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AnnouncementsAnnouncements & Agenda& Agenda (04/09/07)(04/09/07)Extra Credit Assignment Due NOW!Extra Credit Assignment Due NOW!Pick Up Graded QuizzesPick Up Graded QuizzesQuiz Friday (13.4, 13.5, & Ch 14)Quiz Friday (13.4, 13.5, & Ch 14)

TodayToday More on Carbohydrates (14.1-14.3)More on Carbohydrates (14.1-14.3)

MonosaccharidesMonosaccharides Cyclic MonosaccharidesCyclic Monosaccharides

Reactions of carbohydratesReactions of carbohydrates DisaccharidesDisaccharides

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acid hydrolysisacid hydrolysis OO

|||| OO CH CH33——CC——OH + NHOH + NH44

++ClCl–– |||| HClHCl + H+ H22O O

CHCH33——CC—NH—NH22

NaOHNaOH OO ||||

CHCH33——CC——OO– – NaNa++ + NH + NH33

base hydrolysisbase hydrolysis

Last Time: AmiLast Time: Amidde e HydrolysisHydrolysis

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Last Time: Carbohydrates IntroLast Time: Carbohydrates Intro

• a major source of a major source of energy from our diet energy from our diet

• composed of C, H, & Ocomposed of C, H, & O• also known as also known as

saccharides, which saccharides, which means “sugars.”means “sugars.”

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Last Time: Types of CarbohydratesLast Time: Types of Carbohydrates

• Monosaccharides:Monosaccharides: simplest carbohydrates. simplest carbohydrates. • Disaccharides:Disaccharides: consist of two monosaccharides. consist of two monosaccharides.• Polysaccharides:Polysaccharides: contain many monosaccharides. contain many monosaccharides.

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Last Time: MonosaccharidesLast Time: Monosaccharides

• typically 3-6 carbon atomstypically 3-6 carbon atoms• have a C=O group (aldehyde or ketone)have a C=O group (aldehyde or ketone)

• aldosesaldoses• ketosesketoses

• several hydroxyl groupsseveral hydroxyl groups

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AldosesAldoses

• monosaccharides with an monosaccharides with an aldehyde group… aldehyde group…

• ……and many hydroxyl and many hydroxyl groups.groups.

triose triose (3C atoms)(3C atoms)tetrose tetrose (4C atoms)(4C atoms)pentosepentose (5C atoms) (5C atoms)hexose hexose (6C atoms)(6C atoms)

OO ║║

CC─H aldose─H aldose ││ HH── C C─OH─OH │ │ HH── C C─OH─OH │ │

CHCH22OHOH

ErythoseErythose

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KetosesKetoses

• monosaccharides with a monosaccharides with a ketone group…ketone group…

• ……and many hydroxyl and many hydroxyl groups.groups.

CCHH22OH OH │ │ C=C=O ketoseO ketose │ │ HH── C C─OH─OH ││ HH── C C─OH─OH │ │

HH──CC─OH─OH ││ CHCH22OHOH

Fructose, a ketohexose

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Fischer ProjectionsFischer Projections• also used to represent carbohydrates.also used to represent carbohydrates.• places the most oxidized group at the top.places the most oxidized group at the top.• shows chiral carbons as the intersection of shows chiral carbons as the intersection of

vertical and horizontal lines.vertical and horizontal lines.

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D & L Notations: Know This Now…D & L Notations: Know This Now…In a Fischer projection, the In a Fischer projection, the −OH group on the−OH group on the• chiral carbon chiral carbon farthest from the carbonyl groupfarthest from the carbonyl group determines determines

an L or D isomer. an L or D isomer. • left = left = LL for the L-formfor the L-form..• right = right = DD for the D-formfor the D-form. (MOST COMMON IN NATURE!). (MOST COMMON IN NATURE!)

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Learning CheckLearning Check

Identify each as the D or L isomer.Identify each as the D or L isomer. A.A. B.B. C. C.

__-Ribose __-Ribose __- Threose __- Fructose __- Threose __- Fructose

CH2OH

HO H

HO H

HHO

O

C H

CH2OH

HO H

OHH

O

C H

CH2OH

H OH

H OH

HO H

O

CH2OH

L L D

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D-GlucoseD-Glucose

• found in fruits, corn found in fruits, corn syrup, and honeysyrup, and honey

• an an aldoaldohexose with hexose with the formula Cthe formula C66HH1212OO66

• known as known as blood blood sugarsugar in the body in the body

• the monosaccharide the monosaccharide in polymers of in polymers of starch, cellulose, starch, cellulose, and glycogenand glycogen

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Blood Glucose LevelBlood Glucose LevelIn the body, In the body, • normal blood: [glucose] = 70-90 mg/dL.normal blood: [glucose] = 70-90 mg/dL.• a glucose tolerance test measures blood a glucose tolerance test measures blood

glucose for several hours after ingesting glucose for several hours after ingesting glucose.glucose.

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D-FructoseD-Fructose

• is a is a ketoketohexose hexose CC66HH1212OO66

• is the is the sweetest sweetest carbohydratecarbohydrate

• found in fruit juices found in fruit juices and honeyand honey

• converts to glucose converts to glucose in the bodyin the body

H OH

CH2OH

C

HO

H OH

H

C

O

C

C

CH2OH

D-Fructose

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D-GalactoseD-Galactose

• is an is an aldoaldohexose hexose CC66HH1212OO66..

• notnot found free in nature. found free in nature.• is obtained from lactose, is obtained from lactose,

a disaccharide.a disaccharide.• has a similar structure to has a similar structure to

glucose except for the glucose except for the – –OH on C4OH on C4

Which C is C4???Which C is C4???

H

H

H OH

CH2OH

C

HO

HO HC

OH

C

C

O

C H

D-Galactose

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Cyclic Structures (14.3)Cyclic Structures (14.3)• prevalent form of monosaccharides with 5 or 6 prevalent form of monosaccharides with 5 or 6

carbon atomscarbon atoms

• form when the hydroxyl group on C-5 reacts form when the hydroxyl group on C-5 reacts with the aldehyde group or ketone groupwith the aldehyde group or ketone group• Orgo-Chem reaction not previously mentioned: Orgo-Chem reaction not previously mentioned:

“C=O” + ROH “C=O” + ROH → hemiacetal→ hemiacetal

O O

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Drawing Cyclic Structures: Practice! Drawing Cyclic Structures: Practice! Example: GlucoseExample: Glucose

STEP 1STEP 1 Number the carbon chain and turn Number the carbon chain and turn clockwise to form a linear open chain. clockwise to form a linear open chain.

HHO

H

CH2OH

OHC

H

H

OH

OH

C

C

C

OHC

1

2

3

4

5

6

6 5 4 3 2 1

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OH

OH

OHOH

CH2OH

O

Cyclic Structure for GlucoseCyclic Structure for GlucoseSTEP 2STEP 2 Fold into a hexagon. Fold into a hexagon. • Bond the C5 –O– to C1. Bond the C5 –O– to C1. • Place the C6 group above the Place the C6 group above the

ring. ring. • Write the –OH groups on C2 & Write the –OH groups on C2 &

C4 below the ring (These are C4 below the ring (These are the C atoms that pointed down the C atoms that pointed down from Step 1). from Step 1).

• Write the –OH group on C3 Write the –OH group on C3 above the ring. above the ring.

• Write a new –OH on C1.Write a new –OH on C1.

6 5

4 1

3 2

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Cyclic Structure for GlucoseCyclic Structure for Glucose

OH

OH

OHOH

CH2OH

O

-D-Glucose -D-Glucose

OH

OH

OHOH

CH2OH

O

STEP 3 Write the new –OH on C1 • down for the form.• up for the form.

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Summary of the Formation of Summary of the Formation of Cyclic GlucoseCyclic Glucose

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MutarotationMutarotation• cyclic structures open and close. cyclic structures open and close. -D-glucose converts to -D-glucose converts to ββ-D-glucose & vice versa.-D-glucose & vice versa.• at any time, only aat any time, only a small amount of open chain forms. small amount of open chain forms.

-D-glucose D-glucose (open) -D-glucose D-glucose (open) ββ-D-glucose-D-glucose (36%) (trace)(36%) (trace) (64%) (64%)

OH

CH2OH

OH

OC

H

OH

OHOH

OH

OHOH

CH2OH

OOH

OH

OHOH

CH2OH

O

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D-fructoseD-fructose -D-fructose-D-fructoseαα-D-fructose-D-fructose

O CH2OH

OOHH

OH

OH

CH2OH

O OOHH

CH2OH

OH

OH

CH2OH

H OH

H OH

HHO

O

CH2OH

C

C

C

CCH2OH

Cyclic Structure of FructoseCyclic Structure of Fructose

• is a ketohexose.is a ketohexose.• reacts the reacts the --OH on C-5 with the C=O on C-2OH on C-5 with the C=O on C-2

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Chemical Properties of Chemical Properties of Monosaccharides (14.4)Monosaccharides (14.4)

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Reducing SugarsReducing Sugars

• are monosaccharides that oxidize to give are monosaccharides that oxidize to give a carboxylic acid. a carboxylic acid.

• undergo reaction in the Benedict’s test. undergo reaction in the Benedict’s test. • include the monosaccharides glucose, include the monosaccharides glucose,

galactose, and fructose.galactose, and fructose.

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+ Cu2O(s)

D-gluconic acidD-glucose

+ Cu2+

H OH

H OH

HHO

H OH

O

OH

CH2OH

C

C

C

C

C

H OH

H OH

HHO

H OH

O

H

CH2OH

C

C

C

C

C

Oxidation of D-GlucoseOxidation of D-Glucose

[O]

QUESTION:QUESTION: WHY CAN FRUCTOSE (A KETONE) BE OXIDIZED??? WHY CAN FRUCTOSE (A KETONE) BE OXIDIZED???

ANSWER:ANSWER: ISOMERIZATION TO AN ALDEHYDE… ISOMERIZATION TO AN ALDEHYDE…

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One Test for Glucose in Urine:One Test for Glucose in Urine: Benedict’s Test Benedict’s Test

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Reduction of MonosaccharidesReduction of Monosaccharides

• involves the involves the carbonyl group.carbonyl group.

• produces sugar produces sugar alcohols, or alcohols, or alditols.alditols.

• such as D-glucose such as D-glucose gives D-glucitol gives D-glucitol also called sorbitol.also called sorbitol.

D-Glucitol

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Learning CheckLearning CheckWrite the products of the oxidation and Write the products of the oxidation and reduction of D-mannose.reduction of D-mannose.

H

O

CH2OH

H OH

H OH

HO H

HHO

C

D-mannose

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SolutionSolution

H

O

CH2OH

H OH

H OH

HO H

HHO

C OH

O

CH2OH

H OH

H OH

HO H

HHO

C

CH2OH

H OH

H OH

HO H

HHO

CH2OH

Reduction Oxidation

D-mannitol D-mannose D-mannonic acid

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Disaccharides (14.5)Disaccharides (14.5)

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Important Disaccharides: Know These 3Important Disaccharides: Know These 3

A A disaccharidedisaccharide consists of two monosaccharides. consists of two monosaccharides.

Monosaccharides DisaccharideMonosaccharides Disaccharide

glucose + glucose glucose + glucose maltosemaltose + H + H22OO

glucose + galactoseglucose + galactose lactoselactose + H + H22OO

glucose + fructoseglucose + fructose sucrosesucrose + H + H22OO

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MaltoseMaltose

Free α-OH

A.K.A. “malt sugar”A.K.A. “malt sugar”obtained from starch obtained from starch hydrolysishydrolysisused in cereals, used in cereals, candies, and brewingcandies, and brewinglinked by an linked by an -1,4--1,4-glycosidicglycosidic bondbond formed formed from the from the −OH on C1 −OH on C1 of the 1st glucose and of the 1st glucose and −OH on C4 of the 2nd −OH on C4 of the 2nd glucoseglucosefound in both the found in both the - and - and ββ - forms - forms

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LactoseLactose

• a disaccharide of a disaccharide of ββ--DD--galactose galactose and and αα- - oror ββ-D--D-glucose.glucose.

• contains a contains a ββ -1,4- -1,4-glycosidic bondglycosidic bond..

• is found in milk is found in milk and milk products.and milk products.

α-formα-form

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SucroseSucroseSucroseSucrose or or table sugartable sugar• is obtained from sugar cane and sugar beets.is obtained from sugar cane and sugar beets.• consists of consists of αα--D-D-glucose and glucose and ββ--DD--fructose..fructose..• has an has an αα,,ββ-1,2-glycosidic bond.-1,2-glycosidic bond.

α-D-glucose

β -D-fructose

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Learning CheckLearning Check

Write the structures of the two Write the structures of the two monosaccharides that form when sucrose monosaccharides that form when sucrose is hydrolyzed.is hydrolyzed.

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SolutionSolution