Done by: Raghda Al-Droubi

16

16-2

06% of our diet is Carbohydrates

Ex: rice, potato, bread and sweet.

16

16-4

Carbohydrates Learning Objectives

1. What Are the Structures and the

Stereochemistry of Monosaccharides?

2. How Do Monosaccharides React?

3. What are Disaccharides ?

4. What Are Some Important

Oligosaccharides?

5. What Are the Structures and Functions of

Polysaccharides?

6. What Are Glycoproteins?

16

16-5

Carbohydrates• Carbohydrate: a polyhydroxyaldehyde or

polyhydroxyketone, or a substance that contain

C:H:O and H:O ratio is 2:1 (as water)

• ~ose designate sugars.

• Monosaccharide: a carbohydrate that cannot be

hydrolyzed to a simpler carbohydrate

• they have the general formula CnH2nOn, where n

varies from 3 to 8

• Monosaccharide maybe aldose: a monosaccharide containing an aldehyde

group

ketose: a monosaccharide containing a ketone group

. Enzyme تعتبر Ase كل كلمة اخرها

Lactase = Enzyme

Lactose = Sugar

Lactose Intolerance = deficiency of Lactase enzyme.

16

16-6

Monosaccharides• Monosaccharides are classified by their number

of carbon atoms

he xose

he ptose

octose

triose

te trose

pe ntose

FormulaName

C3 H6 O3

C4 H8 O4

C5 H1 0 O5

C6 H1 2 O6

C7 H1 4 O7

C8 H1 6 O8

16

16-7

Fischer Projections• Fischer projection: a two dimensional

representation for showing the configuration of

tetrahedral

• horizontal lines represent bonds projecting forward

• vertical lines represent bonds projecting to the rear

D-Gl yce ral dehyde

CHO

CH OH

CH2 OH

D-Gl yce ral dehyde

conve rt to a Fische rproje cti on

H OH

CHO

CH2 OH

Fisher projection

Right ( D) Left ( L)

L or D الموجودة على الكربونة قبل الاخٌرة بقسمها الى hydroxyl group حسب ال

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16-8

Monosaccharides• There are only two trioses

• aldo- and keto- are often omitted and these compounds

are referred to simply as trioses; although this

designation does not tell the nature of the carbonyl

group, it at least tells the number of carbons

Dihydroxyacetone(a ketotriose)

Glyceraldehyde(an aldotriose)

C H O

C H O H

C H 2 O H

C H 2 O H

C = O

C H 2 O H

aldehyde CHO C=O ketone

Aldotriose --- (aldo) for aldehyde group ,, (triose ) for 3 carbon atoms.

Ketotriose --- (keto) for ketone group ,, (triose) for 3 carbon atoms.

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16-9

D- Aldoses

D-Glyceraldehyde الاصل تبعهم D-Aldoses *

Glucose is Aldohexose

كربونات 0ٌحتوي على مجموعة الدهاٌد و

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D-Ketoses

D-Dihydroxyacetone الاصل تبعهم D-Ketoses *

Fructose is keyohexose

كربونات. 0ٌحتوي على مجموعة كٌتون و

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Hexoses of physiologic importance.

Sugar Source Importance Clinical

Significance

D-Glucose Fruit juices.

Hydrolysis of

starch, cane

sugar,

maltose, and

lactose.

The sugar of

the body.

carried by

blood the

principal one

used by the

tissues

Present in the

urine (glucosuria)

in diabetes

mellitus owing to

raised blood

glucose

(hyperglycemia)

D-Fructose Fruit juices.

Honey.

Hydrolysis of

cane sugar

and of inulin.

Can be

changed to

glucose in the

liver

Hereditary fructose

intolerance

leads to fructose

accumulation

and hypoglycemia.

رات فً الجسم هو الاسهل.امتصاص ال كربوهٌد

. Small Intestine ٌتم امتصاص الكربوهٌدرات فً ال

D-Glucose is:

*The easiest source for energy.

*The only one circulating to all tissues. خلاٌا الدماغ و العضلات و الكبد و باقً خلاٌا الجسم

سٌصلهم غلوكوز.

الانسولٌن هو الً بدخل ال غلوكوز على الخلاٌا.

عند مرٌض السكري ٌبحثوا عن سكر فً البول .

Lactose (milk sugar) = glucose + galactose.

D-Fructose is sweeter than glucose.

D-Mannose: Carbohydrates in cell membrane act as markers.

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Hexoses of physiologic importance.

Sugar Source Importance Clinical

Significance

D-Galactose Hydrolysis

of lactose.

Can be changed to

glucose in the liver

and metabolized.

Synthesized in the

mammary gland to

make the lactose of

milk. A constituent of

glycolipids and

glycoproteins.

Failure to

metabolize

leads to

galactosemia

and cataract.

D-Mannose Hydrolysis

of plant

mannans

and gums.

A constituent of many

glycoproteins.

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16-13

Sucralose ( Splenda )• Discovered in 1976, sucralose is 600 times sweeter

than sugar and does not metabolize to produce

energy, thus it does not contain calories. It is the only

low calorie sweetener that is made from sugar, which

has been changed so passes through the body

unchanged and unmetabolized. Substituting for three

alcohol groups on the sugar

molecule with 3 chlorine atoms.

*Sucralose is artificial

*Sucrose + 3 Cl atoms = Sucralose

zero calorie الهدف منه بس الطعم

Aspartame متل ال

**Why Aspartame is zero calorie ?

Because it is Amino Acid consist of Aspartic acid and methyl ester of

phenylalanine و هدول التنٌن ما الهم علاقة بالسكر بالتالً همه خالٌٌن من السعرات الحرارٌة

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16-14

Stevia• Stevia is a sweetener and sugar substitute extracted

from the leaves of the plant species Stevia

rebaudiana which is grown in Brazil and Paraguay.

• Stevia has no calories, and it is 200 times sweeter

than sugar in the same concentration.

بعطٌنً حلاوة اذًا مو سكر .نبات بس

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16-15

Monosaccharides• Glyceraldehyde contains a stereocenter (chiral C)

and exists as a pair of stereoisomers

(enantiomers)

L-Gl yce ral dehydeD-Gl yce ral dehyde

CHO

C

CHO

CH OH

CH2 OH CH2 OH

HHO

Note: Number of stereoisomers= 2n

n is the number of stereocenters (chiral carbon)

16

16-16

D, L Monosaccharides• According to the conventions proposed by

Fischer

• D-monosaccharide: a monosaccharide that, when

written as a Fischer projection, has the -OH on its

penultimate carbon (the one before the last= the

highest numbered chiral carbon) on the right

• L-monosaccharide: a monosaccharide that, when

written as a Fischer projection, has the -OH on its

penultimate carbon (the one before the last= the

highest numbered chiral carbon) on the left

Chiral carbon: is the carbon bounded to 4 different group.

حسب موقع مجوعة الهٌدروكسل على الكربونة قبل الاخٌرة . L or D بحدد انه

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16-17

The four aldotetroses• Enantiomers: stereoisomers that are mirror

images .• example: D-erythrose and L-erythrose are enantiomers

• Diastereomers: stereoisomers that are not mirrorimages .• Epimers: diastereomers that differ from each other in

configuration of one chiral carbon

• example: D-erythrose and D-threose are diastereomers

CHO

CH2 OH

OHH

OHH

CHO

CH2 OH

HHO

HHO

CHO

CH2 OH

HHO

OHH

CHO

CH2 OH

OHH

HHO

D-Erythrose L-Erythrose D-Threose L-Threose

Mirrorpl ane

Mirrorpl ane

Enantiomers: D and L of the same structure.

Diastereomers: totally different,,, ex : glucose and fructose –

Glucose and galactose

Epimers: 2 compound differ in one carbon.

. Epimers فقط كربونة وحدة بالتالً بسمٌهم Galactose و ال Glucose الفرق بٌن ال

Glucose and Mnnose are Epimers.

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16-18

• Following are the two most common

D-aldotetroses and the two most common

D-aldopentoses

D, L Monosaccharides

D-Erythrose D-Threose D-Ri bose 2-De oxy-D-ri bose

CHO

CH2 OH

OHH

OHH

CHO

CH2 OH

HHO

OHH

CHO

CH2 OH

OHH

OHH

OHH

CHO

CH2 OH

HH

OHH

OHH

D-Ribose exists in RNA.

2-Deoxy-D-Ribose exists in DNA.

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16-19

• The three most common D-aldohexoses. Note that the

third of these is an amino sugar.

• also shown is the most common 2-keto-D-hexose

CHO

CH2 OH

OHH

HHO

OHH

OHH

D-GlucosamineD-Glucose D-Galactose

CHO

CH2 OH

OHH

HHO

HHO

OHH

CHO

CH2 OH

NH2H

HHO

OHH

OHH

CH2 OH

C

CH2 OH

O

HHO

OHH

OHH

D-Fructose

D-Glucose and D-Galactose are Epimers (similar structure but differ in one

carbon).

D-Glucosamine amino group اضفنا واحد

D-Fructose contain keto group.

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16-20

Cyclic Structure• Monosaccharides especially pentoses and

hexoses have -OH and C=O groups in the same molecule and exist almost entirely as five- and six-membered cyclic hemiacetals or hemiketal• Hemiacetal : bond between C=O on C1 (aldehyde) and

-OH on last chiral C

• Hemiketal: bond between C=O on C2 (ketone) and -OH on last chiral C

• Cyclic strusture will display extra chiral carbon (anomeric carbon)

• anomeric carbon: the new stereocenter resulting from cyclic hemiacetal or hemiketal formation• anomers: monosaccharides that differ in configuration

only at their anomeric carbons

Cyclic Structure: sugar exists in Ring structure.

Reaction between carbon 1 and OH on the last chiral carbon.

Anomers: alpha and beta structure of cyclic sugar.

16

16-21

Haworth Projections• Haworth projections

• five- and six-membered hemiacetals are represented as

planar pentagons or hexagons

• most commonly written with the anomeric carbon on

the right and the hemiacetal oxygen to the back right

• the designation -means that -OH on the anomeric

carbon is cis to the terminal -CH2OH (above the plane);

- means that it is trans to the terminal -CH2OH (below

the plane)

• The OH groups on the right in Fischer below in

Haworth. Those to the left in Fischer upward in

Haworth.

• Counting is clockwise starting from anomeric carbon

Epimers in Haworth projection: different in the position of the hydroxyl group on

one carbon atom (above and below).

16

16-22

Haworth Projections

Reaction between aldehyde group and carbon #5

Beta (β): OH above the plane of the ring.

Alpha (α): OH below the plane of the ring.

. Anomeric carbon على الOH حسب موقع ال βو αبنقسم الى

16

16-23

Haworth Projections• a six-membered hemiacetal ring is shown by the infix -

pyran-• a five-membered hemiacetal ring is shown by the infix -

furan-

OOPyranFuran

• Pyranose: a six-membered ring sugar

• Furanose: a five-membered ring sugar

.Furan او Pyran اما Haworth projection الاصل من ال

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16-24

Haworth Projections• Five-membered rings are so close to being planar that

Haworth projections are adequate to represent

furanoses.

O

OH()

H

HHO OH

H H

-D-Ri bofuranose

(-D-Ri bose)

O

H

OH( )

HHO OH

H H

-D-Ri bofuranose(-D-Ri bose)

HOCH2 HOCH2

Ribose ًسكر خماس

16

16-25

Comparison of the Fischer and Haworth Representations

Fisher: straight formula and the OH group between carbon 1 and 5.

Anomeric Carbon

16

16-26

Comparison of the Fischer and

Haworth Representations

16

16-27

Oxidation • Reducing sugar: one that reduces an oxidizing

agent• Reducing sugar: has free aldehyde or ketone group

• oxidation of a cyclic hemiacetal form gives a lactone

• when the oxidizing agent is Tollens’ reagent (used to detect reducing sugars), Ag precipitates as a silver mirror

OH-

H OH

HHO

HOH

H

CH2 OH

O

O

A lactone(a cyclic es ter)

OH

H OH

HHO

HH

OH

H

CH2 OH

O

A cyclic he mi ace tal

Ag( NH3 ) 2++ Ag+

A reducing sugar is any sugar that is capable of acting as a reducing

agent because it has a free aldehyde group or a free ketone group. All

Silver

nitrate

Silver ترسبب

و بعطٌنً مرآة فضٌة

monosaccharaides are reducing sugars, along with some

disaccharides (lactose and maltose).

Reducing properties تعتمد على وجود مجموعة الادهاٌد او الكٌتون فً التفاعل .

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16-28

Ascorbic Acid (Vitamin C)• L-Ascorbic acid (vitamin C) is synthesized both

biochemically and industrially from oxidation of

D-glucose

CHO

CH2 OH

OHH

HHO

OHH

OHH

D-Gl ucose

CH2 OH

OHH

HHO

O

OH

both bioche mi aland i ndustrial

synthese s

L-Ascorbic aci d (Vitamin C)

O

Reducing properties:

Property of reducing sugar الغلوكوز فً البول و ذلك اعتمادًا على ال على بتعمل كشف

Reducing test: detection of glucose and ascorbic acid –any substance acts as a

reduction--

16

16-29

Ascorbic Acid (Vitamin C)• L-Ascorbic acid is very easily oxidized to L-

dehydroascorbic acid

• both are physiologically active and are found in most

body fluids

CH2 OH

OHH

HO

O

O

L-Ascorbic aci d (Vitamin C)

L-De hydroascorbi c acid

oxidation

re duction

CH2 OH

OHH

HHO

O

OH

O O

D-Glucose ٌتم استخلاصه من ال Ascorbic acid

. C ارخص فٌتامٌن هوه فٌتامٌن

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16-30

Reduction • The carbonyl group of a monosaccharide can be

reduced to a hydroxyl group by a variety of reducing agents

• reduction of the CHO group of a monosaccharide gives

a polyhydroxy compound called an alditol

Ni+

D-Glucitol(D-Sorbitol )

D-Gl ucose

H2

CHO

CH2 OH

OHH

HHO

OHH

OHH

CH2 OH

CH2 OH

OHH

HHO

OHH

OHH

Commercial sweetener in

sugarless gum and candy

D-Sorbitol derived from D-Glucose.

. OH الى CHO بسبب تحول مجموعة Ol اخر المركب

Free sugar gum contain either D-Sorbitol or D-Xylitol.

16

16-31

Reduction Reactions

16

16-32

Formation of deoxy sugars16

16-32

Formation of deoxy sugars

ما علٌها 2كربونة رقم

Oxygen.

ما علٌها 6كربونة رقم

Oxygen.

Deoxy means without Oxygen.

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16-33

Phosphoric Esters• Phosphoric esters are particularly important in

the metabolism of sugars

• phosphoric esters are frequently formed by transfer of

a phosphate group from ATP

H

H OH

HHO

HOH

OH

H

CH2 OH

O

-D-glucose

-O- P-OPOPO-Adenosine

O

O- O-

O

O-

O

+

+ -OPOPO-Adenosine

O-

O

O-

O

ATP

H

H OH

HHO

HOH

OH

H

CH2 OPO32 -

O

-D-glucose-6-phosphate

ADP

enzyme

First pathway in carbohydrates is Glycolysis.

Phosphorylation for Glucose in presence of Hexokinase enzyme produces

Glucose-6-phosphate.

. ADP and Glucose-6-phosphate الى الغلوكوز و بنتجATP مجموعة الفسفور بتنتقل من ال

؟عشان ٌضل الغلوكوز جوّا الخلٌة. Phosphorylation لٌه بنعمل

Glucose-6-phosphate has negative charge.

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16-34

Formation of Glycosides• Glycoside: a carbohydrate in which the -OH of

the anomeric carbon is replaced by -OR

• those derived from furanoses are furanosides; those

derived from pyranoses are pyranosides

• O-glycosidic bond: the bond in the glycoside, between

the anomeric carbon and the -OR group

O

CH2 OH

H

OH

HH

HOH

OHH

OCH3

Methyl -D-

gl ucopyranosi de

O

CH2 OH

H

OH

HH

HOH

OHH

OH

+ CH3 OH + H2 O

gl ycosidicbond

-D-gl ucopyranose

(methyl

alcohol)

Glycosidic bond might be between Oxygen and:

1-methyl group or 2-nitrogen group or 3-amino group.

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16-35

Amino Sugars

O

CH2 OH

OH

OH

HO

NH-C- CH3

N-Acetyl-D-glucosamine

OCH2 OH

HOHO

NHOH

C

CH3

O

O

CH2 OH

O

OH

HO

NH-C- CH3CH3 -CH

O O

OCH2 OH

HOO

NHOH

C

CH3

O

CH3 -CH

COO-

N-Acetylmuramic acid

COO-

H

HH

H

H

H

HH

H

H

The bond involved is N-glycosidic bond

Galactosamine, Glucosamine and Mannosamine act as markers in blood group

substances.

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16-36

Glycosidic linkages• Glycosidic linkages can take various forms; the

anomeric carbon of one sugar to any of the -OH

groups of another sugar to forma an - or -

glycosidic linkage

16

16-37

Disaccharides• Sucrose

• table sugar; obtained from the juice of sugar cane and sugar beet

• one unit of D-glucose and one unit of D-fructose joined by an -1,2-glycosidic bond

• nonreducing sugar: no reducing ends

Non

reducing

sugar, has

no free

group.

Bond between aldehyde and ketone group.

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16-38

Disaccharides• Lactose

• about 5% - 8% in human milk, 4% - 5% in cow’s milk

• one unit of D-galactose and one unit of D-glucose joined by a -1,4-glycosidic bond

• reducing sugar: has reducing ends

• Lactose intolerance

Lactose contains all the essential Amino Acid.

Lactose intolerance: deficiency of lactase enzyme .عدم القدرة على هضم اللاكتوز

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16-39

Disaccharides• Maltose

• two units of D-glucose joined by an -1,4-glycosidic

bond

• Resulted from hydrolysis of starch

• reducing sugar: has reducing ends

Has free

hydroxyl

group for

reaction.

Has free

hydroxyl

group for

reaction.

جذور النباتات.( ٌوجد فً α 1-1غلوكوز و الرابطة بٌنهم ) 2بتكون من Tree halose فً سكر اسمه

Lactose 16%

Glucose 70%

Sucrose (STANDARD) 100% Fructose 170%

Why Lactose is the least sweetness?

عشان ٌقدر الطفل ٌشب كمٌات اكبر من الحلٌب.

16

16-40

Disaccharides

•Cellobiose

• Two units of β-glucose linked by β-(1-4) glycosidic

bond

16

16-41

Reducing disaccharides

16

16-42

• Cellulose: the major structural component of

plants, especially wood and plant fibers

• a linear polymer of approximately 2800 D-glucose units

per molecule joined by -1,4-glycosidic bonds

• fully extended conformation with alternating 180° flips

of glucose units

• extensive intra- and intermolecular hydrogen bonding

between chains

Polysaccharides

O

OHHO

O OO

OH

HOO

O

OH

HO

HO- CH2

HO- CH2HO- CH2

1

1

1

4

4

4

Repeated unit of Glucose.

اكثر مادة موجودة على سطح الكرة الارضٌة.

لٌش السللٌلوز مهم؟

The absorption of lipid و عشان ٌمنع Intestinal reflex عشان ٌزٌد ال

ولٌس للانسان السللٌلوز لا ٌهضم لأنه طعام للحٌوانات

16

16-43

Starch• A polymers of -D-glucose units and used for

energy storage in plants, 2 forms

• amylose: continuous, helical unbranched chains of up

to 4000 -D-glucose units joined by -1,4-glycosidic

bonds

• amylopectin: a highly branched helical polymer

consisting of 24-30 units of D-glucose joined by

_1,4-glycosidic bonds and branches created by

-1,6-glycosidic bonds

• amylases catalyze hydrolysis of -1,4-glycosidic bonds

• debranching enzymes catalyze the hydrolysis of

-1,6-glycosidic bonds

16

16-44

Starch

Branch Chain

Straight Chain

16

16-45

PolysaccharidesBranching in amylopectin and glycogen

Glycogen: storage of Glucose.

16

16-46

Polysaccharides• Chitin: the major structural component of the

exoskeletons of invertebrates, such as insects

and crustaceans; also occurs in cell walls of

algae, fungi, and yeasts

• composed of units of N-acetyl--D-glucosamine joined

by -1,4-glycosidic bonds

(insert bottom of Fig 13.23)

16

16-47

16

16-48

Polysaccharides• Bacterial cell walls: prokaryotic cell walls are

constructed on the framework of the repeating

unit NAM-NAG joined by -1,4-glycosidic bonds

16

16-49

Bacterial Cell Walls• The N-acetyl-D-glucoseamine and

N-acetylmuramic acid polysaccharide is in turn

cross-linked by small peptides

• in Staphylococcus aureus, the cross link is a

tetrapeptide

• this tetrapeptide is unusual in that it contains two

amino acids of the D-series, namely D-Ala and D-Gln

• each tetrapeptide is cross linked to an adjacent

tetrapeptide by a pentapeptide of five glycine units

• Peptidoglycan is the resulted cross linking of

polysaccharides by peptides

16

16-50

Bacterial Cell Walls

16

16-51

Bacterial Cell WallsThe peptidoglycan of a bacterial cell wall

Staphylococcus

aureus

16

16-52

Polysaccharides• Glycosaminoglycans: polysaccharides based on

a repeating disaccharide where one of the

monomers is an amino sugar and the other has a

negative charge due to acid such as a sulfate or

carboxylate group

• heparin: natural anticoagulant

• hyaluronic acid: a component of the vitreous humor of

the eye and the lubricating fluid of joints

• chondroitin sulfate and keratan sulfate: components of

connective tissue

16

16-53

Heparin

The repeating unit of heparin

16

16-54

Hyaluronic AcidThe repeating unit of hyaluronic acid

16

16-55

Chondroitin sulfate

The repeating unit of chondroitin sulfate

16

16-56

Glycoproteins• Glycoproteins contain carbohydrate units

covalently bonded to a polypeptide chain

• antibodies are glycoproteins

• carbohydrates play a role as

antigenic determinants, the portions

of the antigenic molecule that

antibodies recognize and to which

they bond.

16

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Blood Group Substances• Membranes of animal plasma cells have large

numbers of relatively small carbohydrates bound

to them:

• these membrane-bound carbohydrates act as antigenic

determinants

• among the first antigenic determinants discovered

were the blood group substances

• in the ABO system, individuals are classified according

to four blood types: A, B, AB, and O

• at the cellular level, the biochemical basis for this

classification is a group of relatively small membrane-

bound carbohydrates

16

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ABO Blood Classification

16

16-59

ABO Blood Classification• in type A, the nonreducing end is NAGal

• in type B it is Gal

• in type AB, both types are present

• in Type O, neither of these terminal residues is present

Type A has N-Acetylgalactosamine

Type B has Galactosamine

Type AB has both

Type O doesn`t have

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End

Chapter 16