Serkan SAYINER, DVM PhD. Assist. Prof.Near East University, Faculty of Veterinary Medicine, Department of Biochemistry

serkan.sayiner@neu.edu.tr

CARBOHYDRATES

Carbohydrates (KH) are most commonly found in nature,

with three major groups of organic substances together

with proteins and lipids found in living materials.

The CHs, which are generally called as sugars, are not

sweet when they are as large molecules.• For example, starch, a polysaccharide, is not sweet, while

glucose, a monosaccharide, is sweet.

Overview

It is found entirely in plants and animals.• The most common carbohydrates found in the plants are firstly

cellulose and secondly starch. While cellulose has function assupportive and preservative, the starch has the foodstuff. The same task is undertaken in humans and animals by glycogen.

The sugars are broken to their simplest units that build upthemselves in the digestive system. After that, they are absorbed.

The energy required for metabolism is mainly derived from Glucose breakdown.

Overview

Carbohydrates are generally composed of C, H and O

elements.

H and O atoms are generally found like in water. That's

why it means carbonated water.• Over time, however, studies have shown that not all

carbohydrates comply with this formula, or the presence of non-

carbohydrate substances has been found to fit the formula.

Definition of Carbohydrates

CnH2nOn Cn(H2O)n C2H4O2 C6H15O5Acetic acid Rhamnose

The C, H and O atoms are actually in the structure of

some functional groups. These are aldehyde, ketone,

primary alcohol and secondary alcohol groups.

Only one of the aldehyde and ketone groups is

present in the building. Neither can exist.

Primary and secondary alcohol groups are

complementary to other carbons of CHs. They are many

alcoholic aldehydes or very alcoholic ketones.

Definition of Carbohydrates

H C O

Aldehyde group

C O

Ketone group

H C OH

Secondaryalcohol group

H C OH

HPrimary alcohol

group

CHs is defined as;• Aldehyde or ketone derivatives of polyhydroxylic

alcohols (Monosaccharides),

• Their polymers (Di, oligos and polysaccharides),

• Oxidation products (Sugar acids),

• Reduction products (Sugar alcohols),

• Substitution products (Amino sugars) and the sulfate

and phosphate esters.

Definition of Carbohydrates

Monosaccharides or simple sugars

Di-oligosaccharides• Consist of 2-10 monosaccharide unit. If 2, it is called Di. If 3-10, it is

called oligosaccharides.

Polysaccharides• They are formed by the polymerization of a large number of

monosaccharides. It can be a simple chain, but also shows

branched complex structures and different structures.◦ Homopolysaccharides

◦ Heteropolysaccharides

Classification of Carbohydrates

They are aldehyde or ketone derivatives of polyhydroxy alcohols and it is not possible to separate them into simpler molecules when they are hydrolyzed.

• There are one aldehyde or ketone group per molecule in the structure. These groups are also belonged to carbonyl group.

• Aldose and Ketose?◦ Monosaccharides which are containing aldehyde group are called Aldose.

◦ Monosaccharides which are containing ketone group are called Ketose.

Monosaccharides

-ose ? • When the monosaccharides are named in Latin, they are

brought to the end of the name «-ose» suffix.

Monosaccharides are also named according to the

number of carbon atoms they contain. For example, if

it contains 3 C atoms, it takes the name trio.

A monosaccharide containing a 3-carbon and an

aldehyde group is called Aldotriose.

Monosaccharides

The most common

monosaccharides in

nature and organisms

are 3, 5 and 6 carbons.

Those with 4 and 7

carbons are synthesized

in the intermediate

metabolism, which are

rare.

Monosaccharides

C number Aldose Ketose

C3 Triose Glyceraldehyde Dihydroxyacetone

C4 Tetrose Erythrose Erythrulose

C5 Pentose Ribose Ribulose

Xylose Xylulose

C6 Hexose Glucose Fructose

Mannose

Galactose

C7 Heptose Sedoheptulose

Closed Formulas:

Formation of Monosaccharides

C6H12O6 CH2OH-(CHOH)4-CHO

According to this formula, we can

see that 4 of the 6 carbons are

the secondary alcohol group, 1 is

the primary alcohol group, 1 is

the aldehyde group (-CHO). So it's

an Aldohexose.

According to this formula

we can say that the

carbohydrate is only a

Hexose because it has 6

carbons.

Structure formula:• It is a form that shows the space alignment of

the groups.

• The C atom containing the aldehyde group is

defined as the 1st C atom, the C atom carrying

the primary alcohol group is defined as the 6th

C atom.

• It is not clear which KH is defined in this formula.

We can only say that it is an Aldohexose.

Formation of Monosaccharides

C

C

C

C

C

C

OHH

OHH

OHH

OHH

OH

H2OH

1

6

2

3

4

5

Configuration Formulas:• It is the shape which shows the

positions of the H and OH groups in the space. Depending on the lengthwise arrangement of the H and OH groups, several CHs may formsuch as Glucose, mannose, galactose.

• Stereoisomers which are differing in its configuration at only one chiral carbon atom are called as Epimers. ◦ For example, glucose and galactose are

Epimers of each other, as they differ in only in the position of hydroxyl group at C4.

Formation of Monosaccharides

Glucose

C

C

C

C

C

C

OHH

HHO

OHH

OHH

OH

H2OH

1

6

2

3

4

5

Fructose

CH2OH

C

C

C

C

C

O

HHO

OHH

OHH

H2OH

1

6

2

3

4

5

Herman Emil Louis Fischer• 1902 Nobel Prize in Chemistry

According to this projection;• In the vertical plane, C1 is drawn at the top of C

chain and C6 at the bottom (If it is hexose).

Fischer Projection

9 Oct. 1852 - 15 July 1919

• In an aldose, the carbon of the aldehyde group is C1; in a ketose the carbon of the ketone group has the lowest possible number (usually C2).

• In this project, the L- and D- structures are also distinguished.

• Mainly monosaccharides and also amino acids and other organic compounds, used showed by using this project.◦ Especially in stereochemistry, the enantiomers of chiral molecules are

shown.

C

C

C

C

C

CH2OH

O

H

OH

H

OH

H

H

HO

HO

H

Formation of Monosaccharides

Mannose GalactoseGlucose

Fis

cher

Pro

jecti

on

C

C

C

C

C

CH2OH

O

H

H

OH

OH

H

HO

HO

H

H

C

C

C

C

C

CH2OH

O

H

OH

OH

OH

H

H

HO

H

H

1

6

2

3

4

5

1

6

2

3

4

5

1

6

2

3

4

5

Ring Formulas (Howarth Projection)• This form of formulation is only relevant for pentoses and

hexoses.

• Asymmetric Carbon Atom: When four atoms of the carbon

atom are bonded to four valences, they are called

asymmetric carbon atoms.

• It is seen that the first and sixth C atoms of the

monosaccharides are not asymmetric and the remaining 4 C

atoms of the second group of alcohols are asymmetric. The

substances with asymmetric carbon atoms show

Stereoisomerism.

Formation of Monosaccharides

• 2n= Number of stereoisomers

• Related to stereoisomerism; It is evident that they form

different molecules even though they have the same

structural formula.

◦ There is a relationship between the asymmetric C atom in

the stereoisomers.

◦ Accordingly, if there are 4 asymmetric carbon atoms, the number

of stereoisomers is 24 = 16.

◦ However, the investigations have shown that hexoses are not 16

but 32 isomers.

◦ That is, 25 = 32. In this case, it is supposed to be the fifth

asymmetric carbon atom. Where is it?

Formation of Monosaccharides

• The substances with asymmetric carbon atoms are polarized to

the right, to the left. This is called specific rotation.

• What is a Mutorotation? ◦ The specific rotation of the polarimeter is + 112° after dissolving the

glucose in the room temperature. If the same glucose is dissolved at

90ºC, it is determined that the specific rotation is + 19º. Both

solutions find a balance at + 52.5º after some time. This is called

mutarotation.

• If glucose gives two different rotations it has two different forms. This

happens because of a fifth asymmetric C atom. This is possible with

the formation of hemiacetals of aldehydes.

Formation of Monosaccharides

Sir. Walter Norman Haworth• 1937 Nobel Prize in Chemistry

According to this projection;• The cyclic structure of monosaccharides are presented (5

and 6 C numbered ones).

• Carbon is the implicit type of atom. Carbon 1 is known as the anomeric carbon.

• Hydrogen atoms on carbon are implicit.

• A thicker line indicates atoms that are closer to the observer.

• The groups below the plane of the ring in Haworth projections correspond to those on the right-hand side of a Fischer projection.

Howarth Projection

19 March 1883 -19 March 1950

When the ring forms, the fifth asymmetric carbon atom

is formed.

This is possible when the aldehyde group is converted

into a semi-acetal (hemiacetal) structure.

The asymmetric C atom is the 1st C atom.• At the 4-valence of the 1st C atom, 4 different groups are

connected, one of them is the OH group.

Formation of Monosaccharides

α-Glucose+ 112 º

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

β-Glucose+ 19 º

C

C

C

C

C

C

OHH

HHO

OHH

O

H

H

H2OH

1

6

2

3

4

5

HO

Glucose+ 52,5 º

C

C

C

C

C

C

OHH

HHO

OHH

OHH

OH

H2OH

1

6

2

3

4

5

The space position of OH group bound to the first C atomdetermines the whether an hexose or pentose is alpha or beta.• One the right, it is called ALFA hexose or pentose,• On the left, it is called BETA hexose or pentose.

Carbohydrates; • ALFA and BETA forms are defines as anomer, • The C atom that makes up these forms is called the anomeric C

atom.• The OH group linked to the first C atom is called the free

hydroxyl group. This group is also the group that has the ability to reduce in carbohydrates.

• Carbohydrates with a free OH group have reducing properties.

Formation of Monosaccharides

β-Glucose α- Glucose

1

23

4

5

6

1

23

4

5

6

Howarth Projection

Substances having asymmetric carbon atom or atoms

have often their mirror images due to the different

sequences of the groups they carry.

These type of compound called geometric isomers or

more common stereoisomers. The association of such

compounds is also referred to as stereoisomerism.

Optical Isomerism

Stereoisomeric materials are also optically active substances. Optically active substances are substances that can turn the polarized light to the right or left.

Two stereoisomeric optics-enantiomers- rotate the polarized light at the same level, but in opposite directions (right and left)• Ordinary light consists of electromagnetic waves that oscillate in all planes

perpendicular to the direction in which the light travels. Passing light through a polarizer allows light in only one plane to come through. This is plane-polarized light (or simply polarized light), and it has an electric vector that oscillates in a single plane. A polarimeter is an instrument that allows plane-polarized light to travel through a sample tube containing an organic compound. After the light exits the sample tube, an analyzer slit is rotated to determine the direction of the plane of the polarized light exiting the sample tube.

Optical Isomerism

D-glyceraldehyde turns the

light to the right; L-

glyceraldehyde turns the

light to the left. So these are

dextrorotatory and

levorotatory because of

these features.

Optical Isomerism

The (+) and (-) signs after the letters D and L indicate

the ability to turn the light right and left.

D (+) Glyceraldehyde

C OH

C

CH2OH

OHH

C OH

C

CH2OH

HHO

L (-) Glyceraldehyde

Since glyceraldehyde contains one asymmetric C atom, the right-to-left translational property of the light is easily determined.

However, when carrying more than one asymmetric carbon atom, the D - L shapes are not related to turning to the right and to the left.

In sugars containing more than 3 C atoms, the D and L forms are named according to the glyceraldehyde resemblance, followed by the (+) and (-) positions by determining the direction of breaking the light.• For example, D (+) glucose means that groups linked to the 5th C

atom, which is the closest asymmetric carbon atom to the primary alcohol group of glucose, resemble D-glyceraldehyde, and the light breaks to the left.

Optical Isomerism

D (+)L (-)

They are easily soluble in water and aqueous media. The

aqueous media they dissolve exhibit different properties

according to their neutrality, alkalinity and acidity and

give different reactions.

They show a slow mutorotation in water and neutral

aqueous media.

In very mildly alkaline environment, mutarotation is

accelerated.

Certain monosaccharides in a slightly alkaline environment

(at 0.05 N) are converted to other monosaccharides via enol

forms. This is called enolization.

Solubilities of Monosaccharides

Enolization is a general phenomenon of aldehydes and ketones.

The migration of a proton from a C atom to the oxygen of a neighboring carbonyl group (aldehyde or ketone group) is called enolization to form unsaturated alcohol, an enol.

The products that come after this event are called enediol.

Solubilities of Monosaccharides

In strongly alkaline environments, the reaction

capabilities of enodiol forms are very high.

In highly alkaline environments, if the monosaccharide

solutions are boiled after being thoroughly mixed, color

changes in the form of red brown.

At the end of the color change, some resin-like

substances are formed. At this time, caramel is smelled.

Solubilities of Monosaccharides

Ası T. Tablolarla Biyokimya Cilt I

MOORE Experiment

In acidic environments, the first reaction is the acceleration of mutorotation. Monosaccharides become carbonized if the temperature is raised to boiling temperature in severe acid environments.

Some of the aromatic compounds are characterized by color reactions with monosaccharides and are thus used to recognize those monosaccharides.

In a concentrated acid medium, the monosaccharide molecule boils to dehydrate by losing 3 M of water. As a result, furfural from pentoses, 5-hydroxy-methyl furfural from hexoses.

Solubilities of Monosaccharides

The most important feature is that they give color

reactions to condense with some aromatic compounds

such as orcin, fluoroglucin, resorcin, alpha-naphthol.

The pentoses turn to green with orcin, to red with

floroglucine, and they help to recognize the pentoses.

Seliwanoff (resorcin, pink, ketohexose), Molisch assay

(alpha-naphthol, violet, general carbohydrate

recognition experiment).

Solubilities of Monosaccharides

Sweetness of

Monosaccharides

Fructose 173,3

Sucrose 100,0

Glucose 74,3

Xylose 40,0

Maltose 32,5

Galactose 31,1

Lactose 16,0

Sweetness of Monosaccharides

Monosaccharides are sweet substances.They take the tastes from alcohol groups they carry.

The sucrose taste is regarded as 100 and the flavors of other sugars are graded.• Sugar comes in taste in the term.

Actually, sugar is the saccharide we call it. Tea or tableware. It is a disaccharide.

Monosaccharides and certain disaccharides are strongly reducing agents, especially at high pH, i.e. in alkaline environments.

These properties come from the free aldehyde and ketone groups they carry.

Reduction Properties of Monosaccharides

Glucose

C

C

C

C

C

C

OHH

HHO

OHH

OHH

OH

H2OH

1

6

2

3

4

5

Fructose

CH2OH

C

C

C

C

C

O

HHO

OHH

OHH

H2OH

1

6

2

3

4

5

They reduce Ag+, Hg+++, Bi+++ and Cu++ ions easily.

In the meantime they are oxidized and bring acid

mixtures to the field.

If these reactions are carried out with the addition of

the color-oxidizing agent, it will become reddened as

color change will occur when reduced by the

monosaccharides

Reduction Properties of Monosaccharides

Glycoside formation• When the ring structures of the monosaccharides are combined

with the phenol groups or the alcohol by using HCl as the

catalyst, the glycosides are formed.

• A bond formed between a monosaccharide aldehyde group

and another monosaccharide alcohol group that will result

in the formation of a glycoside is called a glycoside bond.◦ Most natural glycosides are found in plants.

Properties of Monosaccharides on -OH Groups

Ether Formation• H, found in -OH group, substitute with alkyl group.

Ester Formation• The esterification of the OH groups with acids forms the sugar

esters.

• The phosphate esters they form with phosphoric acid are of

biological importance. They are involved in the Metabolism of

carbohydrate and the nucleic acid composition.

Properties of Monosaccharides on -OH Groups

Ester Formation

Properties of Monosaccharides on -OH Groups

Monosaccharide Ester Reaction Phosphate Ester Derivatives

Glucose Esterification of -OH group in the 1st C with

H3PO4

Glucose-1-Phosphate (G-1-P)

(Cori ester)

Glucose Esterification of -OH group in the 6th C with

H3PO4

Glucose-6-Phosphate (G-6-P)

(Robinson ester)

fructose Esterification of -OH group in the 6th C with

H3PO4

Fructose-6-Phosphate (F-6-P)

(Neuberg esteri)

fructose Esterification of -OH group in the 6th and 1st C

with H3PO4

Fructose-1,6-diphosphate (F-1,6-P)(Harden-Young ester)

Amino Sugars• An amino sugar (or a 2-amino-2-deoxysugar) is a sugar

molecule in which a hydroxyl group (mostly in 2nd C) has

been replaced with an amine group (NH2).

• It is named according to which monosaccharide is bound to the

amine group. Example. Glucose glucosamine and galactose

galactosamine..

Important Sugar Derivatives

Amino sugars Places of involvement Tissues

GlucosamineHyaluronic Acid, Heparin, Mucoproteins,

blood group substancesKitin, cell wall in fungi

Galactosamine Chondroitin sulphatesCartilage, bone, tendon,

cornea

Amino Sugar Acids• Most of the amino acids present in the nature are acetylated.

In other words, it is the N-acetyl derivatives of amino

sugars. That is, they are bonded with acetic acid through the

amine group. Example: N-acetyl-glucosamine.

• Amino sugars and amino sugar acids are generally involved in

the incorporation of carbohydrate polymers.

Important Sugar Derivatives

• Amino sugar acids which are physiologically important are

neuraminic acids, sialic acid and mumaric acid.◦ Neuraminic acid is a 9 C sugar acid formed by the condensation of 3 C

pyruvic acid with 6 C mannosamine.

Important Sugar Derivatives

Amino sugar acids Places of involvement Tissue

Neuraminic acidPyruvic acid + Mannosamine,

Mucopolysaccharides, glycoproteinsHuman milk

N-acetyl-Neuraminic acidPyruvic acid + N-acetyl Mannosamine,

Bacterial enzymes

Bacteria, blood

group, serous

secretions

Sialic acidN-and O-acyl derivatives of neuraminic acid.

Some lipids, polysaccharides and mucoproteinsin textures

Mumaric acidLactic acid + N-acetyl Glucosamine,

Heteropolysaccharides

Bacterial

membranes

Neurominic Acid N-acetyl-Neurominic Acid

Sialic Acid

Deoxy Sugars• Deoxy sugars are sugars that have had a hydroxyl group

replaced with a hydrogen atom

Important Sugar Derivatives

Deoxy sugars Places of involvement Tissues

Deoxyribose Nucleic acids In cells

RhamnoseSome oligosaccharides, blood group substances,

mucopolysaccharidesMilk, bacteria

stiffness

Fucose In various compounds Plants

Ribonucleotide reductase

Sugar Alcohols• It occurs when monosaccharides are reduced to alcohol groups

in aldehyde or ketone groups. Glucose sorbitol, mannose

mannitol, glyceraldehyde glycerol .

◦ The aldehyde groups forming the 1st carbon of aldoses change to

the primary alcohol group.

◦ The ketone groups forming the 2nd carbon of ketoses change to the

secondary alcohol group.

Important Sugar Derivatives

Important Sugar DerivativesSugar alcohols Monosaccharide Attended / used places

Sorbitol Glucose, FructosePolyol Pass, Food additives,

laxatives, cosmetics

Glycerol Glyceraldehyde, Dihydroxyacetone Lipids (Triglycerides)

Mannitol Mannose Therapeutic?

Dulsitol (Galaktitol) Galactose Cataract cause?

Ribitol Ribose Riboflavin(B2)

Eritrol Erythrose Food additive

Sugar Acids• Oxidation products of monosaccharides. There are very

important members in the biological direction. They are monosaccharides with a carboxyl group.◦ Aldonic, Saccharic and Uronic Acids.

• Aldonic Acids◦ The aldehyde group on the 1st carbon atom of the aldoses is

oxidized and changes to the COOH group.

◦ The hexoses are Hexonic Acids. Glucose gluconic acid, galactose galactonic acid.

◦ *Gluconic acid is an important intermediate metabolite in the synthesis of pentoses.

Important Sugar Derivatives

• Saccharic Acids (Aldaric Acids)◦ Aldehydes are oxidized to the COOH group by oxidizing the primary

alcohol groups in the 6th carbon with the aldehyde groups in the 1st

carbon.

◦ Glucaric acid is formed by this oxidation of glucose.

◦ Mannose Mannaric acid.

◦ Galactose Galactic (Musik) acid.

◦ Ribose Ribosaccharic Acid

◦ They have no biological significance.

Important Sugar Derivatives

• Uronic Acids◦ They are sugars in which the terminal carbon's hydroxyl group

(primary alcohol group) has been oxidized to a carboxylic acid.

◦ The product of glucose is glucuronic acid.– Hexoses are hexuronic acid and are the most common glucuronic acid.

– It is found in the structure of glycoproteins and mucopolysaccharides.

– Takes part in detoxification events. It serves to remove toxic substances.

◦ Mannose → Mannuronic acid.

◦ Galactose → Galacturonic acid

Important Sugar Derivatives

A disaccharide is the sugar formed when two monosaccharides are joined by glycosidic linkage. The joining of two monosaccharides happens by a condensation reaction, which involves the elimination of a water molecule.

Its general formula is Cn(H2O)n-1.

When disaccharide occurs, binding of the monosaccharides occurs with the glycosidic linkage. The oxygen bridge formed by the association of two monosaccharides is called the glycosidic bond.

Disaccharides

The monosaccharide molecule binds to each other in

two forms to form glycosides..• Maltose Type Bonding: It is formed by bonding a carbonyl

group (aldehyde or ketone group) of a monosaccharide with an

alcohol group of an another monosaccharide.◦ For example: Maltose and lactose.

• Trehalose Type Bonding: It is formed by bonding a carbonyl

group (aldehyde or ketone group) of a monosaccharide with a

carbonyl group of an another monosaccharide.◦ For example: Sucrose.

Disaccharides

Maltose type bonding;• When at least one of the monosaccharides is free of an

aldehyde or ketone group, the disaccharides with this type of

linkage have a reducing property.

In disaccharides with trehalose type bonding;• Since both carbonyl groups of monosaccharides are used for

linking, there is no reducing property.

Disaccharides

α-glycoside bond and β-glycoside bond• Alpha and beta monosaccharides are formed according to the

configuration of OH groups.

• If the α-monosaccharide OH group is used in the glycoside

bond, it is named α-glycoside bond.

• If the OH group of β-monosaccharide is used, it is named β-

glycoside bond.

Disaccharides

• When the glycosidic bond is shown, it is also shown which carbon atoms have taken place in the bond.

• If the linkage is between the OH group in the first carbon of the α-monosaccharide and the secondary alcohol in the fourth carbon of the other monosaccharide, then this linkage is α; 14 glycoside.

• The connection is of great importance in the form of α- and β-. Because the same monosaccharides and disaccharides vary depending on whether the link between the same carbon atoms is alpha or beta. Examples include Maltose and Cellobiose.

Disaccharides

Disaccharides Monosaccharides Glycosidic link

α – Maltose α –Glucose+ α – Glucose α ; 1 4

β – Maltose α –Glucose+ β – Glucose α ; 1 4

Cellobiose α –Glucose+ β – Glucose β ; 1 4

α – Lactose α –Glucose+ β – Galactose β ; 1 4

β – Lactose β –Glucose+ β – Galactose β ; 1 4

Sucrose α –Glucose+ β –Fructose α ; 1 2

Disaccharides

It is also called malt sugar.

Two glucose molecules are linked via α; 1 → 4

glycosidic bond. Glucose molecules may be α-glucose in

either case, such as α-glucose or β-glucose. The result is

two forms, α- and β-maltose.• α-Maltose:The two molecules merge into a mixture of α-

glucose.

• β-Maltose: A molecule is formed by the combination of α-

glucose and a molecule β-glucose.

Maltose

In the α-maltose and β-maltose, the glucose bond is

between carbons 1 and 4. Link is α;1→4 glycosidic bond.

One of the aldehyde groups is free, so it has reducing

properties.

Maltose is the disaccharide unit of starch and glycogen.

It is sweet and easy to dissolve in water.

Maltose

α-Maltose

O

α-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

α-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

α; 14 Glycosidicbond

α-Glucose α-Glucose

O

α-Maltose

α; 14 Glycosidic bond

1

23

4

5

6

1

23

4

5

6

β-Maltoseα-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

β-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

H

H2OH

1

6

2

3

4

5

HO

α; 14 Glycosidicbond

α -Glucose β -Glucose

O

β-Maltose

α; 14 Glycosidic link

1

23

4

5

6

1

23

4

5

6

The two glucose molecules are linked via β;1→4 glycosidic bond.• It is composed of an α-Glucose and a β-Glucose.

It is plant origin and does not exist freely in nature.

Cellobiose is the disaccharide unit of the cellulose polysaccharide.

One of the aldehyde groups is free (which is in α-glucose), so it has reducing properties.

Cellobiose

α-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

β-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

H

H2OH

1

6

2

3

4

5

HO

O

Cellobiose

β; 14 glycosidicbond

α-Glucoseβ-Glucose

O

Cellobiose

β; 14 glycosidic bond

1

23

4

5

6

1

23

4

5

6

It is also referred to as the milk sugar because it is only

present in the milk in considerable quantities.

Synthesized by mammary glands. • If too much lactose is produced or the milk is not as fast as its

capacity, it will pass to the blood. The organism can not use

unhydrolyzed disaccharides. Unused lactose is excreted in the

urine. This is called lactosuria.

It is one of the two disaccharides found freely in nature

along with sucrose.

Lactose

Lactose is a disaccharide formed by β;1→4 glycosidic

bonding between Glucose and galactose

monosaccharides.

There are two forms; α-Lactose and β-Lactose.• Galactose is β- in both lactoses.

• Depending on whether the glucose is in the α- or β- position,

α-lactose and β-lactose occurs.

Lactose

One of the aldehyde groups is free (which is in glucose),

so it has reducing properties.

It is found 5% in the milk.

The various microorganisms found in the milk can

convert lactose to lactic acid which causes the souring

of milk.

Lactose

O

α-Lactoseβ-Galactose

C

C

C

C

C

C

OHH

HHO

HHO

O

H

H

H2OH

1

6

2

3

4

5

HO

α-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

β; 14 glycosidicbond

α-Glucoseβ-Galactose

O

α-Lactose

β;14 glycosidic bond

1

23

4

5

6

1

23

4

5

6

O

β-Lactoseβ-Galactose

C

C

C

C

C

C

OHH

HHO

HHO

O

H

H

H2OH

1

6

2

3

4

5

HO

β-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

H

H2OH

1

6

2

3

4

5

HO

β; 14 Glycosidicbond

β-Glucoseβ-Galactose

O

β-Lactose

β; 14 glycosidic bond

1 4

It is also called table sugar. Also known as sugar cane.

It is a disaccharide formed by α;1→2 glycosidic bond between glucose and fructose monosaccharides.

It is plant origin. It is found mostly in sugar beet and sugar cane. It is found in the majority of fruits and sugars. It's pretty sweet.

It does not have a reducing property because it does not have a free aldehyde and ketone group.

Sucrose (Saccharose)

The hydrolysis of sucrose with acids occurs more rapidly

than all other disaccharides. • If lactose hydrolysis with an acid is 100, maltose becomes 127

and sucrose becomes 1240.

• The sucrose normally turns the polarized light to + 66.5º right.

But after being hydrolyzed by a special enzyme called

saccharase, turns the polarized light to -39.5º left. This

phenomenon occurs after the hydrolysis of sucrose, resulting in

glucose and fructose units. Fructose turns to the left - 92.5

degrees. Glucose turns right +52.8º. So fructose turning degree

is higher than glucose.

Sucrose (Saccharose)

If heated to 200° C, water is lost and becomes a brown amorphous mass. It's called caramel.

It can be used by the body when given by mouth.

Saccharose and glucose are the most important sugars in our nutrients. The monosaccharides obtained after hydrolysis ofsucrose, is absorbed easily and used for various purposes.• When disaccharides (including lactose, sucrose) are administered

directly to the blood, the body can not benefit from them and they are excreted in urine like a foreign substance.

Sucrose (Saccharose)

O

α-Glucose

C

C

C

C

C

C

OHH

HHO

OHH

O

H

OH

H2OH

1

6

2

3

4

5

H

Sucrose

α; 12Glycosidic bond

β-Fructose

CH2OH

C

C

C

C

C

OHHO

OHH

HO

H

H2OH

1

6

2

3

4

5

α-Glucose β-Fructose

Sucrose

α; 12 Glycosidic bond

1 2

Two α-D-glucose units are condensed by α;11

glycosidic bond.

It is founf hemolymph of many bugs.

Two anomeric C atoms consist of glycosidic bond, so it is

not reducible.

Trehalose

α-Glucose α-Glucose

Carbohydrates formed by polymerization of several monosaccharides

(more than two, less than 10)

It is a trisaccharide composed of galactose, glucose

and fructose.

It is found in sugar beet, and in highly organized plants.

It is formed by 1 molar galactose binding to saccharose.

It is the most abundant oligosaccharide found in plants

after sucrose.

Raffinose

It is a trisaccharide with no reducing properties and synthesized by many plant extract feeding insects.

It plays a role in reducing stress caused by osmosis in insects.

Melezitose is found in the content of leaf juice (honeydew) secreted by the leaf bit. This sap is pretty sweet and is a source of attraction for ants. It is also a food source for bees.

Melezitose

It is formed by the attachment of 1 molar galactose to the galactose unit of Raffinose with the α;1-6 glycosidicbond.

It is a tetrasaccharide found in plants.

Stachyose occurs naturally in numerous vegetables (e.g. green beans, soybeans and other beans) and other plants. It is less sweet than sucrose. It is mainly used as a bulk sweetener or for its functional oligosaccharide properties.

Stachyose

The carbohydrates that are formed by the addition of at

least ten monosaccharide molecules to one another via

the glycosidic bond are called polysaccharides.

They are not sweets.

Molecular weights are high.

The shapes may be straight-chain, branched, or ring-

shaped.

Polysaccharides

Polysaccharides are also called glycans. They are examined in two groups.• Homopolysaccharides or homoglycans

• Heteropolysaccharides or heteroglycans

Derivative monosaccharides can participate to the structure.• Chitin: A homopolysaccharide composed of glucosamine units, which are

amino sugar.

• Hyaluronic Acid: A heteropolysaccharide composed of glucosamine and glucuronic acid units.

Polysaccharides

Homopolysaccharides Heteropolysaccharides

Glycogen Blood group items

Starch Hyaluronic Acid

Cellulose Chondroitin sulfate

Inulin Heparin, Heparan sulphate

Kitin Arab glue

Dextrans Pectin

Dextrins Murein

Agar-agar

Polysaccharides

Homopolysaccharides are polysaccharides (polymers)

composed of a single type of monosaccharide or

monosaccharide derivative.

The suffix '-an' is used instead of '-ose'.• When all units are glucose, homopolysaccharide is called

glycan.

• If all units are xylose and homopolysaccharide is called xylan.

• If all units are mannose, homopolysaccharide is called mannan.

• If all units are galactose homopolysaccharide is called galactan.

Homopolysaccharides

If it includes pentose units, it is called pentosan; hexose

units hexosan.

Some important homopolysaccharides from the

biological front have special names. Starch, Glycogen,

Cellulose.• They consist of glucose units.

• So they are glycan and hexosan.

• They are always known by their private names.

Homopolysaccharides

It is the carbohydrate stored in plants. There are plenty of

sources like wheat, potatoes, rice, corn, pods, nuts,

peanuts, fruits and vegetables.

Humans and animals take plenty of starch.

When hydrolyzed, it gives glucose monosaccharide units.

The molecular structure is made up of two parts which

differ in some aspects. Amylose and Amylopectin.

Starch

Amylose• It's a straight chain.

• It forms about 28-30% of the molecule. It contains 250-300

glucose units.

• Glucose units are linked up with α;1→4 glycosidic bonds.

• They are long chains that are prone to spiral formation.

Starch

Amylopectin• The second shape of the molecule shows a branched structure.

• It forms 70% of starch.

• There are at least 1800 glucose units in the structure.

• Glucose units are linked up with α; 1 → 4 and α; 1 → 6

glycosidic linkages.

Homopolysaccharides; STARCH

1 4

1

6

• Glucose units are linked in a linear way with α;1→4

glycosidic bonds. Branching takes place with α;1→6

glycosidic bonds occurring every 24 to 30 glucose units,

resulting in a soluble molecule that can be quickly degraded

as it has many end points onto which enzymes can attach.

• Its counterpart in animals is glycogen, which has the same

composition and structure, but with more extensive branching

that occurs every eight to 12 glucose units.

Homopolysaccharides; STARCH

Amylose

Amylopectin

Kaynak: Eberly College of Science

Enzymes that hydrolyze starch are called amylases.

There are two types of amylases, α-amylase and β-

amylase.

α-amylase is found in pancreatic secretion and saliva.• Except for the maltose glycoside linkage, α; 14 glycosidic

bonds are randomly broken.

• Mixture of glucose and maltose in the medium is formed.

Starch

Β-amylase is found in plants and catalyses the following

chemical reaction.• Hydrolysis of α;14 glycosidic linkages in polysaccharides so

as to remove successive maltose units from the non-reducing

ends of the chains. This enzyme is also called maltose-

hydrolase.

These two enzymes affect the amylopectin, but the

straight chains dissolve to branching points and they do

not broke α;16 glycosidic bond.

Starch

When the amylose is under the influence of α-amylase,

the amylose-chain comes broken down. The final

product remains a mixture of glucose and maltose.

When the amylose is under the action of β-amylases,

the final product is almost exclusively maltose. It

shows its effect to start from the non-reducing end.

Starch

When amylopectin is under the action of β-amylases, it

is broken down into maltose molecules, starting from

the non-reducing ends of the molecule. The

fragmentation stops when it reaches the branching

point. Because do not act on the α;16 glycosidic bond.

Since the β-amylase can not exert its effect, the

remaining portion of the starch after enzyme

hydrolysis is called Dextrin.

Starch

Ası T. Tablolarla Biyokimya Cilt I

These branching points can only be broken by a special enzyme. The name of this enzyme is α;1,6-glucosidase or debranching enzyme.

It is also called limit dextrin. They carry about 700 glucose units. Starch is soluble in water.

Limit dextrin solutions are used as mucilage. It is used for the feeding of children because it is easily digested and the stomach prevents milk clotting.

Starch

When the amylopectin is hydrolyzed by the action of α-amylase, the chain is randomly cleaved.

As a final product, a mixture of branched and unbranched small molecules is formed.

In this mixture, a large amount of oligosaccharides are found which contain α;16 glycosidic linkages. Besides these, maltose is present in the mixture in the molecules.

Starch

Both starch and its degradation products give

characteristic colors with iodine solution.• Amylose gives blue-black,

• Amylopectin gives purple-red,

• Dextrins gives red,

• Smaller molecular dextrins give colorless solutions.

These colors disappear when heated and re-emerge

when cooled.

Starch

It is a substitute carbohydrate store for humans and

animals. It is found in all cells; mostly in liver and

muscle tissue. It is found in the form of scattered

particles in the cytoplasm.

Glycogen is a homopolysaccharide made of glucose

units. When hydrolyzed, it only gives glucose units. It is

similar to a multi-branched and large-molecule

amylopectin.

Glycogen

The intermolecular connections are similar to amylopectin.

α;14 glycosidic linkages and α;16 glycosidic linkages

at branching points.

It is very resistant to hot alkalines. When dissolved in water,

give colloidal solutions.

When hydrolyzed with dilute acids, it is separated into

glucose units. When hydrolyzed by the action of α-amylase

and β-amylase, a mixture of maltose and dextrins occur.

Glycogen

The glycogen breaks down into glucose and the addition of glucose to the glycogen molecule continues to change direction, depending on the requirements of the organism. As with many polysaccharides, the molecular weight is not constant. It changes constantly.

It is red-brown with iodineand sometimes purple-violet.

Glycogen

Glucogenin

It is one of the most important molecule of plants and constitutes the supporting structure of plant tissues.

The most common organic compounds in nature. It's found in abundance on paper.

It is a straight chain polysaccharide composed of glucose units.

Unlike starch and glycogen, glucose molecules in cellulose are linked by β;1→4 glycosidic bonds.

Cellulose

Its disaccharide unit is cellobiose.

There is no nutritional value for humans. Only ruminants

can benefit.• The microorganisms found in the digestive tract of ruminants

secrete cellulase, an enzyme that breaks down the cellulose.

Cellulose can be used by ruminants in this way.

It is insoluble in water. They are dissolved in dense HCl,

H2SO4, HNO3 and inn ammonia solutions of copper salts.

No characteristic color response with iodine.

Cellulose

Source: Wiki

GlycogenStarchCellulose

It is a homopolysaccharide established from fructose

units. The fructose units are in a straight chain and

linked by β;1→2 glycosidic bonds.

It is found in the roots of various plants; abundant in the

root of plants, artichoke, onion and garlic.

It is used in food industry and medical field.

İnulin

Chitin is a long-chain polymer of an N-acetylglucosamine, a derivative of glucose.

It is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods such as crustaceans (e.g., crabs, lobsters and shrimps) and insects, In terms of function, it may be compared to the protein keratin.

Chitin has proved versatile for several medicinal, industrial and biotechnological purposes.

Chitin

Dextran is a complex branched glucan (polysaccharide made

of many glucose molecules) composed of chains of varying

lengths (from 3 to 2000 kilodaltons). • It is used medicinally as an antithrombotic (antiplatelet), to reduce

blood viscosity, and as a volume expander in hypovolaemia.

The straight chain consists of α;16 glycosidic linkages

between glucose molecules, while branches begin from

α;13 linkages.

Dextran is synthesized from sucrose by certain lactic acid

bacteria, the best-known being Leuconostoc mesenteroides

and Streptococcus mutans. Dental plaque is rich in dextrans.

Other Homopolysaccharides

If the polysaccharides molecules are formed by different

kinds of monosaccharides, they are

considered heteropolysaccharides.• Hyaluronic acid, formed by thousands of alternative units of N-

acetyl glucosamine and glucuronic acid, is an example of

heteropolysaccharide.

• One of the important groups forms mucopolysaccharides. It is

a biologically important substance, which contains amino

sugars and uronic acids as basic substances.

Heteropolysaccharides

Mucopolysaccharides (Glycosaminoglycans) are found

in the tissues of which they belong, partly in the form of

proteins and as mucoproteins.

Due to the uronic acids and acid characters in the

structure, they are called acid mucopolysaccharides. Its

main examples are hyaluronic acid, heparin and

chondroitin sulfate, which are common in animal

tissues. N-acetyl-hexosamine is found in the structure

of all.

Heteropolysaccharides

The glycosaminoglycans are a family of linear polymers composed of repeating disaccharide units.

They are unique to animals and bacteria and are not found in plants.

One of the two monosaccharides is always either N-acetylglucosamine or N-acetylgalactosamine; the other is in most cases a uronic acid, usually D-glucuronic or L-iduronic acid.

Heteropolysaccharides

The glycosaminoglycan hyaluronan (hyaluronic acid)

contains alternating residues of D-glucuronic acid and

N-acetylglucosamine.

It forms clear, highly viscous solutions that serve as

lubricants in the synovial fluid of joints and give the

vitreous humor of the vertebrate eye its jellylike

consistency.

Hyaluronic Acid

Hyaluronan is also a component of the extracellular matrix

of cartilage and tendons, to which it contributes tensile

strength and elasticity as a result of its strong noncovalent

interactions with other components of the matrix.

Hyaluronidase, an enzyme secreted by some pathogenic

bacteria, can hydrolyze the glycosidic linkages of

hyaluronan, rendering tissues more susceptible to bacterial

invasion. • In many animal species, a similar enzyme in sperm hydrolyzes an

outer glycosaminoglycan coat around the ovum, allowing sperm

penetration.

Hyaluronic Acid

They are very similar with Hyaluronic acid.

There are 3 types.• Chondroitin sulfate A

• Chondroitin sulfate B

• Chondroitin sulfate C

They are usually attached to proteins.

Chondroitin sulfate A and Chondroitin sulfate C are similar to each other.

Chondroitin Sulphates

It occurs by repeating glucuronic acid and N-acetyl-

galactosamine units.

In both, N-acetyl-galactosamines carry sulphate.

The difference between them is due to the difference in

the carbon atom to which the sulphates belong. The

monosaccharide units are linked to each other by

repeating one β;1→3, one β;1→4 glycosidic bond.

Chondroitin Sulphates

Chondroitin sulphate B contains iduronic acid rather

than glucuronic acid.

It is the basic structure of animal tissues.• Chondroitin sulphate A is found in cartilage, adult bones and

cornea.

• Chondroitin sulfate B is found in the skin, heart valves and

tendons.

• Chondroitin sulfate C is found in cartilage and tendon.

Chondroitin Sulphates

They are polysaccharides present in erythrocytes,

secretions such as saliva and stomach ulcer, also in

cystic fluids and in the feces of newborn offspring.. • In a small proportion milk is found in sperm and urine.

They are usually formed by combining one of the

glucosamine or galactosamine and the simple sugar

repeatedly with β;1→ 3 and β;1 →4 glycosidic bonds.

Blood Group Antigens

Sometimes glucosamine and galactosamine can be found

together. This structure is mostly found in sialic acid and

fucose.

When they bind to proteins, erythrocyte antigens (A,

B, O, Rh, etc.) are forme as well as differentiate blood

groups.

Blood Group Antigens

Source: Biosiva

Heparin is a heteropolysaccharide that is formed by

conjugation of glucuronic acid and glucosamine-2,4-

SO4 by α;1→3 and α;1→4 glycosidic bonds.

It is an anti-clotting substance, that is, anticoagulant.

It is found in the liver, lungs, thymus, spleen and blood.

Heparin

It is a plant-derived heteropolysaccharide (Acacia

senegal).

When hydrolyzed, it gives galactose, arabinose or xylose

and sometimes a mixture of them. Other than these,

rhamnose and glucuronic acid are found.

Widely used in the preparation of pharmaceuticals, in

confectionery and offset printing techniques.

Gum arabic

They are very common in plants in the country.

Especially in citrus fruits, apples, beets and carrots are

associated with cellulosic cell walls.

When hydrolyzed with hot dilute acid, it is separated

into pectic acid and methanol.

Pectines

Which of the following monosaccharides is a ketohexose?

a- Glucose

b- Fructose

c- Mannose

d- Ribose

e- Sedoheptulose

Question 1Answer : B

Which of the following monosaccharide pairs will cause

maltose disaccharides to occur?

a- Glucose + Fructose

b- Glucose + Galactose

c- Glucose + Glucose

d- Glucosamine + Glucosamine

e-Galactose + Fructose

Answer: C

Question 2

Enzymes that perform hydrolysis of starch are called ...

a- Glycosidase

b- Amylase

c- Lipase

d- sukraz

e- Pepsin

Question 3Answer: B

Ası T (1999). Tablolarla Biyokimya I ve II, Nobel Tıp Kitapları Dağıtım,

Ankara.

Engelking LR (2014). Textbook of Veterinary Physiological Chemistry. 3rd

Edition. Academic Press.

Lehninger AL, Nelson Dl, Cox MM (2012). Principles of Biochemistry, 6th

Edition, United States of America.

Rodwell V, Bender D, Botham KM, Kennelly PJ, Weil PA (2015). Harpers

Illustrated Biochemistry. 30th Edition. McGraw-Hill Education

Sözbilir Bayşu N, Bayşu N (2008). Biyokimya, Güneş Kitabevi.

References

Lipids