Chemistry of Carbohydrates

Chemistry of Carbohydrates• Definition of carbohydrates:Definition of carbohydrates:• First Definition (Old definition)First Definition (Old definition): : • Carbohydrates are substances containing Carbohydrates are substances containing

carbon, hydrogen and oxygen having the carbon, hydrogen and oxygen having the general formula general formula CnH2nOnCnH2nOn..

• (C3 H6 O3)(C3 H6 O3)

• Hydrogen and oxygen are present in 1:2 ratio Hydrogen and oxygen are present in 1:2 ratio the same ratio as water, so the French called the same ratio as water, so the French called them “Hydrates de Carbon”, i.e., carbo-them “Hydrates de Carbon”, i.e., carbo-hydrates Cn(H2O)n. hydrates Cn(H2O)n.

H3C CH COOH

OH

• The old definition is inaccurate The old definition is inaccurate becausebecause::

• There are substances which are not There are substances which are not carbohydrates but have the formula carbohydrates but have the formula CnH2nOn , e.g., CnH2nOn , e.g., acetic acid acetic acid CH3COOH (C2H4O2) and lactic CH3COOH (C2H4O2) and lactic acid.acid.

• There are some carbohydrates, There are some carbohydrates, which do not have this general which do not have this general formula, e.g., formula, e.g., amino sugars and amino sugars and deoxy sugarsdeoxy sugars

• Second Definition (new definition):Second Definition (new definition): Carbohydrates are aldehyde (CHO) Carbohydrates are aldehyde (CHO) or ketone (C=O) derivatives of or ketone (C=O) derivatives of polyhydric alcohols polyhydric alcohols (have more (have more than one OH group)than one OH group) or compounds or compounds which yield these derivatives on which yield these derivatives on hydrolysis.hydrolysis.

• Importance of carbohydrates:Importance of carbohydrates:

1.1. The chief source of energy.The chief source of energy.

2.2. Important structural components in Important structural components in animal and plant cells.animal and plant cells.

3.3. Important part of nucleic acids and Important part of nucleic acids and free nucleotides and coenzymes.free nucleotides and coenzymes.

4.4. Major antigens are carbohydrates in Major antigens are carbohydrates in nature, e.g., blood group substance.nature, e.g., blood group substance.

5.5. Biological role as a part of hormones Biological role as a part of hormones and their receptors and enzymes.and their receptors and enzymes.

• Classification of carbohydratesClassification of carbohydrates• According to the number of sugar units in the According to the number of sugar units in the

molecule there are three type:molecule there are three type:• Monosaccharides (simple sugarsMonosaccharides (simple sugars): ): They They

contain one sugar unit, i.e., and the simplest contain one sugar unit, i.e., and the simplest form of sugars and cannot be further form of sugars and cannot be further hydrolyzed. They represent the end products hydrolyzed. They represent the end products of carbohydrate digestion in the human body.of carbohydrate digestion in the human body.

• Oligosaccharides:Oligosaccharides: They contain 2 – 10 They contain 2 – 10 monosaccharide units per molecule and give monosaccharide units per molecule and give monosaccharides on acid hydrolysis.monosaccharides on acid hydrolysis.

• Polysaccharides:Polysaccharides: They contain more than 10 They contain more than 10 monosaccharide units per molecule and give monosaccharide units per molecule and give monosaccharides on acid hydrolysis.monosaccharides on acid hydrolysis.

• MonosaccharidesMonosaccharides

• They are classified according to They are classified according to the number of carbon atoms into the number of carbon atoms into five important groups. five important groups.

• Each of these groups is subdivided Each of these groups is subdivided according to the type of functional according to the type of functional chemical group into: chemical group into: AldosesAldoses (sugars containing aldehyde (sugars containing aldehyde group) and group) and KetosesKetoses (sugars (sugars containing ketone group).containing ketone group).

• 11. Bioses. Bioses:: are monosaccharides are monosaccharides containing 2 carbon atoms, containing 2 carbon atoms,

CHO

CH 2OH Glycolaldehyde

• 2. Trioses2. Trioses:: are monosaccharides are monosaccharides containing 3 carbon atoms, e.g.,containing 3 carbon atoms, e.g.,

• A- A- Aldotriose:Aldotriose: Example is Example is

CHO

C OHH

CH 2OH

C H

O

GlyceraldehydeC OH

H

H

• B- B- Ketotriose:Ketotriose: e.g.,e.g.,

• Dihydroxyacetone, the hydroxylated Dihydroxyacetone, the hydroxylated form of Acetoneform of Acetone

CH 2OH

C = O

CH 2OH

CH 3

C = O

CH 3

• 3. Tetroses:3. Tetroses: are monosaccharides are monosaccharides containing 4 carbon atoms:containing 4 carbon atoms:

• AldotetrosesAldotetroses:

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

CHO

C OHH

C OHH

CH 2OH

CHO

C HHO

C HHO

CH 2OH

CHO

C HHO

C OHH

CH 2OH

CHO

C OHH

C HHO

CH 2OH

• B- KetotetrosesB- Ketotetroses:

CH 2OH

C = O

C OHH

CH 2OH

CH 2OH

C = O

C HHO

CH 2OH

L-ErythruloseD-Erythrulose

• 4. Pentoses:4. Pentoses: they contain 5 carbon they contain 5 carbon atoms. Ribose is the most atoms. Ribose is the most important pentose because it important pentose because it enters in the structure of DNA and enters in the structure of DNA and RNA and important free RNA and important free nucleotides such as ATP and nucleotides such as ATP and coenzymes coenzymes

A- Aldopentoses:

CHO

C OHH

C OHH

C OHH

CH 2OH

CHO

C HHO

C HHO

C HHO

CH 2OH

L-Ribose

CHO

C HHO

C OHH

C OHH

CH 2OH

CHO

C OHH

C HHO

C HHO

CH 2OH

L-Arabinose

CHO

C OHH

C HHO

C OHH

CH 2OH

CHO

C HHO

C OHH

C HHO

CH 2OH

L-XyloseD-XyloseD-ArabinoseD-Ribose

• B- KetopentoseB- Ketopentose:

CH 2OH

C = O

C OHH

C OHH

CH 2OH

CH 2OH

C = O

C HHO

C HHO

CH 2OH

L-Ribulose

CH 2OH

C = O

C HHO

C OHH

CH 2OH

CH 2OH

C = O

C OHH

C HHO

CH 2OH

L-XyluloseD-XyluloseD-Ribulose

• 5.Hexoses:5.Hexoses: are monosaccharides are monosaccharides containing 6 carbon atoms. containing 6 carbon atoms.

• They are the most important They are the most important monosaccharides particularly monosaccharides particularly glucoseglucose:

• A- Adohexoses:A- Adohexoses:

CHO

C OHH

C HHO

C OHH

C OHH

CH 2OH

CHO

C HHO

C OHH

C HHO

C HHO

CH 2OH

L-Glucose

CHO

C HHO

C HHO

C OHH

C OHH

CH 2OH

CHO

C OHH

C OHH

C HHO

C HHO

CH 2OH

L-Mannose

CHO

C OHH

C HHO

C HHO

C OHH

CH 2OH

CHO

C HHO

C OHH

C OHH

C HHO

CH 2OH

L-GalactoseD-MannoseD-Glucose D-Galactose

• B- KetohexosesB- Ketohexoses:

CH 2OH

C = OC HHO

C OHH

C OHH

CH 2OH

CH 2OH

C = OC OHH

C HHO

C HHO

CH 2OH L-FructoseD-Fructose

Asymmetric carbon atomAsymmetric carbon atom

- Asymmetric carbon atom is Asymmetric carbon atom is the carbon atom attached to the carbon atom attached to which 4 different groups or which 4 different groups or

atoms.atoms.

• Ordinary light vibrates in all Ordinary light vibrates in all directions. directions.

• Ordinary light can be changed to Ordinary light can be changed to plane polarized light by passing it plane polarized light by passing it through a prism made of calcium through a prism made of calcium carbonate .carbonate .

• Plane polarized light vibrates in Plane polarized light vibrates in one plane and direction. one plane and direction.

• Optical activity is determined by polariscope Optical activity is determined by polariscope oror polarimeter that is polarimeter that is consisted of:consisted of:

• A light source (usually a sodium lamp). A light source (usually a sodium lamp). • A polarizer that is a prism made of calcite. A polarizer that is a prism made of calcite. • A narrow slit path to bring forth a parallel A narrow slit path to bring forth a parallel

beam of light. beam of light. • A polarimeter tube to contain the solution of A polarimeter tube to contain the solution of

the substance tested (mostly 1.0 decimeter in the substance tested (mostly 1.0 decimeter in lengthlength). ).

• A scale graduated in increasing positive (+) A scale graduated in increasing positive (+) degrees from 0.0 on its right part and in degrees from 0.0 on its right part and in increasing negative (-) degrees from 0.0 on increasing negative (-) degrees from 0.0 on its left part.its left part.

• Importance of asymmetric carbon Importance of asymmetric carbon atomatom: Any compound containing : Any compound containing asymmetric carbon atom has the asymmetric carbon atom has the following two properties:following two properties:

1.1. Isomerism is created around it.Isomerism is created around it.

2.2. It makes the compound optically It makes the compound optically activeactive

Optical activityOptical activity

• Definition:Definition: It is the ability of the It is the ability of the sugar to rotate the plane of the sugar to rotate the plane of the plane polarized light. plane polarized light.

• The sugar that rotates the light to The sugar that rotates the light to the right is called the right is called dextrorotatorydextrorotatory (d (d or +) such or +) such as glucose, galactose as glucose, galactose and starchand starch and that rotating light to and that rotating light to the left is called the left is called levorotatorylevorotatory (l or -) (l or -) such as such as fructose and invert sugarfructose and invert sugar..

• Factors affecting optical activity:Factors affecting optical activity:

1.1. Type and Concentration of the Type and Concentration of the substance and type of solvent. substance and type of solvent.

2.2. Type of light used and temperatureType of light used and temperature..

3.3. Length of polarimeter tube in Length of polarimeter tube in decimeters.decimeters.

Specific rotation: • It is the observed angle of deviation of the It is the observed angle of deviation of the

plane polarized light in degrees from the plane polarized light in degrees from the straight path. straight path.

• It is measured when the solution of the It is measured when the solution of the substance or the sugar dissolved in water is substance or the sugar dissolved in water is introduced in the path of the plane polarized introduced in the path of the plane polarized light under the following conditions. light under the following conditions.

• The light source used is sodium light, the The light source used is sodium light, the temperature is 20oC, the concentration is temperature is 20oC, the concentration is 100 gm/ 100 mL and the polarimeter tube is 100 gm/ 100 mL and the polarimeter tube is one decimeter in length.one decimeter in length.

• Each optically active substance Each optically active substance has a characteristic specific has a characteristic specific rotation such as, rotation such as, -glucose is -glucose is +112, +112, -glucose is +19 and fructose -glucose is +19 and fructose is - 92.5.is - 92.5.

• Uses of polariscope and importance of optical Uses of polariscope and importance of optical activity:activity:

1.1. Identify an unknown optically active substance.Identify an unknown optically active substance.2.2. Identify whether the substance is optically Identify whether the substance is optically

active or not.active or not.3.3. Identify whether the substance is levorotatory Identify whether the substance is levorotatory

or dextrorotatory.or dextrorotatory.4.4. Determine the concentration of the substance.Determine the concentration of the substance.5.5. Differentiate between glucosuria and Differentiate between glucosuria and

lactosuria. This is important in late pregnancy lactosuria. This is important in late pregnancy to differentiate between diabetes mellitus to differentiate between diabetes mellitus (glucose) and the normal appearance of lactose (glucose) and the normal appearance of lactose produced by the mammary glands in urine.produced by the mammary glands in urine.

Mutarotation:

• It is a temporary change in the It is a temporary change in the specific rotation of the sugar when it specific rotation of the sugar when it is freshly prepared. is freshly prepared.

• Mutarotation is due to the presence Mutarotation is due to the presence of a free anomeric carbon (C1 in of a free anomeric carbon (C1 in aldoses, C2 in ketoses).aldoses, C2 in ketoses).

• For example, For example, -glucose when freshly -glucose when freshly prepared has a specific rotation of prepared has a specific rotation of +112, then the specific rotation +112, then the specific rotation decreases gradually till it stabilizes decreases gradually till it stabilizes at +52.5 (point of equilibrium)at +52.5 (point of equilibrium)

-glucose when freshly prepared has -glucose when freshly prepared has a specific rotation of +19, then the a specific rotation of +19, then the specific rotation gradually increases specific rotation gradually increases till it is stabilizes at +52.5 (point of till it is stabilizes at +52.5 (point of equilibrium)equilibrium)

• In solution, In solution, -glucose changes to -glucose changes to -glucose through the straight -glucose through the straight chain form and vice versa till the chain form and vice versa till the point of equilibrium is reached, point of equilibrium is reached, where the solution is composed of: where the solution is composed of: 2/3 2/3 -glucopyranose, 1/3 -glucopyranose, 1/3 --glucopyranose, 1% glucopyranose, 1% -glucose (-glucose ( and and -glucofuranose) and 0.0025% -glucofuranose) and 0.0025% open chain form (Reactive form).open chain form (Reactive form).

• Cyclic structure of monosaccharides

CH O

C OH

C HHOC OHHC OHH

CH 2OH

-D-glucopyranose

OH

OH

H

OHH

OHH

OH

CH 2OH

H1

23

4

5

6

H OH

OH

OH

HH

OHH

OH

CH 2OH

H1

23

4

5

6

-D-glucopyranoseD-glucose

• Steps of the cyclic form construction:Steps of the cyclic form construction:1.1. Condensation of a molecule of H2O Condensation of a molecule of H2O

with the aldehyde or keto group of the with the aldehyde or keto group of the sugar to form aldenol or ketonol sugar to form aldenol or ketonol group.group.

2.2. The OH group from the aldenol group The OH group from the aldenol group condenses with the OH on C4 condenses with the OH on C4 (Furanose) or C5 (Pyranose) of the (Furanose) or C5 (Pyranose) of the aldo-sugar to forms a ring or hemi-aldo-sugar to forms a ring or hemi-acetal structure with the liberation of acetal structure with the liberation of H2O again. Keto-sugar condenses H2O again. Keto-sugar condenses only with C5 (Furanose) or with C6 only with C5 (Furanose) or with C6 (Pyranose).(Pyranose).

• When the remaining OH on the When the remaining OH on the aldehyde or the keto carbon atom in aldehyde or the keto carbon atom in the cyclic form is located on the right the cyclic form is located on the right side, the sugar form is called side, the sugar form is called -sugar -sugar and if it is located on the left side the and if it is located on the left side the sugar is called sugar is called -sugar.-sugar.

CHO

C OHH

C HHO

C OHH

C OHH

CH 2OH

+ H2O

C

C OHH

C HHO

C OHH

C OHH

CH 2OH

HOHHO

+ H2O

C

C OHH

C HHO

CH

C OHH

CH 2OH

HOH

C

C OHH

C HHO

C OHH

CH

CH 2OH

HOH

O

(or) -D-Gluco furanose

HO

HO

O

Furan ring

O

Pyran ring

OR

(or) -D-Gluco pyranose

D-Glucose D-Glucose aldenol,unstable

O

CH 2OH

C = O

C HHO

C OHH

C OHH

CH 2OH

+ H2O

CH 2OH

C OHHO

C HHO

C OHH

C OHH

CH 2OH

+ H2O

CH 2OH

C OH

C HHO

C OHH

CH

CH 2OH

O

CH 2OH

C OH

C HHO

C OHH

C OHH

H2C O

(or) -D-Fructofu ranose

O

Furan ring

O

Pyran ring

OR

(or) -D-Fructopyr anose

D-Fructose D-Fructose ketonol,unstable

HO

HO

• Haworth's projection formulaHaworth's projection formula::• Because Fisher’s formula could not explain some Because Fisher’s formula could not explain some

of the chemical and physical characteristics of of the chemical and physical characteristics of sugars, Haworth put forth his projection formula.sugars, Haworth put forth his projection formula.

• C and O atoms of the ring are drawn in the plane C and O atoms of the ring are drawn in the plane of the page.of the page.

• H and OH or other side groups are written on H and OH or other side groups are written on perpendicular plane.perpendicular plane.

• All groups located on the left side of fisher’s are All groups located on the left side of fisher’s are written upwards. All groups located on the right written upwards. All groups located on the right side of fisher’s are written downwardsside of fisher’s are written downwards..

• The radical of the molecule (the extra-cyclic part) The radical of the molecule (the extra-cyclic part) is written upwards in D sugar and inside the ring is written upwards in D sugar and inside the ring (or down wards) in L-sugar. (or down wards) in L-sugar.

OH

H

H

CHO H

H OH

OH H

O

C

C OHH

C HHO

CH

C OHH

CH 2OH

H OH

O

CH 2OH

H

OH

H

CHO H

H OH

OH H

O

C

C OHH

C HHO

CH

C OHH

CH 2OH

HO H

O

CH 2OH

123

4

-D-glucofuranose

5

6

123

4

-D-glucofuranose

5

6

C

C OHH

C HHO

C OHH

CH

CH 2OH

HO H

OH

OH

OH

HH

OHH

OH

CH 2OH

H

O

-D-glucopyranose

C

C OHH

C HHO

C OHH

CH

CH 2OH

H OH

OH

OH

H

OHH

OHH

OH

CH 2OH

H

O

-D-glucopyranose

OH

CH 2OH

H

CH 2OH

OH H

H OH

O

CH 2OH

C OH

C HHO

C OHH

CH

CH 2OH

1

2

34

-D-fructofuranose

5

6

O

CH 2OH

C OH

C HHO

C OHH

C OHH

CH 2

-D-fructopyranoseO

OH

OH

CH 2OH

OHOH

HOH

H

H

H 1

2

34

5

6

Isomerism

• Isomers are substances which have Isomers are substances which have the same molecular formula but differ the same molecular formula but differ in distribution of their atoms into in distribution of their atoms into groups or distribution of these groups groups or distribution of these groups and atoms in the space around carbon and atoms in the space around carbon atoms. There are 2 types of atoms. There are 2 types of isomerism;isomerism;

1.1. Structural isomerism. Structural isomerism.

2.2. Stereo-isomerismStereo-isomerism.

1. Structural isomerism:

• They are isomers that have different They are isomers that have different structure due to different ways of structure due to different ways of arrangement of atoms and groups arrangement of atoms and groups forming the molecule. Types of forming the molecule. Types of structural isomerism are four as structural isomerism are four as follows:follows:

• a. Chain isomerism.a. Chain isomerism.

• These are isomers that have different These are isomers that have different structures due to different ways of structures due to different ways of attachment of carbon atoms forming attachment of carbon atoms forming the molecule, the molecule,

CH2 CH2 CH2 CH3H3C CH2 CH CH3H3C

CH3

H3C C CH3

CH3

CH3

Neo-PentaneN-pentane Iso-Pentane

• b. Positional isomerism:b. Positional isomerism:

• These are isomers that have the same These are isomers that have the same carbon skeleton but differ in the carbon skeleton but differ in the position of the substituent groups, e.g.,position of the substituent groups, e.g.,

CH 3 CH 2 CH 3 H3C CH 2 CH 2

Cl

H3C CH CH 3

Clpropane n-Propyl chloride Iso-Propyl chloride

OH

OH

H

OHH

OHH

OH

CH 2OH

H

Glucose-1-phosphate

OH

OH

H

OH

H

OHH

OH

CH 2O-P=O

H

OH

OH

H

O - P = O

H

OHH

OH

CH 2OH

H

OH

OH

-D-Glucose Glucose-6-phosphate

OH

OH

C.Functional group isomerismFunctional group isomerism::

• - These are isomers that have the same - These are isomers that have the same carbon skeleton, the same position of carbon skeleton, the same position of substituent group but have different substituent group but have different functional group (aldo-/keto-). functional group (aldo-/keto-).

c

Aldehydes such as;Glyceraldehyde,

Erythrose,Ribose, Xylose

Glucose

Ketones such as;Dihydroxyacetone,

Erythrulose,Ribulose, Xylulose,

Fructose

d. Ring isomerism:

• Pyran/furan forms such as Pyran/furan forms such as glucopyranose and glucofuranose, and glucopyranose and glucofuranose, and fructopyranose and fructofuranose.fructopyranose and fructofuranose.

OH

CH 2OH

H

CH 2OH

OH H

H OH

O

CH 2OH

C OH

C HHO

C OHH

CH

CH 2OH

1

2

34

-D-fructofuranose

5

6

O

CH 2OH

C OH

C HHO

C OHH

C OHH

CH 2

-D-fructopyranoseO

OH

OH

CH 2OH

OHOH

HOH

H

H

H 1

2

34

5

6

2. Stereo-isomerism:

• They are molecules having the same structure but differ in position of their different groups and atoms in the space,

• The number of stereoisomers = 2n, where n is the number of asymmetric carbon atoms. There are four types of stereo-isomerism as follows:

a. D and L isomerism • They differ in distribution of H and OH They differ in distribution of H and OH

groups around the sub-terminal groups around the sub-terminal asymmetric carbon atoms. asymmetric carbon atoms.

• D form has the OH group to the right of D form has the OH group to the right of the sub-terminal carbon atom .whereas, the sub-terminal carbon atom .whereas, it is on the left in L form.it is on the left in L form.

• This difference make the two forms (D This difference make the two forms (D and L) mirror image to each other due and L) mirror image to each other due to the change of the position of all H to the change of the position of all H and OH groups into the opposite and OH groups into the opposite direction of D form in L form. direction of D form in L form.

CHO

C OHH

CH 2OH

CHO

CHO H

CH 2OH

D-GlyceraldehydeOH group on sub-terminal

carbon is written on right side.OH group on sub-terminal

carbon is written on left side.

L-Glyceraldehyde

b. Epimers:• They are stereoisomers which differ in They are stereoisomers which differ in

distribution of H and OH groups around distribution of H and OH groups around a single asymmetric carbon atom other a single asymmetric carbon atom other than the anomeric and DL-form than the anomeric and DL-form creating carbon before the last i.e., creating carbon before the last i.e., without difference on other carbon without difference on other carbon atoms. atoms.

• Ribose is an epimer to each of Ribose is an epimer to each of arabinose and xylose. Glucose is an arabinose and xylose. Glucose is an epimer to each of mannose and epimer to each of mannose and galactosegalactose.

Chemistry of carbohydrates

• DR : Yakout

• Uploaded by : Mohamed Hassan

CHO

C OHH

C OHH

C OHH

CH 2OH

CHO

C HHO

C OHH

C OHH

CH 2OH

CHO

C OHH

C HHO

C OHH

CH 2OH

XyloseRibose Arabinose

CHO

C OHH

C HHO

C OHH

C OHH

CH 2OH

CHO

C HHO

C HHO

C OHH

C OHH

CH 2OH

CHO

C OHH

C HHO

C HHO

C OHH

CH 2OH

GalactoseGlucose Mannose

• Arabinose and xylose as well as galactose and mannose are not epimers to each other

• because they differ around distribution of H and OH in more than one asymmetric center.

c. Anomers:

• They are stereoisomers which differ in distribution of H and OH group around the asymmetric anomeric carbon atom C1 in aldoses or C2 in ketoses after cyclization of the molecule, e.g.

OH

OH

H

OHH

OHH

OH

CH 2OH

H

-D-Glucose

OH

OH

OH

HH

OHH

OH

CH 2OH

H

-D-Glucose

d. Geometric isomerism:

• It involves distribution of atoms or groups around the axis of a double bond in the space.

C

C

HOOC

HOOC

H

H

C

C

HOOC

H

H

COO H

Fumaric acid(trans form)

Maleic acid(cis form)

• Physical Properties of Monosaccharides:

• All monosaccharides are soluble in water.

• All monosaccharide show the property of optical activity.

• All monosaccharides can exist in α and β forms.

• All monosaccharides undergo mutarotation.

Sugar derivatives

1. Sugar acids

2. Sugar alcohols

3. Amino sugars

4. Deoxy sugars

1.Sugar acids

1.1. Produced by oxidation of Produced by oxidation of carbonyl carbon to carboxylic carbonyl carbon to carboxylic group.group.

2.2. Or by oxidation of last hydroxy Or by oxidation of last hydroxy carbon to carboxylic group.carbon to carboxylic group.

3.3. Or by oxidation of both.Or by oxidation of both.

1.Aldonic1.Aldonic

CHO

C OHH

C HHO

C OHH

C OHH

CH 2OH

COOH

C OHH

C HHO

C OHH

C OHH

CH 2OH

bromine water, O2

D-Gluconic acidD-Glucose

2-Uronic2-Uronic

CHO

C OHH

C HHO

C OHH

C OHH

CH 2OH

CHO

C OHH

C HHO

C OHH

C OHH

COOH

Dil. Nitric acid

D-Glucuronic acidD-Glucose

H2O2

3-Aldaric3-Aldaric

CHO

C OHH

C HHO

C OHH

C OHH

CH 2OH

COOH

C OHH

C HHO

C OHH

C OHH

COOH

Conc. Nitric acid

D-Glucaric acidD-Glucose

O2

2-sugar alcohols:2-sugar alcohols:

• Reduction of monosaccharides gives sugar alcohols.

CH O

C

CH 2OH

H2

Na amalgum, H2SO4

Sugar alcohol

OHH

n

CH 2OH

C

CH 2OH

OHH

n

Monosaccharide

• Ribose reduction Ribose reduction gives gives RibitolRibitol that is a part that is a part of the structure of vitamin B2 of the structure of vitamin B2

(Riboflavin),(Riboflavin),

CHO

C

C OHH

C OHH

CH 2OH

H2

Na amalgum, H2SO4

Ribitol

CH 2OH

C OHH

C OHH

C OHH

CH 2OH

OHH

Ribose

• Reduction of glucoseReduction of glucose gives sorbitol or gives sorbitol or glucitol that enters in medical glucitol that enters in medical industriesindustries

CHO

C

C HHO

C OHH

C OHH

CH 2OH

H2

Na amalgum, H2SO4

Sorbitol

CH 2OH

C OHH

C HHO

C OHH

C OHH

CH 2OH

OHH

Glucose

• Fructose reductionFructose reduction gives Sorbitol or gives Sorbitol or Mannitol. Mannitol.

CH2OH

C = O

C HHO

C OHH

C OHH

CH2OH

CH2OH

C OHH

C HHO

C OHH

C OHH

CH2OH

H2

Na amalgum, H2SO4

Mannitol

CH2OH

C HHO

C HHO

C OHH

C OHH

CH2OH

OR

Fructose Sorbitol

• Inositol:Inositol: It is a hexahydric alcohol (6 OH It is a hexahydric alcohol (6 OH groups),groups),

H

OH

OH

HH

OHH

OH

OHOH

H H1

23

4

5 6

Inositol

- It presents in high concentration in heart and muscles tissues, so it is called muscle sugar

3-Amino sugars :• Replacing OH group on C2 by an

amino group (NH2) produces them.

OH

OH

H

OHH

NH2H

OH

CH 2OH

H

-D-glucoamine

2

N-acetyl-glucosamine sulfated glucosamine

OH

OH

H

OHH

HNH

OH

CH 2OH

H

2

C CH 3

O

OH

OH

H

OHH

NH-SO3HH

OH

CH 2O-SO3H

H

2

6

OOH

H

H

OHH

NH2H

OH

CH2OH

H

2

OOH

H

H

OHH

HNH

OH

CH2OH

H

2

C CH3

O- D-galactosamine N- acetyl-galactosamine sulfated N-acetyl- galactosamine

OO-SO3H

H

H

OHH

HNH

OH

CH2O - SO 3H

H

2

C CH3

O

4

6

4-Deoxysugars:4-Deoxysugars:• These are sugars in which OH group is These are sugars in which OH group is

replaced by H.replaced by H.

• 1. At C21. At C2 gives Deoxy sugar proper gives Deoxy sugar proper

deoxyribose that enters in structure ofdeoxyribose that enters in structure of DNA.,DNA.,

CHO

C OHH

C OHH

C OHH

CH 2OH

CHO

C HH

C OHH

C OHH

CH 2OH

Ribose Deoxyribose

2. 2. At C6At C6 gives methyl pentoses gives methyl pentoses (Methylose), e.g., L-galactose gives L-(Methylose), e.g., L-galactose gives L-fucose and, L-Mannose gives L-fucose and, L-Mannose gives L-rhamnose,rhamnose,

CHO

C HHO

C OHH

C OHH

C HHO

CH2OH

CHO

C HHO

C OHH

C OHH

C HHO

CH3

L-fucose

CHO

C OHH

C OHH

C HHO

C HHO

CH2OH

CHO

C OHH

C OHH

C HHO

C HHO

CH3

L-RhamnoseL-galactose L-Mannose

Glycosides • They are products of the reaction of the They are products of the reaction of the

OH group of the anomeric carbon with OH group of the anomeric carbon with either another OH group or NH2 group either another OH group or NH2 group from another compound producing from another compound producing compounds called glycosides.compounds called glycosides.

• The other compounds may be another The other compounds may be another sugar,sugar, called called glycan glycan or a or a non-sugarnon-sugar, , called called aglycan.aglycan. The glycosides can be The glycosides can be named according to the type of sugar, named according to the type of sugar, e.g., glucose forms glucosides and e.g., glucose forms glucosides and galactose forms galactosides, …etc.galactose forms galactosides, …etc.

• Types of Glycosides:Types of Glycosides:

• I. Glycosides containing R–O–R (ether I. Glycosides containing R–O–R (ether linkage):linkage):

• Disaccharides: e.g., lactose and Disaccharides: e.g., lactose and maltose see later. maltose see later.

• II. R-N-R Glycosides:II. R-N-R Glycosides:

• Nucleotides: The sugar is ribose or Nucleotides: The sugar is ribose or deoxyribose linked with purine and deoxyribose linked with purine and pyrimidine bases. pyrimidine bases.

• Glycoproteins.Glycoproteins.

OH

OH

H

OHH

OHH

OH

CH2OH

H14

H2OCH3OH

-D-Glucose

Methylalcohol

OH

OH

H

O-CH3H

OHH

OH

CH2OH

H14

-Methyl-glucoside

OH

OH

O-CH3

HH

OHH

OH

CH2OH

H14

-Methyl-glucoside

OR

Oligosaccharides

• Disaccharides:Disaccharides:

• 1- Reducing Disaccharides1- Reducing Disaccharides

• It has a free aldehyde group (anomeric It has a free aldehyde group (anomeric carbon) carbon)

• 2- Non-reducing Disaccharides:2- Non-reducing Disaccharides:

• It has no free aldehyde group It has no free aldehyde group (anomeric carbon) (anomeric carbon)

1- Reducing Disaccharides:Reducing Disaccharides:

A-Maltose (malt sugar):A-Maltose (malt sugar):

It consists of 2 It consists of 2 -glucose units linked by -glucose units linked by -1,4-glucosidic linkage, -1,4-glucosidic linkage,

OH

OH

H

H

OHH

OH

CH 2OH

H

OH OH ..... H

H ..... OHH

OHH

OH

CH 2OH

H

O

and Maltose-Glucose Glucose

1 4

It has a free aldehyde group (anomeric It has a free aldehyde group (anomeric carbon), therefore it :carbon), therefore it :

1.1. exists in exists in and and forms. forms. 2.2. exhibits mutarotation.exhibits mutarotation.3.3. is a reducing disaccharide. is a reducing disaccharide. 4.4. gives osazone called maltosazone gives osazone called maltosazone

(Rosette shaped).(Rosette shaped).5.5. is a fermentable sugar, due to is a fermentable sugar, due to --

glucosidic bond.glucosidic bond.It is produced during digestion of starch.It is produced during digestion of starch. It is hydrolyzed by acids and in human It is hydrolyzed by acids and in human

intestine by maltase enzyme.intestine by maltase enzyme.

B-Isomaltose:B-Isomaltose:

It is formed of 2 It is formed of 2 -glucose linked by -glucose linked by --1,6-glucosidic linkage.1,6-glucosidic linkage.

OH

OH

H

O

H

OHH

OH

CH 2OH

H

and isomaltose

-Glucose

Glucose

1

6O

H

OH

OH ..... H

H ..... OHH

OHH

OH

CH 2

H

C-Lactose:C-Lactose:

It is formed of It is formed of -galactose and -galactose and -glucose -glucose linked by linked by -1,4-glucosidic linkage -1,4-glucosidic linkage

OOH

H HH

OHH

OH

CH 2OH

H

OH OH ..... H

H ..... OHH

OHH

OH

CH 2OH

H

and Lactose-Galactose Glucose

1 4O

• It is the milk sugar with free aldehyde It is the milk sugar with free aldehyde making it a reducing disaccharide.making it a reducing disaccharide.

• lactosazone forming (Puff-like), and lactosazone forming (Puff-like), and having having and and -forms. -forms.

• It is digestible by lactase into It is digestible by lactase into glucose and galactose.glucose and galactose.

• It is excreted in urine of pregnant It is excreted in urine of pregnant and lactating femalesand lactating females

• It is the most suitable sugar for baby feeding It is the most suitable sugar for baby feeding as a sweetener for milk because:as a sweetener for milk because:

1.1. It is the least sweet sugar so that the baby can It is the least sweet sugar so that the baby can nurse a large amount of mother’s milk without nurse a large amount of mother’s milk without getting his appetite lost. getting his appetite lost.

2.2. Because it has a Because it has a -glycosidic linkage it is non--glycosidic linkage it is non-fermentable sugar, so it does not form gases fermentable sugar, so it does not form gases and not cause colic to the infant.and not cause colic to the infant.

3.3. It has a laxative effect and prevents It has a laxative effect and prevents constipation and non-irritant to the stomach constipation and non-irritant to the stomach and does not induce vomiting.and does not induce vomiting.

4.4. Unabsorbed sugar is used as a food for large Unabsorbed sugar is used as a food for large intestinal bacteria that form a number of intestinal bacteria that form a number of vitamins that benefits the baby.vitamins that benefits the baby.

D) CellobioseD) Cellobiose::• It is formed of 2 It is formed of 2 -glucose units linked -glucose units linked

by by -1,4-glucosidic linkage.-1,4-glucosidic linkage.

• Reducing disaccharide. Reducing disaccharide.

• It is the building unit of cellulose. It is the building unit of cellulose.

• It is non-fermentable, indigestible.It is non-fermentable, indigestible.

• shows mutarotation .shows mutarotation .

• have have and and -forms. -forms.

OH

OH HH

OHH

OH

CH 2OH

H

OH OH

HH

OHH

OH

CH 2OH

H1 4O

Cellobiose-Glucose -Glucose

2. Non-reducing Disaccharides:

A. SucroseA. Sucrose: OH

OH

H

H

OHH

OH

CH 2OH

H 1

Sucrose

-Glucose

-Fructose

CH 2OH

O

H

CH 2OH

OH H

H OH

O

2

• It is table sugar and sugar of cane and It is table sugar and sugar of cane and molasses and is formed of molasses and is formed of -glucose -glucose linked to linked to -fructose by -fructose by ---1,2-linkage. It -1,2-linkage. It is a fermentable sugar.is a fermentable sugar.

• The 2 anomeric carbons (C1 of glucose The 2 anomeric carbons (C1 of glucose and C2 of fructose) are involved in the and C2 of fructose) are involved in the linkagelinkage(no free groups)(no free groups) so it is: so it is:

• Non-reducing sugar. Non-reducing sugar.

• Non osazone forming.Non osazone forming.

• Not mutarotating. Not mutarotating.

• Not having Not having or or -forms.-forms.

• It is a dextrorotatory sugar but when It is a dextrorotatory sugar but when it is hydrolyzed by sucrase enzyme it is hydrolyzed by sucrase enzyme or by acid hydrolysis (HCl) the or by acid hydrolysis (HCl) the mixture of sugars produced is mixture of sugars produced is levorotatory.levorotatory.

• This is because the levorotatory This is because the levorotatory power of fructose (-92.5) power of fructose (-92.5) cancelscancels the the dextrorotatory power of glucose dextrorotatory power of glucose (+52.5) since they are at equal (+52.5) since they are at equal proportions in the product. This is proportions in the product. This is why this sugar is called why this sugar is called invert sugarinvert sugar..

• Sucrase enzyme is therefore, also Sucrase enzyme is therefore, also called called invertaseinvertase enzyme enzyme.

Differences between sucrose and invert sugar:

Sucrose Invert sugar

Formed of: -glucose and -fructose linked by 1,2-linkage.

An equimolar mixture of free -glucose and -fructose.

Optical activity: Dextrorotatory. Levorotatory.

Reductive ability: Non-reducing (no free CHO or C=O groups).

Reducing (there are free CHO and C=O groups)

Digestion: Needs digestion (sucrase). No further digestion.

Other names: Cane and table sugar. Bees honey and invert sugar.

B. TrehaloseB. Trehalose::

It is formed of 2 It is formed of 2 -glucose units linked by -glucose units linked by -1,1-glucosidic linkage.-1,1-glucosidic linkage.

Present in a highly toxic lipid extracted Present in a highly toxic lipid extracted from Mycobacterium tuberculosis. from Mycobacterium tuberculosis.

OH

OH

H

H

OHH

OH

CH2OH

H

O

H H

OHHOH2C

H

OHH

OH H

O

11

Trehalose-Glucose -Glucose

• TrisaccharidesTrisaccharides

• Rhafinose:Rhafinose:

• Presents in molasses. It is a Presents in molasses. It is a trisaccharide formed of one unit of trisaccharide formed of one unit of each of glucose, galactose and each of glucose, galactose and fructose.fructose.

• TetrasaccharidesTetrasaccharides

• Stacchyose:Stacchyose:

• - Presents in onions. It is formed of 2 - Presents in onions. It is formed of 2 galactose units and one unit of each galactose units and one unit of each of glucose and fructose.of glucose and fructose.

Polysaccharides

• They are classified into:They are classified into:

A-HomopolysaccharidesA-Homopolysaccharides

B-HeteropolysaccharidesB-Heteropolysaccharides..

A-HomopolysaccharidesA-Homopolysaccharides

• They yield only one type of They yield only one type of monosaccharides on hydrolysis and monosaccharides on hydrolysis and they are named according to the type of they are named according to the type of that monosaccharide, e.g.,that monosaccharide, e.g.,

• Hexosans + H2O Hexosans + H2O Hexoses Hexoses

• Pentosans + H2O Pentosans + H2O Pentoses Pentoses

Hexosans:

I. GlucosansI. Glucosans::

• They produce only glucose on They produce only glucose on hydrolysis.hydrolysis.

• They include; starch, dextrins, They include; starch, dextrins, dextrans, glycogen and cellulose,dextrans, glycogen and cellulose,

A. Starch:• It is the stored form of carbohydrate of It is the stored form of carbohydrate of

plants. It never exists in animals.plants. It never exists in animals.• It is present in cereals such as wheat and It is present in cereals such as wheat and

rice and tubers such as potatoes.rice and tubers such as potatoes.• It is in the form of starch granules. The It is in the form of starch granules. The

core of the granule is amylose (20%) and core of the granule is amylose (20%) and the shell is amylopectin (80%).the shell is amylopectin (80%).

• Due to its high molecular weight it forms Due to its high molecular weight it forms colloidal solution in hot water.colloidal solution in hot water.

Starch granule

AmyloseAmylopectin

• 1. Amylose:1. Amylose:. . Straight chain compound Straight chain compound present in the form glucose units present in the form glucose units linked by linked by -1,4-glucosidic bond of a -1,4-glucosidic bond of a helix formed of a large number of helix formed of a large number of - - glucose.glucose.

OH H

H

OHH

OH

CH 2OH

H

OH H

OHH

OH

CH 2OH

H

O

Amylose

14

n

OO

1 4

It forms the inner part of starch granules

• Amylopectin:Amylopectin:• It forms the outer coat of starch It forms the outer coat of starch

granule and is insoluble in water. granule and is insoluble in water. • It is branched chains formed of a large It is branched chains formed of a large

number of number of -glucose units linked by -glucose units linked by --1,4-glucosidic linkage along the branch 1,4-glucosidic linkage along the branch and by and by -1,6-glucosidic linkage at the -1,6-glucosidic linkage at the branchingbranching pointpoint that occur every that occur every 25-3025-30 glucose units. Due to its high glucose units. Due to its high molecular weight, it forms a colloidal molecular weight, it forms a colloidal solution.solution.

• Starch can be hydrolyzed by HCl or Starch can be hydrolyzed by HCl or amylase. amylase.

OH H

H

OHH

OH

CH 2OH

H

OH H

OHH

OH

CH 2OH

H

O

Amylopectin

14O

1 4

OH H

H

OHH

OH

CH 2OH

H

OH H

OHH

OH

CH 2OH

H

O

14O

O1 4

OH H

H

OHH

OH

CH 2

H

OH H

OHH

OH

CH 2OH

H

O

14

n

O1 4

6

O

B. Dextrins:• Products of hydrolysis of starch and Products of hydrolysis of starch and

include amylodextrin, erythrodextrin, include amylodextrin, erythrodextrin, achrodextrin which form color with achrodextrin which form color with iodine iodine

• They have sweet taste. They have sweet taste.

• They are easily digested than starch as They are easily digested than starch as in corn and rice syrup.in corn and rice syrup.

C. DextranC. Dextran: : • A compound formed of A compound formed of -glucose units -glucose units

linked by linked by -1,4, -1,4, -1,3- and -1,3- and -1,6-linkage -1,6-linkage present in the form of a network that is present in the form of a network that is synthesized by certain bacteria having synthesized by certain bacteria having sucrose in its media. sucrose in its media.

It has a great biochemical importanceIt has a great biochemical importance,,1.1. It is used as plasma substitute to restore It is used as plasma substitute to restore

blood pressure in cases of shock.blood pressure in cases of shock.2.2. Iron used for treatment of iron deficiency Iron used for treatment of iron deficiency

anemia is used as dextran ferrous sulfate anemia is used as dextran ferrous sulfate intramuscular injection.intramuscular injection.

3.3. Sodium dextran sulfate is an Sodium dextran sulfate is an anticoagulant.anticoagulant.

D. GlycogenD. Glycogen::

• It is the stored form of carbohydrate in It is the stored form of carbohydrate in animal, particularly in muscles and liver. animal, particularly in muscles and liver.

• Its structure is similar to amylopectin a Its structure is similar to amylopectin a branched tree with branched tree with -1,4-glucosidic linkage -1,4-glucosidic linkage along the branch and along the branch and -1,6-glucosidic linkage -1,6-glucosidic linkage at the branching point.at the branching point.

• The glycogen tree is shorter and more The glycogen tree is shorter and more branched (a branch point branched (a branch point every 8-10every 8-10 glucose glucose units) than amylopectin.units) than amylopectin.

• It is digestible because human amylases It is digestible because human amylases hydrolyze hydrolyze -glucosidic linkage.-glucosidic linkage.

E. CelluloseE. Cellulose: : • It is a structural polysaccharide and forms It is a structural polysaccharide and forms

the skeleton of plant cells and does not the skeleton of plant cells and does not enter in animals cell structures. enter in animals cell structures.

• It is a straight chain molecule formed of a It is a straight chain molecule formed of a large number of large number of -glucose units linked by -glucose units linked by -1,4-glucosidic linkage.-1,4-glucosidic linkage.

• It is water insoluble and enters in structure It is water insoluble and enters in structure of cotton and paper of cotton and paper

• It is the major food for herbivorous animal It is the major food for herbivorous animal where it is fermented into volatile fatty where it is fermented into volatile fatty acids.acids.

• It gives cellobiose on hydrolysis with HCl.It gives cellobiose on hydrolysis with HCl.

• It is indigestible but is very essential It is indigestible but is very essential in food for:in food for:

1.1. Prevention of constipation by Prevention of constipation by increasing the bulk of stools.increasing the bulk of stools.

2.2. Its fermentation by large intestinal Its fermentation by large intestinal bacteria give volatile fatty acids that bacteria give volatile fatty acids that is anticancer for colon cells and is anticancer for colon cells and gives also some water soluble gives also some water soluble vitamins.vitamins.

3.3. It adsorbs toxins present in foods It adsorbs toxins present in foods and prevents its absorption into the and prevents its absorption into the body.body.

Starch Glycogen Cellulose

1.Nature: Stored form of carbohydrate in plants.

Stored form ofcarbohydrates in animals.

Structural form of carbohydrate in plant cells but prevents

constipation in human.

1.Source: Cereals, e.g., wheat, rice, and tubers, e.g.,

potatoes.

Muscles and liver Linen and cotton are nearly pure cellulose.

1.Solubility: Amylose is water soluble and amylopectin is

insoluble.

Water soluble forming colloidal solution.

Water insoluble.

1.Nature of the chains:Amylose is helical straight chain (-glucose

units linked by -1,4-glucosidic bonds). Amylopectin is branched chain (-glucose units linked by -1,4- and -1,6-glucosidic

bonds).

Branched chain similar to amylopectin but its

trees are shorter and have more branches

than amylopectin tree.

Straight chain (large number of -glucose units linked by -

1,4- glucosidic bonds).

1.Reaction with iodine:Amylose gives blue color and amylopectin

gives red color.

Gives red color. No color.

1.Digestibility: Is hydrolyzed by HCl or amylase into dextrins

and maltose.

Digestible by amylase into dextrins and maltose.

Non-digestiblebut HCl hydrolysis gives cellobiose.

II. FructosansII. Fructosans: :

• They are formed of fructose as a They are formed of fructose as a building unit such as Inulin.building unit such as Inulin.

Inulin:Inulin:• It is formed of fructose only and It is formed of fructose only and

present in onions.present in onions.

• It is not metabolizible in human body, It is not metabolizible in human body, therefore, it is used in evaluation of therefore, it is used in evaluation of kidney function as a part of inulin kidney function as a part of inulin clearance test.clearance test.

III. GalactosansIII. Galactosans::

- They are formed of galactose as the - They are formed of galactose as the building units such as building units such as agar-agaragar-agar..

- - Biochemical importanceBiochemical importance:: 1.1. It is used for growth of bacteria and It is used for growth of bacteria and

mammalian cells in culture.mammalian cells in culture.2.2. It imbibes water and increases It imbibes water and increases

intestinal contents to prevent and intestinal contents to prevent and treat constipation.treat constipation.

3.3. Some electrophoresis gels is formed Some electrophoresis gels is formed of it.of it.

IV. N-acetyl-glucosanIV. N-acetyl-glucosan::

• It is a homopolysaccharide formed of It is a homopolysaccharide formed of --N-acetyl-glucosamine units such as N-acetyl-glucosamine units such as chitin of insects.chitin of insects.

• ChitinChitin: :

• It is a homopolysaccharide formed of It is a homopolysaccharide formed of --N-acetyl-glucosamine units linked by N-acetyl-glucosamine units linked by --1,4-glucosidic linkage present in the 1,4-glucosidic linkage present in the exoskeleton of insects.exoskeleton of insects.

OH

HH

NH-CO-CH 3H

OH

CH 2OH

HO

H

HH

NH-CO-CH 3H

OH

CH 2OH

HO OO

Chitin

-N-acetyl-glucosamine -N-acetyl-glucosamine

n

1 4 14

B-HeteropolysaccharidesB-Heteropolysaccharides• They are polysaccharides that on They are polysaccharides that on

hydrolysis produce several types of hydrolysis produce several types of sugars. There are two types:sugars. There are two types:

1.1. Non-nitrogenous Non-nitrogenous heteropolysaccharidesheteropolysaccharides

2.2. nitrogenous nitrogenous heteropolysaccharides.heteropolysaccharides.

A-Non-nitrogenous heteropolysaccharides:

They do not contain sugar amines such as pectin and plant gums.

1-Plant gums :

• They are exudates of plants that do not contain amino sugars.

• They contain pentoses, hexoses and uronic acids, e.g., Arabic gum which is rich in arabinose.

• They are emulsifying agents.

2. Pectin2. Pectin::• They are present in fruits and are They are present in fruits and are

responsible for settling of jams.responsible for settling of jams.• They are formed of pentoses, They are formed of pentoses,

hexoses, uronic acids mainly hexoses, uronic acids mainly galacturonic acid.galacturonic acid.

• They are water soluble formed from a They are water soluble formed from a water insoluble compound called water insoluble compound called pectosepectose present in raw fruits which present in raw fruits which is transformed into is transformed into pectinpectin by the by the action of sunlight, heat and action of sunlight, heat and pectase pectase enzyme when fruits are ripened.enzyme when fruits are ripened.

• Biochemical importance of pectinBiochemical importance of pectin::

1.1. Emulsifying reagents. Emulsifying reagents.

2.2. Demulcents.Demulcents.

3.3. Responsible for settling of jams.Responsible for settling of jams.

4.4. They increase in size when they They increase in size when they absorb water forming a jell and so absorb water forming a jell and so they are used in the they are used in the treatment of treatment of infantile diarrheainfantile diarrhea..

B-Nitrogenous B-Nitrogenous heteropolysaccharidesheteropolysaccharides::

They contain sugar amines and are of They contain sugar amines and are of two types: two types:

1.1. Neutral nitrogenous Neutral nitrogenous heteropolysaccharidesheteropolysaccharides

2.2. Acidic Acidic nitrogenous nitrogenous heteropolysaccharidesheteropolysaccharides

1-Neutral nitrogenous heteropolysaccharides1-Neutral nitrogenous heteropolysaccharides Glycoproteins or mucoproteinsGlycoproteins or mucoproteins:• They do not contain uronic acids or sulfate They do not contain uronic acids or sulfate

groups (groups (which give acidic characteristicswhich give acidic characteristics).).• They are formed of a large protein core to They are formed of a large protein core to

which are attached smaller branched or which are attached smaller branched or unbranched chains of carbohydrate. unbranched chains of carbohydrate.

• The carbohydrate present include:The carbohydrate present include:HexosesHexoses: mannose, galactose and glucose : mannose, galactose and glucose PentosesPentoses: xylose and arabinose.: xylose and arabinose.Amino sugarsAmino sugars: glucosamine and : glucosamine and

galactosamine.galactosamine.DeoxysugarsDeoxysugars: L-fucose, L-rhamnose and sialic : L-fucose, L-rhamnose and sialic

acid.acid.

Distribution: Glycoproteins are widely distributed in Distribution: Glycoproteins are widely distributed in mammalian tissues. They includemammalian tissues. They include: :

1.1. Mucins of epithelium lining of gastrointestinal, Mucins of epithelium lining of gastrointestinal, urogenital and respiratory tracts are lubricant and urogenital and respiratory tracts are lubricant and protective. protective.

2.2. Cell membranes where they play an important part in Cell membranes where they play an important part in cell-cell attachmentcell-cell attachment..

3.3. Blood group substances A and B antigens.Blood group substances A and B antigens.4.4. Mineral and vitamin transporting protein, e.g., Mineral and vitamin transporting protein, e.g.,

trasferrin.trasferrin.5.5. Immunoglobulins (antibodies), IgG, IgM, IgA….Immunoglobulins (antibodies), IgG, IgM, IgA….6.6. Some hormones, e.g., anterior pituitary hormones: LH Some hormones, e.g., anterior pituitary hormones: LH

and FSH.and FSH.7.7. Some enzymes such as peptidases and alkaline Some enzymes such as peptidases and alkaline

phosphatase.phosphatase.8.8. Intrinsic factor that is responsible for vitamin B12 Intrinsic factor that is responsible for vitamin B12

absorption.absorption.9.9. Structural function as a part of collagen of connective Structural function as a part of collagen of connective

tissue.tissue.

2. Acidic nitrogenous heteropolysaccharidesAcidic nitrogenous heteropolysaccharides

A-Sulfur-free mucopolysaccharidesA-Sulfur-free mucopolysaccharides::

• Their sugar units are not sulfates, Their sugar units are not sulfates, e.g., hyaluronic acid.e.g., hyaluronic acid.

B- Sulfur-containing B- Sulfur-containing mucopolysaccharides:mucopolysaccharides:

• Their sugar units are Their sugar units are sulfated ,e.g.,chondroiten sulfate , sulfated ,e.g.,chondroiten sulfate , HeparinHeparin

Hyaluronic acid: - • It is formed of It is formed of -D-N-acetyl glucosamine linked to -D-N-acetyl glucosamine linked to --

D-glucuronic acid by alternating D-glucuronic acid by alternating -1,3- and -1,3- and -1,4--1,4-glycosidic linkages.glycosidic linkages.

OH

HH

OHH

OH

COOH OH

OH HH

NH-CO-CH 3H

CH2OH

O

O 1 31

4O

H

H

n

-Glucuronic acid -N-acetyl-Glucosamine

Hyaluronic acid

Biochemical importance:

1.1. The molecule is coiled and entwined making a The molecule is coiled and entwined making a very firm gel which prevents bacterial invasion of very firm gel which prevents bacterial invasion of the skin.the skin.

2.2. It is present in connective tissue matrix, vitreous It is present in connective tissue matrix, vitreous humor of the eye, in the skin, synovial fluid, humor of the eye, in the skin, synovial fluid, around the ovum, and in the umbilical cord to around the ovum, and in the umbilical cord to preserve the full-form of these structures.preserve the full-form of these structures.

3.3. Hyaluronic acid imbibes water and forms a Hyaluronic acid imbibes water and forms a incompressible substance due to the presence of incompressible substance due to the presence of several OH groups which creates negative several OH groups which creates negative charges causing repulsion between carbohydrate charges causing repulsion between carbohydrate units enabling the molecule to perform its units enabling the molecule to perform its function as function as lubrication in joint synovial fluids anlubrication in joint synovial fluids an..

• Hyaluronidase Enzyme or Spreading Hyaluronidase Enzyme or Spreading factorfactor: It is the enzyme that hydrolyzes : It is the enzyme that hydrolyzes hyaluronic acid.hyaluronic acid.

• It is present in sperms to help It is present in sperms to help penetration of the ovum and penetration of the ovum and fertilization. fertilization.

• It is present in some virulent strains of It is present in some virulent strains of bacteria that are able spread through bacteria that are able spread through infected wounds.infected wounds.

• It is used in medicine to treat fibrosis It is used in medicine to treat fibrosis and to dissolve mucus.and to dissolve mucus.

• B. Sulfur-containing mucopolysaccharidesB. Sulfur-containing mucopolysaccharides

1-1-Chondroitin sulfateChondroitin sulfate: : it is of three types as followsit is of three types as follows::• Chondroitin sulfate AChondroitin sulfate A::• It is formed of It is formed of -N-acetyl-galactosamine-4-sulfate and -N-acetyl-galactosamine-4-sulfate and -glucuronic -glucuronic

acid linked by alternating acid linked by alternating -1,3- and -1,3- and -1,4-glycosidic linkages.-1,4-glycosidic linkages.

OH

HH

OHH

OH

COOH OHO 3SO

H HH

NH-CO-CH 3H

CH 2OH

O

O 1 31

4O

H

H

n

-Glucuronic acid -N-acetyl-Galactosamine, 4-sulfate

Chondroitin Sulfate A

• Chondroitin sulfate BChondroitin sulfate B::• It is formed of It is formed of -N-acetyl galactosamine-4-sulfate and -N-acetyl galactosamine-4-sulfate and -L--L-

iduronic acid linked by alternating iduronic acid linked by alternating -1,3- and -1,3- and -1,4--1,4-glycosidic linkages.glycosidic linkages.

• L-iduronic acid is the C5 epimer of D-glucuronic acid, i.e., L-iduronic acid is the C5 epimer of D-glucuronic acid, i.e., COOH group at C5 is inside the ring,COOH group at C5 is inside the ring,

OH

HH

OHH

OH

H OHO 3SO

H HH

NH-CO-CH 3H

CH 2OH

O

O 1 31

4O

H

COOH

n

-L-Iduronic acid -N-acetyl-Galactosamine, 4-sulfate

Chondroitin Sulfate B

• Chondroitin sulfate CChondroitin sulfate C: :

• It is formed of It is formed of -N-acetyl galactosamine-6-sulfate -N-acetyl galactosamine-6-sulfate and and -glucuronic acid linked by alternating -glucuronic acid linked by alternating -1,3- -1,3- and and -1,4-glycosidic linkages.-1,4-glycosidic linkages.

• Present in cornea of the eye, tendons, ligaments, Present in cornea of the eye, tendons, ligaments, bones, cartilage and connective tissue matrix.bones, cartilage and connective tissue matrix.

• They absorb water, form incompressible They absorb water, form incompressible substances by means of their ionizable OH and substances by means of their ionizable OH and sulfate groups, creating negative charges leading sulfate groups, creating negative charges leading

to repulsion between the moleculesto repulsion between the molecules..

OH

HH

OHH

OH

COOH OOH

H HH

NH-CO-CH 3H

CH 2OSO 3H

O

O 1 31

4O

Chondroitin Sulfate C

H

H

n

-Glucuronic acid -N-acetyl-Galactosamine, 6-sulfate

2. Heparin:Heparin:Structure:Structure: It is formed of a long repeat of sulfated It is formed of a long repeat of sulfated --

glucosamine and sulfated glucosamine and sulfated -L-iduronic acid linked by -L-iduronic acid linked by alternating alternating - and - and -1,4-glycosidic linkages, synthesized on -1,4-glycosidic linkages, synthesized on a core protein. a core protein.

SourceSource: It is produced by mast cells (kidney, lung, liver skin).: It is produced by mast cells (kidney, lung, liver skin).

OH H

H

NH-SO 3HH

OH

CH 2OSO 3H

HO

H

HH

OSO 3HH

OH

H

COOHOO

O

n

Heparin

1 4 14

-Glucosamine, N- and 6-sulfated -L-Iduronic acid, 2-sulfate

• FunctionFunction: : 1.1. It is an anticoagulant and prevents intravascular It is an anticoagulant and prevents intravascular

clotting. It interferes with the activated clotting clotting. It interferes with the activated clotting factors (thrombin, IX, X, XI and XII) in coagulation, factors (thrombin, IX, X, XI and XII) in coagulation, through activation of antithrombin III that inhibits through activation of antithrombin III that inhibits the intrinsic pathway of blood clotting. Therefore, it the intrinsic pathway of blood clotting. Therefore, it is used in cases of increased coagulability, e.g., is used in cases of increased coagulability, e.g., cardiac ischemia or deep venous thrombosis.cardiac ischemia or deep venous thrombosis.

2.2. It binds activates lipoprotein lipase enzyme (the It binds activates lipoprotein lipase enzyme (the plasma clearing factor) to clear the turbid plasma plasma clearing factor) to clear the turbid plasma from the absorbed lipids after meals. from the absorbed lipids after meals.

3.3. It regulates the action of the heparin-binding growth It regulates the action of the heparin-binding growth factors.factors.

4.4. It has a structural role in extracellular matrix. It It has a structural role in extracellular matrix. It affects cell-cell and cell-matrix interaction to affects cell-cell and cell-matrix interaction to modulate development, cell proliferation, apoptosis modulate development, cell proliferation, apoptosis and differentiation.and differentiation.

Chemistry of carbohydrates