral carbons by 1 and increases the doubles the number of stereoisomers.the number of stereoisomers.

• The two forms of the anomeric carbon are designated as α The two forms of the anomeric carbon are designated as α or β.or β.• The β-anomer has the -OH pointing up in the ring form.The β-anomer has the -OH pointing up in the ring form.• The α-anomer has the -OH pointing down in the ring form.The α-anomer has the -OH pointing down in the ring form.

3333


The ring formation is a dynamic equilibrium reaction.The ring formation is a dynamic equilibrium reaction.• The open form can switch back and forth between the two The open form can switch back and forth between the two

ring forms.ring forms.

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When naming the ring forms of monosaccharides, the When naming the ring forms of monosaccharides, the endings -endings -pyranosepyranose and - and -furanosefuranose to designate the six- to designate the six-member and five-member rings, respectively.member and five-member rings, respectively.

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In general, the -OH on the chiral carbon furthest from the the In general, the -OH on the chiral carbon furthest from the the carbonyl is the one that reacts to from the pyranose or carbonyl is the one that reacts to from the pyranose or furanose ring. This means thatfuranose ring. This means that• Aldohexoses will form pyranose rings:Aldohexoses will form pyranose rings:

• Aldopentoses and ketohexoses will form furanose rings:Aldopentoses and ketohexoses will form furanose rings:

DD-glucose-glucose(aldohexose)(aldohexose)

DD-glucose-glucose(aldohexose)(aldohexose)

DD-ribose-ribose(aldopentose)(aldopentose)

DD-ribose-ribose(aldopentose)(aldopentose)

DD-fructose-fructose(ketohexose)(ketohexose)

DD-fructose-fructose(ketohexose)(ketohexose)

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Question (Clicker)Question (Clicker)

Shown below is the Fischer Shown below is the Fischer projection for sorboseprojection for sorbose

Is the structure shownIs the structure shownA)A) D-sorboseD-sorbose

B)B) L-sorboseL-sorbose

Draw and name the α and β Draw and name the α and β ring forms for sorbosering forms for sorbose

CH2

C

OH

O

C

C

C

CH2 OH

H

HO

H OH

H

OH

OH

CH3OH

H

CH2OH

H OH

OH HO

α-α-DD-sorbofuranose-sorbofuranoseα-α-DD-sorbofuranose-sorbofuranose

CH2OH

OH

H

CH2OH

H OH

OH HO

β-β-DD-sorbofuranose-sorbofuranoseβ-β-DD-sorbofuranose-sorbofuranose

3737

Question (Clicker)Question (Clicker)

Shown to the below is the Shown to the below is the Fischer projection for galactoseFischer projection for galactose

Is the structure shownIs the structure shownA)A) DD-galactose-galactose

B)B) LL-galactose-galactose

Draw and name the α and β ring Draw and name the α and β ring forms for sorboseforms for sorbose

C

C

C

C

C

CH2

O H

HO

H

H

HO

OH

H

OH

OH

H

β-β-LL-galactopyranose-galactopyranoseβ-β-LL-galactopyranose-galactopyranose

OH

OH

OH

H

OH

HOH

H

H

CH2OH

α-α-LL-galactopyranose-galactopyranoseα-α-LL-galactopyranose-galactopyranose

OH

OH

H

OH

OH

HOH

H

H

CH2OH

3838

OligosaccharidesOligosaccharides

Monosaccharides are connected to one another to form Monosaccharides are connected to one another to form oligosaccharides and polysaccharides by reacting the oligosaccharides and polysaccharides by reacting the anomeric (hemiacetal or hemiketal) hydroxyl group on one anomeric (hemiacetal or hemiketal) hydroxyl group on one sugar in its ring form, with a hydroxyl group from another sugar in its ring form, with a hydroxyl group from another sugar.sugar.• We saw in Unit 8 how this leads to the formation of acetals We saw in Unit 8 how this leads to the formation of acetals

and ketals.and ketals.• The bond that forms between the two monosaccharides is The bond that forms between the two monosaccharides is

called a called a glycosidic bondglycosidic bond. .

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A hemiacetal or hemiketal can react with a second alcohol to A hemiacetal or hemiketal can react with a second alcohol to form an acetal or ketal.form an acetal or ketal.• This is a substitution reaction and produces an water This is a substitution reaction and produces an water

molecule:molecule:O CH2 CH3H

Ethanol(Alcohol)

CH2H3C C

O

H

O CH2 CH3

H

(Hemiacetal)

+

Ethanol(Alcohol)

CH3 C

O

CH3

O CH2 CH3

H

(Hemiketal)

+

O CH2 CH3H

CH2 CH3

CH2H3C C

O

H

O CH2 CH3 + H O H

CH2 CH3

CH3 C

O

O CH2 CH3 + H O H

CH3

(Acetal)

(Ketal)

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The The disaccharidedisaccharide DD-maltose-maltose forms when the anomeric forms when the anomeric carbon on a carbon on a DD-glucopyranose molecule in the α form reacts -glucopyranose molecule in the α form reacts with the hydroxyl group on the forth carbon of a second with the hydroxyl group on the forth carbon of a second DD--glucopyranose molecule:glucopyranose molecule:• The bond that forms is called an α(1→4) glycosidic bondThe bond that forms is called an α(1→4) glycosidic bond

Maltose is produced Maltose is produced from the breakdown from the breakdown of the of the polysaccharides polysaccharides starch and glycogenstarch and glycogen

Maltose is produced Maltose is produced from the breakdown from the breakdown of the of the polysaccharides polysaccharides starch and glycogenstarch and glycogen

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Maltose is still able to Maltose is still able to reduce Cureduce Cu++ in a in a Benedict’s test, though it Benedict’s test, though it is only 1/2 as reactive.is only 1/2 as reactive.• Like monosaccharides, Like monosaccharides,

maltose is considered a maltose is considered a reducing sugarreducing sugar..

• This is because the one This is because the one monosaccharide is still monosaccharide is still able to open to expose able to open to expose an aldehyde.an aldehyde.

nonreducing endnonreducing endnonreducing endnonreducing end reducing endreducing endreducing endreducing end

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The The disaccharidedisaccharide DD-cellobiose-cellobiose forms when the anomeric forms when the anomeric carbon on a carbon on a DD-glucopyranose molecule in the β form reacts -glucopyranose molecule in the β form reacts with the hydroxyl group on the forth carbon of a second with the hydroxyl group on the forth carbon of a second DD--glucopyranose molecule:glucopyranose molecule:• The bond that forms is called an β(1→4) glycosidic bondThe bond that forms is called an β(1→4) glycosidic bond

Cellobiose is Cellobiose is produced from the produced from the breakdown of the breakdown of the polysaccharids polysaccharids cellulose.cellulose.

Unlike the α(1→4) Unlike the α(1→4) glycosidic bond in glycosidic bond in maltose, most maltose, most organisms are organisms are unable to cleave the unable to cleave the β(1→4) glycosidic β(1→4) glycosidic bondbond

Cellobiose is Cellobiose is produced from the produced from the breakdown of the breakdown of the polysaccharids polysaccharids cellulose.cellulose.

Unlike the α(1→4) Unlike the α(1→4) glycosidic bond in glycosidic bond in maltose, most maltose, most organisms are organisms are unable to cleave the unable to cleave the β(1→4) glycosidic β(1→4) glycosidic bondbond

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The The disaccharidedisaccharide DD-lactose-lactose forms when the anomeric forms when the anomeric carbon on a carbon on a DD-galactopyranose molecule in the β form reacts -galactopyranose molecule in the β form reacts with the hydroxyl group on the forth carbon of a with the hydroxyl group on the forth carbon of a DD--glucopyranose molecule:glucopyranose molecule:• The bond that forms is called an β(1→4) glycosidic bondThe bond that forms is called an β(1→4) glycosidic bond

Lactose is milk Lactose is milk sugar.sugar.

By the age of 5, By the age of 5, some people some people become unable to become unable to break the β(1→4) break the β(1→4) glycosidic bond in glycosidic bond in lactose, resulting in lactose, resulting in lactose intolerance.lactose intolerance.

Lactose is milk Lactose is milk sugar.sugar.

By the age of 5, By the age of 5, some people some people become unable to become unable to break the β(1→4) break the β(1→4) glycosidic bond in glycosidic bond in lactose, resulting in lactose, resulting in lactose intolerance.lactose intolerance.

4444


The The disaccharidedisaccharide DD-sucrose-sucrose forms when the anomeric forms when the anomeric carbon on a carbon on a DD-glucopyranose molecule in the α form reacts -glucopyranose molecule in the α form reacts with the hydroxyl group of the anomeric carbon of with the hydroxyl group of the anomeric carbon of DD--fructofuranose in the β form:fructofuranose in the β form:• The bond that forms is called an α,β(1The bond that forms is called an α,β(1↔↔2) glycosidic bond2) glycosidic bond

Sucrose is table Sucrose is table sugar.sugar.

Because both Because both anomeric carbons anomeric carbons are involved in are involved in forming the forming the glycosidic bond, glycosidic bond, sucrose is not a sucrose is not a reducing sugarreducing sugar..

Sucrose is table Sucrose is table sugar.sugar.

Because both Because both anomeric carbons anomeric carbons are involved in are involved in forming the forming the glycosidic bond, glycosidic bond, sucrose is not a sucrose is not a reducing sugarreducing sugar..

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There are also oligosaccharides with 3 or more There are also oligosaccharides with 3 or more monosaccharidesmonosaccharides• The blood group antigens are oligosaccharides that are The blood group antigens are oligosaccharides that are

attached to lipids and proteins found on cell surfaces.attached to lipids and proteins found on cell surfaces.

A: N-Acetyl-A: N-Acetyl-DD-galactosamine-galactosamine(as shown)(as shown)B: B: DD-galactose-galactoseO: noneO: none

A: N-Acetyl-A: N-Acetyl-DD-galactosamine-galactosamine(as shown)(as shown)B: B: DD-galactose-galactoseO: noneO: none

4646

PolysaccharidesPolysaccharides

Polysaccharides are polymers of 10 or more monosaccharide Polysaccharides are polymers of 10 or more monosaccharide unitsunits• HomopolysaccharidesHomopolysaccharides contain a single type of contain a single type of

monosaccharide unit.monosaccharide unit.• HeteropolysaccharidesHeteropolysaccharides contain more than one typee of contain more than one typee of

monosaccharide unit.monosaccharide unit.

4747


The The polysaccharide cellulose polysaccharide cellulose is a structural polymer is a structural polymer produced by plants:produced by plants:• It is a linear, unbranched polyer, with D-glucopyranose It is a linear, unbranched polyer, with D-glucopyranose

units connected by β(1→4) glycosidic bondsunits connected by β(1→4) glycosidic bonds

4848


The The polysaccharide cellulose polysaccharide cellulose is a structural polymer is a structural polymer produced by plants:produced by plants:• Cellulose forms a very insoluble, fibrous networkCellulose forms a very insoluble, fibrous network• Most organism are unable to digest cellulose because they Most organism are unable to digest cellulose because they

lac the enzymes needed to break the β(1→4) glycosidic lac the enzymes needed to break the β(1→4) glycosidic bondsbonds

4949


The The polysaccharide starch polysaccharide starch is a polymer produced by plants is a polymer produced by plants for glucose storage:for glucose storage:• It is a linear, or branched polymer, with It is a linear, or branched polymer, with DD-glucopyranose units -glucopyranose units

connected by α(1→4) glycosidic bondsconnected by α(1→4) glycosidic bonds

amyloseamyloseamyloseamylose

amylopectinamylopectinamylopectinamylopectin

5050


The The polysaccharide starch polysaccharide starch is a polymer produced by plants is a polymer produced by plants for glucose storage:for glucose storage:• Unlike cellulose, starch has a very open and soluble Unlike cellulose, starch has a very open and soluble

structure.structure.• Animals also produce a storage form of glucose called Animals also produce a storage form of glucose called

glycogenglycogen, which has a structure similar to amylopectin., which has a structure similar to amylopectin.

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HeteropolymersHeteropolymers• Hyaluronic acidHyaluronic acid

• Found in lubricating fluid that surrounds joints and in the vitreous Found in lubricating fluid that surrounds joints and in the vitreous humor of the eye.humor of the eye.

5252


HeteropolymersHeteropolymers• Chondroitin SulfateChondroitin Sulfate

• Present in connective tissuePresent in connective tissue

The EndThe End

Documents

Chem 150 Unit 9 - Biological Molecules II Carbohydrates Carbohydrates play many important roles in biological systems. They represent the major form of