“ CHAPTER 5 “ … CARBOHYDRATE… 1. INTRODUCTION -The names come from the term “ hydrate of carbon ” - A class of compounds that contained carbon, hydrogen

“ CHAPTER 5 “

… CARBOHYDRATE…

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INTRODUCTION

-The names come from the term “ hydrate of carbon ”

- A class of compounds that contained carbon, hydrogen and oxygen (C, H, O).

-Also called saccharides the most abundant class of biological molecules on Earth

-Much of it is produced by photosynthetic organisms including bacteria, algae, plants.. (however, all organisms can synthesize carbohydrate)

- FUNCTION act as energy storage molecules (in both animal and plants)

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-Can be described by the number of monomeric units they contain ;-

CLASSIFICATION

MONOSACCHARIDES smallest units of carbohydrate structure

EMPIRICAL FORMULA : (CH2O)n n = (1,2,3,….)

Where n is 3 or greater (n is usually 5 or 6 but can be up to 9)

Basic formula for carbohydrate (i.e. monosaccharide ONLY)

Oligosaccharides and Polysaccharides does not have this empirical since water is eliminated during polymer formation

OLIGOSACCHARIDES polymers of 2 to about 20 monosaccharide residues

DISACCHARIDESthe most common oligosaccharides (consist of 2 linked monosaccharide residues)

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2

3 POLYSACCHARIDESPolymers that contain many

(usually more than 20) monosaccharide residues3

COMMON PROJECTION

D-Tagatose (a ketose)

D-Fructose Fructose

FISCHER

PROJECTION

HAWORTH

PROJECTION

Fructose

Show the configuration of atoms and groups at each carbon atom sugar’s backbone

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GLUCOSE: FISCHER TO HAWORTH PROJECTION

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5.1 CONFORMATIONS OF MONOSACCHARIDES

3 Triose Glyceraldehyde

4 Tetrose Erythrose, Threose

5 Pentose Arabinose, Ribose, Ribulose, Xylose, Xylulose, Lyxose

6 Hexose Allose, Altrose, Fructose, Galactose, Glucose, Gulose, Idose, Mannose, Sorbose, Talose, Tagatose

7 Heptose Sedoheptulose

MONOSACCHARIDE CLASSIFICATION

No. of Carbons Category Name Examples

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3 Triose GlyceraldehydeDihydroxyacetone



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4 Tetrose Erythrose, Threose



D-Erythrose D-Threose

D-Threose

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5 Pentose Arabinose, Ribose, Ribulose, Xylose, Xylulose, Lyxose

D-Ribose D-

Arabinose D-Xylose D-Lyxose

Ribose Deoxyribose

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6 Hexose Allose, Altrose, Fructose, Galactose, Glucose, Gulose, Idose, Mannose, Sorbose, Talose, Tagatose

D-Altrose D-Glucose D-Mannose D-Gulose D-Idose D-Galactose D-Talose

D-Tagatose (a ketose)

D-Fructose Fructose Galactose Mannose

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7 Heptose Sedoheptulose

D-Sedoheptulose

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FAMILIES OF MONOSACCHARIDES

reminder !!

D-Sedoheptulose

D-Erythrose D-Threose

(1) ALDOSES (2) KETOSES

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FAMILIES OF MONOSACCHARIDES

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SEVERAL IMPORTANT CONFIGURATION OF MONOSACCHARIDES

(from cyclization of monosaccharides)

(A) STEREOISOMERISM

3 WAYS (STEREOCHEMICAL FORMS) TO REPRESENT 2 STEREOISOMERS OF GLYCERALDEHYDE

STEREOISOMERS mirror images of each others

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(B) EPIMERS

DEFINITION sugars that differ only in the configuration at only one carbon atom

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(C) MUTAROTATION

DEFINITION the interconversion of α and β anomers in aqueous solution

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(D) ANOMERS

DEFINITION isomeric forms of monosaccharides that differ only in their configuration about the hemiacetal or hemiketal carbon atom.

The hemiacetal (or carbonyl) atom is called the anomeric carbon

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REACTIONS AT THE HYDROXYL GROUPS

(A) CYCLIC ACETAL AND KETAL FORMATION

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5.2 DERIVATIVES OF MONOSACCHARIDES

sugar phosphates

sugar alcohols

sugar acids

deoxy sugars

amino sugars

ascorbic acids

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3

2

5

4

6

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sugar phosphates1


In the synthesis and metabolism of carbohydrates, the intermediates are very often not the sugars themselves but their phosphorylated derivatives (sugar phosphate)

HOW ??

By condensation of phosphoric acid with one of the hydroxyl groups (-OH) of a sugar forms a phosphate ester (e.g. glucose 6-phosphate)

AS A RESULT..

Sugar phosphate relatively stable at neutral pH

bear a negative charge

EFFECT OF SUGAR PHOSPHORYLATION WITHIN CELLS

to trap the sugars inside the cells (most of the cells do not have plasma membrane transporters for phosphorylated sugars)

activates sugars for subsequent chemical transformation20


sugar alcohols2

- e.g. glycerol

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sugar acids (a.k.a acidic sugars)3

- Contain a carboxylate group (confers a negative charge at neutral pH)

Results from formation of an ester linkage between C-1 carboxylate group and the C-5 (also known as the δ carbon) hydroxyl group of D-gluconate

-9-carbon acidic sugars

-A component of many glycoproteins and glycolipids in animals

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deoxy sugars4

- Substitution of –H (hydrogen) for –OH (hydroxyl group)

-Are found in ;-

a) plant polysaccharides

b) complex oligosaccharide components of glycoproteins and glycolipids

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amino sugars5

an –NH2 replaces one of the –OH groups in the parent hexose

-Also called as glucosamine derivatives

-Part of many structural polymers (including those of the bacterial cell wall)

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ascorbic acids6

-derived from D-glucuronate

-is Vitamin C

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CLASSIFICATION








1

2



OLIGOSACCHARIDE

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5.3 DISACCHARIDE AND OTHER GLYCOSIDES

DISACCHARIDES

…can be…

reducing sugar non- reducing sugar

-Have the ability to reduce metal ions such as Cu2+ and Ag+ to insoluble product

-The anomeric carbon of the second monomer is not involved in glycosidic bond

-Have the ability to form the straight chain

e.g.

1. Lactose

2. Glucose

3. Maltose

4. Cellobiose

- Both anomeric carbon atom fixed in glycosidic linkage

each consists of 2 monosaccharides linked by a glycosidic bond

e.g.

1. sucrose

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Disaccharide Descriptions and Components Disaccharide Description Monosaccharides

Componentssucrose common table

sugar glucose + fructose

lactose main sugar in milk galactose + glucose

maltose product of starch hydrolysis

glucose + glucose

trehalose found in fungi glucose + glucose

Sucrose Lactose Maltose

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5.3 DISACCHARIDE AND OTHER GLYCOSIDES

GLYCOSIDES

are all compounds containing the glycosidic bonds

(1) Happen when the anomeric carbon (C1) [of one monomer] can interact with one of several hydroxyl group (-OH) [in

other monomer]

(2) If the anomeric carbon is from glucose, it is called glucosides

(3) Most popular linkage

a) C1 (one monomer) C2 (another monomer)

b) C1 (one monomer) C4 (another monomer)

c) C1 (one monomer) C6 (another monomer)

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CLASSIFICATION








1

2



By definition;-

Is the polymeric compounds of these simple sugars. Also called glycans

e.g.

cellulose, dextrin, glycogen, pectin, fructans,

hemicellulose, lignin, starch

5.4 POLYSACCHARIDES

Glycogen the main storage polysaccharide of animal cell

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TYPES OF POLYSACCHARIDES

(1) HOMOPOLYSACCHARIDES (2) HETEROPOLYSACCHARIDES

(contain only single type of monomer)

Serve as storage form of polysaccharides (e.g. starch n glycogen)

Provide extracellular support for organisms34

EXAMPLE OF POLYSACCHARIDES STARCH

-Structure is identical to glycogen

…BUT…

much lower degree of branching than glycogen…

-2 types of structure ;-

(a) unbranched amylose

(b) branched amylopectin

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Amylose

• consist typically of 200 to 20,000 glucose units which form a helix as a result of the bond angles between the glucose units

Amylose

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Amylopectin• differs from amylose in being highly branched.

• Short side chains of about 30 glucose units are attached with 1α→6 linkages approximately every twenty to thirty glucose units along the chain.

• molecules may contain up to two million glucose units.

Amylopectin

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• These polysaccharides, when hydrolysed will yield the constituent simple sugars.

• The simple sugars can then be bioprocessed to form other products. Some of these products and applications are:

– alternative fuels such as ethanol, methane – starch-based adhesives, agrochemicals (starch encapsulation

agents for pesticides)– cosmetics and toiletries (sorbitol in toothpaste– biodegradable detergents – paper making additives– pharmaceuticals – glucose hydrolysates or their derivatives as fermentation substrate

in order to produce several active compounds (i.e. vitamins, antibiotics and hormones)

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• Inulin from chicory is used as a substrate for pharmaceuticals preparation as it displays beneficial effects on kidney functions

• Starch may also be used for binding, coating and dusting tablets

• Food applications - to stabilise aromas, to remove bitterness from citrus fruits, to trap cholesterol in the process of making lignified butter

• Paints - native starch from potato, maize and wheat can replace up to 25% of the petroleum-based monomer in paint

• Textile - potato starch is used for sizing, cereal starch for printing, dextrins and degraded starches are used for printing

• Water purification - starch-based products acts as coagulants and to aid flocculants in the water treatment industry

• Biodegradable plastics - as adjunct in conventional plastics (6% starch), blended with synthetic polymers (60- 75% starch), as a thermoplastic (75 – 95% starch).

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5.5 GLYCOCONJUGATES

Are the carbohydrate chains (polymers) linked to peptide chain or lipid…..

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Documents

“ CHAPTER 5 “ … CARBOHYDRATE… 1. INTRODUCTION -The names come from the term “ hydrate of carbon ” - A class of compounds that contained carbon, hydrogen