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Home , Anomer, Epimer, Furanose, Hemiacetal, Heptose, Hexose

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Chem 352 - Lecture 7

Question for the Day: Unlike amino acids, which owe their diversity to a diverse array of functional groups, feature primarily two functional groups, hydroxyl groups and either a or group. What, then, do monosaccharides owe their diversity to?

Introduction to Carbohydrates 2 Carbohydrates are one of the four major classes of biological molecules, which include, ✦ Proteins ✦ Nucleic acids ✦ Carbohydrates ✦ Lipids

Chem 352, Lecture 7 - Carbohydrates X

Introduction to Carbohydrates 3

✦ Carbohydrates represent a major source of energy for living organisms.

✦ They also play major structural, protective and communication roles.

Chem 352, Lecture 7 - Carbohydrates X

Introduction to Carbohydrates 4 Carbohydrates are chemically simple, but can be structurally complex ✦ The simple have the basis stoichiometric empirical formula(CH2O)n, where n = 3 to 7 Like , simple sugars (monosaccharides) can combine to form . ✦ monosaccharides (monomer) ✦ (several monomers linked together) ✦ (many monomers linked together

Chem 352, Lecture 7 - Carbohydrates X

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9.1 Monosaccharides Monosaccharides 6 Question: Monosaccharides are What is the name ending that is ✦ either typically used to designate a ? • polyhydroxylaldehydes A. -ase ✦ or • polyhydroxylketones B. -ose Classes based on number of carbonsC. -ol ✦ (3) D. -al ✦ (4) E. -amine ✦ (5) ✦ (6) ✦ (7)

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 7

✦ L and D • Contains a chiral • Fischer projections

✦

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 8 There are different ways to designate the of a chiral center: ✦ R vs S • Rectus versus Sinister - based on the atomic mass of the substituents ✦ d (+) vs l (-) • dextrorotatory versus levorotatory - based on the bending of plane polarized light ✦ D vs L • Based on how glyceraldehyde bends plane polarized light

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 9 Trioses

✦ L and D Glyceraldehyde • Contains a chiral carbon • Fischer projections

✦ Dihydroxyacetone

Chem 352, Lecture 7 - Carbohydrates X

These are FischerMonosaccharides 10 Clicker Question:Projections Aldohexoses•Aldoses contain 4 chiral . Therefore, how many different stereoisomers are members of this group of ✦ Trioses through monosaccharides? A. 4 B. 16 C. 8 D. 12 E. 32

Chem 352, Lecture 7 - Carbohydrates X 11 L-enantiomersMonosaccharides Trioses through hexoses ✦ This figure shows only the D–enantantiomers

✦ The L-enantiomers are mirror images of the D- enantiomers.

✦ Members of an enantiomeric pair are are distinguished using the chirial carbon that is furthest from the .

✦ Most of the monosaccharides that we will encounter are the D-enantiomers.

L D

D L

L D

L D

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 12

Question:Question:•Types of optical isomers WhatWhich is the of relationshipfollowing monosaccharides between D-glucose is an and D-? of glucose: ✦ Enantiomers are stereoisomers that are mirror images A. Enantiomersof one another

B. ✦ Epimer are stereoisomers having more than one chiral carbon that differ from one another at just one chiral C. Diastereomerscarbon. D. Not stereoisomers A.✦ DiastereomersB. are stereoisomers C. having D. more than one chiral carbon that differ from one another at multiple chiral carbons.

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 13 Ketoses ✦ Trioses through hexoses

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 14

•The ones to remember ✦ Aldoses • triose ✦ D-glyceraldehyde • tetrose ‣ D- • ✦ D- • hexoses ✦ D-glucose ✦ D-mannose ✦ D-

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 15

•The ones to remember ✦ Ketoses • trisoes ✦ dihydroxyacetone • pentoses ✦ D- ✦ D- • hexoses ✦ D-

Chem 352, Lecture 7 - Carbohydrates X Monosaccharides 16

•Cyclization of aldoses and ketoses

✦ An aldehyde can react spontaneously with an to form a .

✦ A ketone can react spontaneously with an alcohol to form a hemiketal.

✦ Both of these reactions are addition reactions that lead to the formation of a new chiral carbon.

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 17

•Cyclization of aldoses and ketoses

✦ For aldoses and ketoses, this reaction occurs intramolecularly and leads to a cyclic molecule.

✦ The chiral hemiacetal or hemiketal carbon is called the anomeric carbon. ≈≈ 0% 0% • The new stereoisomers are designated α (-OH down) and β (-OH up).

✦ Haworth projections are used to represent the cyclic 21.5% 58.5% 6.5% 13.5% form of monosaccharides.36%36% 64%64%

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 18

•Cyclization of aldoses and ketoses ✦ The six-member rings are called rings ✦ The five-member rings are called rings.

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 19

•Cyclization of aldoses and ketoses ✦ pyranose rings • D-glucopyranose (aldohexose) • D-mannopyranose (aldohexose) • D-galactopyranose (aldohexose) ✦ furanose rings • D-fructofuranose (ketohexose) • D-ribofuranose (aldopentose)

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 20 Clicker Question: •Conformations of Monosaccharides Which of following conformations for β-D-glucosopyranose is predicted✦ Monosaccharides to be more stable: can have different conformations. A.

B.

Chem 352, Lecture 7 - Carbohydrates X 21

9.2 Derivatives of the Monosaccharides

Monosaccharides 22 Derivatives of monosaccharides are produced by chemical modifications. ✦ Phosphate

✦ Deoxy sugars also called sialic acid • One of the hydroxyl groups is replaced with a ✦ Amino sugars • One of the hydroxyl groups is replaced with an amino group.

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 23 ✦ The aldehyde or ketone group is reduced to an alcohol. ✦ Some are used as natural artificial sweeteners.

erythritol xylitol

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 24 Sugar acids ✦ The aldehyde can be oxidized to an acid to produce aldonic acids. • Which in turn can cyclize to form lactones. ✦ The 6-hydroxyl group on aldohexoses can also be oxidized to an acid to produce uronic acids .

Chem 352, Lecture 7 - Carbohydrates X

Glycosides 25 The hemiacetal or hemiketal carbon can go on to react with the hydroxyl group from another molecule to form an or ketal. ✦ The bond formed is called a . ✦ Glycosidic bonds are used to connect one to another.

Chem 352, Lecture 7 - Carbohydrates X 26

✦ Unlike and hemiketals, and ketals cannot open and close dynamically, • The glycosidic bond blocks a pyranose or furanose ring from reopening again.

✦ In cells, glycosidic bond formation is enzyme catalyzed and requires a source of free energy.

Chem 352, Lecture 7 - Carbohydrates X

Monosaccharides 27 Cyclized aldoses and ketoses tend to get locked into the following ring configurations

✦ pyranose rings

• 21.5%D-glucopyranose58.5% (aldohexose)6.5% 13.5% • D-mannopyranose (aldohexose) • D-galactopyranose (aldohexose)

✦ furanose rings • D-fructofuranose (ketohexose) • D-ribofuranose (aldopentose)

Chem 352, Lecture 7 - Carbohydrates X

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9.3 Oligosaccharides

Disaccharides 29 The glycosidic bond can be used to connect two monosaccharides together to form . Important disaccharides include: ✦ (obtained from )

α(1-4) glycosidic bond β-anonomer

Chem 352, Lecture 7 - Carbohydrates 3

Disaccharides 30

TheClickerQuestion: glycosidic Question: bond can be used to connect two monosacchridesWhichWhat typeanomer of glycosidicof togetherlactose bond is shown?to does form a disaccharides. have? ImportantA. α (1-4) disaccharides include: • B.Lactoseβ(1-6) C. β(1-4) (milk sugar) (1-4) glycosidic bond D. α(1-5) β α-anonomer

Chem 352, Lecture 7 - Carbohydrates 4 Disaccharides 31 The glycosidic bond can be used to connect two monosaccharides together to form disaccharides. Important disaccharides include: • (obtained from )

Chem 352, Lecture 7 - Carbohydrates 5

Disaccharides 32 The glycosidic bond can be used to connect two monosaccharides together to form disaccharides. Important disaccharides include: • (table sugar)

α1-β2 glycosidic bond

Chem 352, Lecture 7 - Carbohydrates 6

Disaccharides 33 Question: Because a hemiacetal or hemiketal can easily open to expose Whicheither anend aldehyde of the disaccharideor α-hydroxy maltose ketone, isthey the can reducing still serve end? as reducing agents for the Cu2+ ions found in Fehling’s and Benedict’s reagents. A. B.

O O

R C H + Cu2+ R C OH + Cu+

CuSO4(aq) Cu2O(s) clear blue red ppt.

‣ This reaction is used to distinguish the two monosaccharides in a as the reducing and the nonreducing ends.

Chem 352, Lecture 7 - Carbohydrates 7

Disaccharides 34 Not all disaccharides have a reducing end ✦ For example, the disaccharide sucrose contains both and acetal and a ketal, but no hemiacetal or hemiketal.

Chem 352, Lecture 7 - Carbohydrates 8

Glycosides 35 Monosaccharides also form glycosidic bonds to non- sugar. ✦ For example, , such as • ATP • UDP-glucose • NAD and NADP • FMN and FAD ✦ And sterols, such as • Ouabain

Flavin mononucleotide (FMN)

Flavin adenine dinucleotide (FAD) Chem 352, Lecture 7 - Carbohydrates 9 Glycosides 36 Ribitol is another example of a . ✦ Where the aldehyde or ketone is reduced to an alcohol.

Chem 352, Lecture 7 - Carbohydrates X

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9.4 Polysaccharides

Polysaccharides 38 The formation of glycosidic bonds can be extended to form polymers Question:of monosaccharides called glycans. ✦ HomoglycansWhat contain appears repeating to units of the same monosaccharide.distinguish the glycosidic bonds used ✦ Heteroglycans contain multiple units of different in storage homoglycans monosaccharidesfrom the glycosidic bonds used in structural homoglycans?

Chem 352, Lecture 7 - Carbohydrates 11

Polysaccharides 39

Storage forms of glucose Question Where’s Waldo? Can ✦ Starch (plants) you find the • reducing end of this Amylopectinthis • Amylopectin D-glucopyranose α(1→4) D-glucopyranose andmolecule? ✦ (animals) D-glucopyranoseAmylose α(1→6) D-glucopyranose D-glucopyranose α(1→4) D-glucopyranose Structural polysaccharides Cellulose D-glucopyranose β(1→4) D-glucopyranose ✦ Cellulose (plant) ✦ (animals)

Chitin N-acetylglucosamine β(1→4) N-acetylglucosamine

Chem 352, Lecture 7 - Carbohydrates 12

Glycosaminoglycans 40 Are heteropolysaccarides which are also called mucopolysaccharides.

Chem 352, Lecture 7 - Carbohydrates 13 41

9.4 Glycoconjugates

Glycocongugates 42 Oligo saccharides are often attached to biological molecules ✦ To proteins and peptides • Proteoglycans (connective tissue) • Peptidoglycans (bacterial cell walls) • ✦ To lipids • Glycolipids

Chem 352, Lecture 7 - Carbohydrates 15

Glycocongugates 43

To Clickerproteins Question: and peptides ✦WhatProteoglycans type of glycosidic (connective linkage tissue) connects the D- to the N-acetylglucosamine in the repeating unit of hyaluronic acid?

Hyaluronic acid A. α(1→4) B. α(1→3) C. β(1→4) D. β(1→3) E. α(1→6)

S-linked N-linked glycoprotein Chem 352, Lecture 7 - Carbohydrates 16

Glycocongugates 44

To proteins and peptides To proteins and peptides ✦ Peptidoglycans (bacterial cell wall) ✦ Peptidoglycans (bacterial cell wall)

Penicillin

Chem 352, Lecture 7 - Carbohydrates 17

Glycocongugates 45 Oligo saccharides are often attached to biological molecules ✦ To proteins and peptides • Proteoglycans (connective tissue) • Peptidoglycans (bacterial cell walls) • Glycoproteins ✦ To lipids • Glycolipids

Chem 352, Lecture 7 - Carbohydrates 18 Glycocongugates 46 To lipids ✦ Glycolipids

Question: What is your blood type?

A. A B. B C. AB D. O

Chem 352, Lecture 7 - Carbohydrates 19

Which Structures Do I Need to Know? 47

•Monosaccharide ✦ D-glucose ✦ D-galactose ✦ D-mannose ✦ D-fructose ✦ D-ribose •Disaccharides ✦ D-lactose ✦ D-maltose ✦ D-cellobiose ✦ D-sucrose

Chem 352, Lecture 7 - Carbohydrates 20

Which Structures Do I Need to Know? 48

•Monosaccharide Derivatives ✦ D-glucosamine ✦ N-acetyl-D-glucosamine ✦ D-gluconic acid ✦ D-glucuronic acid ✦ D-ribitol •Polysaccharides ✦ amylose ✦ amylopectin ✦ glycogen ✦ cellulose ✦ chitin

Chem 352, Lecture 7 - Carbohydrates 21

Questions 49 Question: Indicate which of the following terms best describes the relationship between the following isomers:

D-glyceraldehyde and dihydroxyacetone

A. anomers B. epimers C. D. constitutional isomers

Chem 352, Lecture 7 - Carbohydrates 22

Questions 50 Question: Indicate which of the following terms best describes the relationship between the following isomers:

α-D-glucose and β-D-glucose

A. anomers B. epimers C. diastereomers D. constitutional isomers

Chem 352, Lecture 7 - Carbohydrates 23 Questions 51 Question: Indicate which of the following terms best describes the relationship between the following isomers:

D-glucose and D-galactose

A. anomers B. epimers C. diastereomers D. constitutional isomers

Chem 352, Lecture 7 - Carbohydrates 24

Questions 52 Question: D-Lactose comprises D-glucose and D-galactose connected to one another by a β(1→4) glycosidic bond. Draw the structural formula for the α- of D-lactose.

Chem 352, Lecture 7 - Carbohydrates 25

Questions 53 Question: α-D-Lactose has how many stereoisomers?

A. 2 B. 32 C. 256 D. 512 E. 1023

Chem 352, Lecture 7 - Carbohydrates 26

Questions 54 Questions: Raffinose is a that is found in beans and cabbage. When eaten, it CH2OH passes undigested through the stomach OH O H to the upper intestine, where gas- OH H H producing bacteria break it down. (The O consequences of this physiological state H OH of affairs have been immortalized in the CH2 H O movie “Blazing Saddles”.) The structure H for raffinose is shown to the right. OH H OH

A. What three monosaccharides the H OH Raffinose O combine to form raffinose ? CH2OH O B. What the linkages that H OH H connect the three monosaccharides? CH2OH OH H C. Is raffinose a ?

Chem 352, Lecture 7 - Carbohydrates 27