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5B Focus on Health & Medicine: Sucrose and Artificial Sweeteners

5B Focus on Health & Medicine: Sucrose and Artificial Sweeteners

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630



CARBOHYDRATES







FIGURE 20.3 Artificial Sweeteners



CH2OH

Cl



O

H

OH



H



H



OH



H



H



CH2Cl



O



O



NH2



O



H



HO2CCH2



HO



H



CH



C

O



CH2Cl

OH



H

N



CH



NH



CH2

S



CO2CH3



O O

saccharin

(Trade name: Sweet’n Low)



H

aspartame

(Trade name: Equal)



sucralose

(Trade name: Splenda)



The sweetness of these artificial sweeteners was discovered accidentally. The sweetness

of sucralose was discovered in 1976 when a chemist misunderstood his superior, and so he

tasted rather than tested his compound. Aspartame was discovered in 1965 when a chemist

licked his dirty fingers in the lab and tasted its sweetness. Saccharin, the oldest known artificial

sweetener, was discovered in 1879 by a chemist who failed to wash his hands after working in

the lab. Saccharin was not used extensively until sugar shortages occurred during World War I.

Although there were concerns in the 1970s that saccharin causes cancer, there is no proven link

between cancer occurrence and saccharin intake at normal levels.



20.6 POLYSACCHARIDES

Polysaccharides contain three or more monosaccharides joined together. Three prevalent

polysaccharides in nature are cellulose, starch, and glycogen, each of which consists of repeating glucose units joined by glycosidic bonds.

CH2OH

H



CH2OH

H



O

H

OH



O



H

H



H



O

H

OH



CH2OH



H

H



H



OH



OH

β glycosidic linkage

cellulose—repeating structure



smi26573_ch20.indd 630



O

H



O

H

OH



H



H



OH



CH2OH

H



H

O



O

H

OH



H



H



OH



H

O



α glycosidic linkage

starch and glycogen—repeating structure



12/16/08 11:44:54 AM



POLYSACCHARIDES



631



• Cellulose contains glucose rings joined in 1→4-𝛃-glycosidic linkages.

• Starch and glycogen contain glucose rings joined in 1→4-𝛂-glycosidic linkages.



20.6A



CELLULOSE



Cellulose is found in the cell walls of nearly all plants, where it gives support and rigidity to wood,

plant stems, and grass (Figure 20.4). Wood, cotton, and flax are composed largely of cellulose.

Cellulose is an unbranched polymer composed of repeating glucose units joined in a 1→4-𝛃glycosidic linkage. The β glycosidic linkages create long linear chains of cellulose molecules that

stack in sheets, making an extensive three-dimensional array.

CH2OH

H



CH2OH

H



CH2OH

H



CH2OH

H



O

H

OH



O



H

H



H



O

H

OH



O



O



H



H



H



OH



OH

β glycosidic linkage

(shown in blue)



OH

cellulose



OH



O



H

H



H



H



H

H



O

H

OH



O

H

OH



In some cells, cellulose is hydrolyzed by an enzyme called a 𝛃-glycosidase, which cleaves all of

the β glycoside bonds, forming glucose. Humans do not possess this enzyme, and therefore





FIGURE 20.4



Cellulose



layers of microfibrils

in the plant cell wall



cell wall



cellulose fiber



plant cell



cellulose molecules

glucose



O



O

O



O

O



O

O



O



O



O

O



O

O



O



O



O



O



O

O



O



long chains of cellulose molecules hydrogen bonded together



smi26573_ch20.indd 631



12/16/08 11:44:56 AM



632



CARBOHYDRATES



cannot digest cellulose. Ruminant animals, on the other hand, such as cattle, deer, and camels,

have bacteria containing this enzyme in their digestive systems, so they can derive nutritional

benefit from eating grass and leaves.

Much of the insoluble fiber in our diet is cellulose, which passes through the digestive system

without being metabolized. Foods rich in cellulose include whole wheat bread, brown rice, and

bran cereals. Fiber is an important component of the diet even though it gives us no nutrition;

fiber adds bulk to solid waste, so that it is eliminated more readily.



20.6B



STARCH



Starch is the main carbohydrate found in the seeds and roots of plants. Corn, rice, wheat, and

potatoes are common foods that contain a great deal of starch. Starch is a polymer composed of

repeating glucose units joined in 𝛂 glycosidic linkages. The two common forms of starch are

amylose and amylopectin.

CH2OH

H



CH2OH



O

H

OH



H



H



OH



H



H

O



H

OH



H



H



OH



CH2OH

O

H

OH



H



H



OH



H



H

OH



H



H



OH



H

O



O



H



H



H



OH



H

O



O

H

OH



H



H



OH



H

O



O



H



H

OH



H



H



OH



H

O



α glycosidic linkage

(shown in red)



O

H

OH



H



H



OH



Two polysaccharide chains are connected

at a branch point along one chain.



O

CH2



CH2OH

H



H



H

OH



CH2OH

H



CH2OH

O



H



CH2OH



O



amylose

(the linear form of starch)



α glycosidic linkage

(shown in red)



H



CH2OH



O



H



H

O



CH2OH

O



H

OH



H



H



OH



H



H

O



O

H

OH



H



H



OH



H

O



amylopectin

(the branched form of starch)



Amylose, which comprises about 20% of starch molecules, has an unbranched skeleton of

glucose molecules with 1→4-𝛂-glycoside bonds. Because of this linkage, an amylose chain

adopts a helical arrangement, giving it a very different three-dimensional shape from the linear

chains of cellulose (Figure 20.5).

Amylopectin, which comprises about 80% of starch molecules, consists of a backbone of glucose

units joined in 𝛂 glycosidic bonds, but it also contains considerable branching along the chain.

The linear linkages of amylopectin are formed by 1→4-𝛂-glycoside bonds, similar to amylose.

Both forms of starch are water soluble. Since the OH groups in these starch molecules are not

buried in a three-dimensional network, they are available for hydrogen bonding with water molecules, leading to greater water solubility than cellulose.

Both amylose and amylopectin are hydrolyzed to glucose with cleavage of the glycosidic bonds.

The human digestive system has the necessary amylase enzymes needed to catalyze this process.

Bread and pasta made from wheat flour, rice, and corn tortillas are all sources of starch that are

readily digested.



smi26573_ch20.indd 632



12/16/08 11:44:57 AM



POLYSACCHARIDES



633







FIGURE 20.5 Starch—Amylose and Amylopectin



wheat kernels



wheat stalks



amylopectin



PROBLEM 20.23



amylose



Label all acetal carbons in the structure of amylopectin drawn at the beginning of Section 20.6B.



20.6C



GLYCOGEN



Glycogen is the major form in which polysaccharides are stored in animals. Glycogen, a

polymer of glucose containing 𝛂 glycosidic bonds, has a branched structure similar to amylopectin, but the branching is much more extensive (Figure 20.6).





FIGURE 20.6 Glycogen



branching



glycogen in liver cells



glycogen



smi26573_ch20.indd 633



12/16/08 11:44:57 AM



634



CARBOHYDRATES



Glycogen is stored principally in the liver and muscle. When glucose is needed for energy in the

cell, glucose units are hydrolyzed from the ends of the glycogen polymer, and then further metabolized with the release of energy. Because glycogen has a highly branched structure, there are many

glucose units at the ends of the branches that can be cleaved whenever the body needs them.



PROBLEM 20.24



Cellulose is water insoluble, despite its many OH groups. Based on its three-dimensional

structure, why do you think this is so?



20.7 FOCUS ON THE HUMAN BODY

USEFUL CARBOHYDRATE DERIVATIVES

HEALTH NOTE



Many other simple and complex carbohydrates with useful properties exist in the biological world. Several are derived from monosaccharides that contain an amino (NH2) or amide

(NHCOCH3) group in place of an OH group. Examples include d-glucosamine, the most

abundant amino sugar in nature, and N-acetyl-d-glucosamine (NAG). Other carbohydrates

are derived from d-glucuronate, which contains a carboxylate anion, COO–, in place of the

CH2OH group of the typical monosaccharide skeleton.

CH2OH

H



O

H

OH



H

H



NH2



D-glucosamine



20.7A



OH



H



H



HO



COO−



CH2OH

O

H

OH



HO



OH



H

H



H



H



NHCOCH3



N-acetyl-D-glucosamine



O

H

OH



OH



H



HO



H

H



OH



D-glucuronate



GLYCOSAMINOGLYCANS



Glycosaminoglycans (GAGs) are a group of unbranched carbohydrates derived from alternating amino sugar and glucuronate units. Glycosaminoglycans form a gel-like matrix that acts as a

lubricant, making them key components in connective tissue and joints.



Injections of heparin in an intravenous line keep the line from clogging

with blood.



PROBLEM 20.25



Examples include hyaluronate, which is found in the extracellular fluid that lubricates joints and

the vitreous humor of the eye; chondroitin, a component of cartilage and tendons; and heparin,

which is stored in the mast cells of the liver and other organs and prevents blood clotting (Figure

20.7). While the monosaccharide rings of hyaluronate and chondroitin are joined by β glycosidic

linkages (shown in blue), those of heparin are joined by α glycosidic linkages (shown in red).

Classify the glycosidic linkages in chondroitin and heparin (Figure 20.7) as α or β, and use

numbers to designate their location.



20.7B



CHITIN



Chitin, the second most abundant carbohydrate polymer, is a polysaccharide formed from

N-acetyl-d-glucosamine units joined together in 1→4-𝛃-glycosidic linkages. Chitin is identical in structure to cellulose, except that each OH group at C2 is now replaced by NHCOCH3.

The exoskeletons of lobsters, crabs, and shrimp are composed of chitin. Like cellulose, chitin

chains are held together by an extensive network of hydrogen bonds, forming water-insoluble

sheets.



smi26573_ch20.indd 634



12/16/08 11:45:01 AM



FOCUS ON THE HUMAN BODY: USEFUL CARBOHYDRATE DERIVATIVES



HEALTH NOTE







635



FIGURE 20.7 Glycosaminoglycans

CH2OH



O



H



H

OH



O



H



COO−



H



O

HO



H



H

NHCOCH3



H



H

H



O



H



OH

hyaluronate



CH2OH

−O



COO−

O



H



H

OH



H



H



OH



O



3SO



O



H

H



O



H



H



H



H



NHCOCH3



chondroitin



COO−



Both chondroitin and glucosamine

are sold as dietary supplements for

individuals suffering from osteoarthritis. On-going research is examining the role of these supplements

in replacing and rebuilding lost joint

cartilage in the hope of halting or

reversing the progression of arthritis.



CH2OSO3−

O



H



O



H



H



H

OH



H



H



OSO3−



O



H



H

OH



H



H



NHSO3−



O



heparin



Hyaluronates form viscous solutions that act as lubricants in the fluid around joints. They

also give the vitreous humor of the eye its gelatin-like consistency. Chondroitin strengthens

cartilage, tendons, and the walls of blood vessels. Heparin is an anticoagulant.



CH2OH



H



O

H

OH



O



H

H



H



The rigidity of a crab shell is due

to chitin, a high molecular weight

carbohydrate molecule. Much of

the D-glucosamine sold in over-thecounter dietary supplements comes

from shellfish.



H



CH2OH

H



CH2OH



H



CH2OH



β glycosidic linkage

(shown in blue)



O

H

OH



O



H

OH



O



H

H



H



H



H

H



O



O

H

OH



O



H

H



H



NHCOCH3



NHCOCH3



NHCOCH3



NHCOCH3



chitin



hydrolysis



CH2OH

H



O

H

OH



OH



H



HO



H

H



NH2



D-glucosamine



smi26573_ch20.indd 635



12/16/08 11:45:04 AM



636



CARBOHYDRATES



Chitin-based coatings have found several commercial applications, such as extending the shelf

life of fruits. Processing plants now convert the shells of crabs, lobsters, and shrimp to chitin and

various derivatives for use in many consumer products. Complete hydrolysis of the glycoside and

amide bonds in chitin forms the dietary supplement d-glucosamine.

Suppose that chitin contained α glycosidic linkages. Draw a portion of the resulting

polysaccharide that contains four N-acetyl-d-glucosamine units joined together.



PROBLEM 20.26



20.8 FOCUS ON THE HUMAN BODY

BLOOD TYPE

Human blood is classified into one of four types using the ABO system discovered in the early

1900s by Karl Landsteiner. There are four blood types—A, B, AB, and O. An individual’s blood

type is determined by three or four monosaccharides attached to a membrane protein of red blood

cells. These monosaccharides include:

CH2OH

OH



O

H

OH



H



H



H



OH

H



OH



D-galactose



CH2OH



H

H



O

CH3

H



H



OH



OH



OH

OH



H



H



L-fucose



O

H

OH



OH



CH2OH

H



H

OH



H



OH



NHCOCH3



N-acetyl-D-glucosamine



O

H

OH



H



H



H

OH



H



NHCOCH3



N-acetyl-D-galactosamine



Each blood type is associated with a different carbohydrate structure, as shown in Figure 20.8.

Three monosaccharides occur in all blood types—N-acetyl-d-glucosamine, d-galactose, and

l-fucose. Type A blood contains a fourth monosaccharide, N-acetyl-d-galactosamine, and type

B blood contains an additional d-galactose unit. Type AB blood has both type A and type B

carbohydrates.



HEALTH NOTE



The short polysaccharide chains distinguish one type of red blood cell from another, and signal

the cells about foreign viruses, bacteria, and other agents. When a foreign substance enters the

blood, the body’s immune system uses antibodies to attack and destroy the invading substance so

that it does the host organism no harm.

Knowing an individual’s blood type is necessary before receiving a blood transfusion. Because

the blood of an individual may contain antibodies to another blood type, the types of blood that

can be given to a patient are often limited. An individual with blood type A produces antibodies

to type B blood, and an individual with blood type B produces antibodies to type A blood. Type

AB blood contains no antibodies to other blood types, while type O blood contains antibodies to

both types A and B. As a result:

• Individuals with type O blood are called universal donors because no antibodies to type

O are produced by those with types A, B, and AB blood. Type O blood can be given to

individuals of any blood type.

• Individuals with type AB blood are called universal recipients because their blood

contains no antibodies to blood types A, B, or O. Individuals with type AB blood can

receive blood of any type.



The blood type of a blood donor and

recipient must be compatible, so

donated blood is clearly labeled with

the donor’s blood type.



smi26573_ch20.indd 636



Table 20.2 lists what blood types can be safely given to an individual. Blood must be carefully

screened to make sure that the blood types of the donor and recipient are compatible. Should

the wrong blood type be administered, antibodies of the immune system will attack the foreign

red blood cells, causing them to clump together, which can block blood vessels and even result

in death.



12/16/08 11:45:08 AM



FOCUS ON THE HUMAN BODY: BLOOD TYPE







637



FIGURE 20.8 Carbohydrates and Blood Types



Type A



N-acetyl-Dglucosamine



D-galactose



N-acetyl-Dgalactosamine



L-fucose



Type B



N-acetyl-Dglucosamine



D-galactose



D-galactose



L-fucose



Type O



N-acetyl-Dglucosamine



D-galactose



L-fucose



Each blood type is characterized by a different polysaccharide that is covalently bonded to a

membrane protein of the red blood cell. There are three different carbohydrate sequences, one

each for A, B, and O blood types. Blood type AB contains the sequences for both blood type A

and blood type B.



TABLE 20.2



smi26573_ch20.indd 637



Compatibility Chart of Blood Types



Blood Type



Can Receive Blood Type:



Can Donate to Someone

of Blood Type:



A



A, O



A, AB



B



B, O



B, AB



AB



A, B, AB, O



AB



O



O



A, B, AB, O



PROBLEM 20.27



List two structural features that distinguish l-fucose from the other monosaccharides we have

seen in naturally occurring molecules.



PROBLEM 20.28



How do N-acetyl-d-glucosamine and N-acetyl-d-galactosamine differ in structure? Are these

two compounds constitutional isomers or stereoisomers? Explain your choice.



12/16/08 11:45:12 AM



638



CARBOHYDRATES



CHAPTER HIGHLIGHTS

KEY TERMS

Alditol (20.4)

Aldonic acid (20.4)

Aldose (20.2)

α Anomer (20.3)

β Anomer (20.3)

Anomeric carbon (20.3)

Benedict’s reagent (20.4)

Carbohydrate (20.1)

Disaccharide (20.1)



d Monosaccharide (20.2)

α Glycoside (20.5)

β Glycoside (20.5)

Glycosidic linkage (20.5)

Haworth projection (20.3)

Hexose (20.2)

Ketose (20.2)

l Monosaccharide (20.2)

Monosaccharide (20.1)



Mutarotation (20.3)

Nonreducing sugar (20.4)

Pentose (20.2)

Polysaccharide (20.1)

Reducing sugar (20.4)

Tetrose (20.2)

Triose (20.2)



KEY REACTIONS

[1]



Reduction of monosaccharides to alditols (20.4A)

CHO



CH2OH



H



C



OH



HO



C



H



H



C



OH



H



C



OH



+



H2



Pd



H



C



OH



HO



C



H



H



C



OH



H



C



OH



CH2OH



CH2OH

alditol



[2] Oxidation of monosaccharides to aldonic acids (20.4B)

COOH



CHO

H



C



OH



HO



C



H



H



C



OH



H



C



OH



+



2 Cu2+

(blue)



H



C



OH



HO



C



H



H



C



OH



H



C



OH



−OH



CH2OH



+



Cu2O

(brick-red)



CH2OH

aldonic acid



[3] Hydrolysis of disaccharides (20.5)

CH2OH

H



O

H

OH



H



OH

H



smi26573_ch20.indd 638



OH



CH2OH



CH2OH

H



H

O



O

H

OH



+



H

OH



H



OH



H



H

H2O



O

H

OH



CH2OH

H

+



H

OH



OH

H



OH



H



O

H

OH



H



H

OH



HO

H



OH



12/16/08 11:45:12 AM



CHAPTER HIGHLIGHTS



639



KEY CONCEPTS

❶ What are the three major types of carbohydrates? (20.1)

• Monosaccharides, which cannot be hydrolyzed to simpler

compounds, generally have three to six carbons with a

carbonyl group at either the terminal carbon or the carbon

adjacent to it. Generally, all other carbons have OH groups

bonded to them.

• Disaccharides are composed of two monosaccharides.

• Polysaccharides are composed of three or more

monosaccharides.

❷ What are the major structural features of

monosaccharides? (20.2)

• Monosaccharides with a carbonyl group at C1 are called

aldoses and those with a carbonyl at C2 are called ketoses.

Generally, OH groups are bonded to every other carbon.

The terms triose, tetrose, and so forth are used to indicate

the number of carbons in the chain.

• The acyclic form of monosaccharides is drawn with Fischer

projection formulas. A d sugar has the OH group of the

chirality center farthest from the carbonyl on the right side.

An l sugar has the OH group of the chirality center farthest

from the carbonyl on the left side.

❸ How are the cyclic forms of monosaccharides drawn?

(20.3)

• In aldohexoses the OH group on C5 reacts with the

aldehyde carbonyl to give two cyclic hemiacetals called

anomers. The acetal carbon is called the anomeric carbon.

The α anomer has the OH group drawn down for a d sugar

and the β anomer has the OH group drawn up.

anomeric carbon



anomeric carbon

CH2OH



CH2OH

H



O

H

OH



H



H



HO



OH

H



H



OH



α anomer



O

H

OH



OH



H



HO



H

H



OH



β anomer



❹ What reduction and oxidation products are formed from

monosaccharides? (20.4)

• Monosaccharides are reduced to alditols with H2 and Pd.

• Monosaccharides are oxidized to aldonic acids with

Benedict’s reagent. Sugars that are oxidized with Benedict’s

reagent are called reducing sugars.

❺ What are the major structural features of disaccharides?

(20.5)

• Disaccharides contain two monosaccharides joined by

an acetal C O bond called a glycosidic linkage. An

α glycoside has the glycosidic linkage oriented down and

a β glycoside has the glycosidic linkage oriented up.



smi26573_ch20.indd 639



• Disaccharides are hydrolyzed to two monosaccharides by

the cleavage of the glycosidic C O bond.

• Lactose (the principal disaccharide in milk) and sucrose

(table sugar) are common disaccharides.

❻ What are the differences in the polysaccharides cellulose,

starch, and glycogen? (20.6)

• Cellulose, starch, and glycogen are all polymers of the

monosaccharide glucose.

• Cellulose is an unbranched polymer composed of repeating

glucose units joined in 1→

1→44-β

β-glycosidic linkages.

Cellulose forms long chains that stack in three-dimensional

sheets. The human digestive system does not contain the

needed enzyme to metabolize cellulose.

• There are two forms of starch—amylose, which is

an unbranched polymer, and amylopectin, which is a

branched polysaccharide polymer. Both forms contain

1→44-α

α-glycosidic linkages, and the polymer winds in a

helical arrangement. Starch is digestible since the human

digestive system has the needed amylase enzyme to catalyze

hydrolysis.

• Glycogen resembles amylopectin but is more extensively

branched. Glycogen is the major form in which

polysaccharides are stored in animals.

❼ Give examples of some carbohydrate derivatives that

contain amino groups, amides, or carboxylate anions.

(20.7)

• Glycosaminoglycans are a group of unbranched

carbohydrates derived from amino sugar and glucuronate

units. Examples include hyaluronate, which forms a gellike matrix in joints and the vitreous humor of the eye;

chondroitin, which is a component of cartilage and tendons;

and heparin, an anticoagulant.

• Chitin, a polymer of N-acetyl-acetyl-d

d-glucosamine, forms the

hard exoskeletons of crabs, lobsters, and shrimp.

❽ What role do carbohydrates play in determining blood

type? (20.8)

• Human blood type—A, B, AB, or O—is determined by

three or four monosaccharides attached to a membrane

protein on the surface of red blood cells. There are three

different carbohydrate sequences, one for each of the A, B,

and O blood types. Blood type AB contains the sequences

for both blood type A and blood type B. Since the blood of

an individual may contain antibodies to another blood type,

blood type must be known before receiving a transfusion.



12/16/08 11:45:12 AM



640



CARBOHYDRATES



PROBLEMS

Selected in-chapter and end-of-chapter problems have brief answers provided in Appendix B.



Monosaccharides

20.29

20.30

20.31



20.32



20.33

20.34

20.35

20.36

20.37



20.41



What is the difference between an aldose and a ketose?

Give an example of each type of carbohydrate.

What is the difference between a tetrose and a pentose?

Give an example of each type of carbohydrate.

Draw the structure of each type of carbohydrate.

a. an l-aldopentose

c. a five-carbon alditol

b. a d-aldotetrose

Draw the structure of each type of carbohydrate.

a. a d-aldotriose

c. a four-carbon aldonic acid

b. an l-ketohexose

What is the difference between a Fischer projection and a

Haworth projection?

What is the difference between an α anomer and a β

anomer?

Are α-d-glucose and β-d-glucose enantiomers? Explain

your choice.

Are d-fructose and l-fructose enantiomers? Explain your

choice.

Classify each monosaccharide by the type of carbonyl

group and the number of carbons in the chain.

CH2OH

CHO

a.

b.

c.

CHO

HO



C



H



HO



C



H



HO



C



H



HO



C



H



HO



C



H



H



C



OH



CH2OH



C



O



H



C



OH



HO



C



H



Consider monosaccharides A, B, and C.

CHO



20.42



20.43



CH2OH



C



H



CH2OH



H



C



OH



H



C



OH



HO



C



H



H



C



OH



HO



C



H



HO



C



H



HO



C



H



CH2OH



CH2OH



20.39



20.40



For each compound in Problem 20.37: [1] label all the

chirality centers; [2] classify the compound as a d or l

monosaccharide; [3] draw the enantiomer; [4] draw a

Fischer projection.

For each compound in Problem 20.38: [1] label all the

chirality centers; [2] classify the compound as a d or l

monosaccharide; [3] draw the enantiomer; [4] draw a

Fischer projection.



smi26573_ch20.indd 640



C



O



C



OH



C



OH



H



C



OH



H



C



OH



HO



C



H



H



CH2OH



CH2OH



CH2OH



A



B



C



a. Which two monosaccharides are stereoisomers?

b. Identify two compounds that are constitutional

isomers.

c. Draw the enantiomer of B.

d. Draw a Fischer projection for A.

Consider monosaccharides D, E, and F.

CHO



CH2OH



H



C



OH



C



O



HO



C



H



H



C



OH



HO



C



H



HO



C



H



H



C



OH



HO



C



H



H



C



OH



CHO



CH2OH



CH2OH



CH2OH



D



E



F



a. Which two monosaccharides are stereoisomers?

b. Identify two compounds that are constitutional

isomers.

c. Draw the enantiomer of F.

d. Draw a Fischer projection for D.

Using Haworth projections, draw the α and β anomers of

the following d monosaccharide.

CHO



Classify each monosaccharide by the type of carbonyl

group and the number of carbons in the chain.

CHO

CHO

CHO

b.

c.

a.

HO



CH2OH



H



CH2OH



20.38



CHO



HO



C



H



H



C



OH



HO



C



H



H



C



OH



CH2OH



20.44



Using Haworth projections, draw the α and β anomers of

the following d monosaccharide.

CHO

H



C



OH



H



C



OH



HO



C



H



H



C



OH



CH2OH



12/16/08 11:45:12 AM



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