chemistry of...

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CHEMISTRY OF CARBOHYDRATES

Glyceraldehyde: (Glycerose)= Reference Sugar= Simplest

carbohydrate.

The parent compound of all carbohydrates is Glyceraldehyde

(Glycerose) is an aldo-triose (aldo- means contains an aldehyde

group CHO (H-C= O) as the functional carbonyl group at carbon 1

and triose means a sugar containing 3 carbon atoms).

Dihydroxyacetone phosphate:

Dihydroxyacetone phosphate (DHA) is the structural isomer of

glyceraldehyde. It is a ketotriose (Keto means contains a keto

group (C=O) as a functional carbonyl group at carbon 2 and triose

means a sugar containing 3 carbon atoms).This is an example of

aldose –ketose isomerism.

The above chemical structures represent the open chain (straight chain or

Fischer projection formula of Trioses (mono-saccharides containing 3

carbon atoms).

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Open chain(straight chain or Fischer projection formula of

Pentoses (monosaccharides containing 5 carbon atoms):

The above chemical structures represent the open chain (straight

chain or Fischer- projection formula of pentoses( monosaccharides

that contain 5 carbon atoms):

D-Deoxyribose is the de-oxy sugar of D-ribose. (removal of

oxygen at carbon 2.

D-Xylose is the epimer of D-ribose (configuration of OH at

carbon 3).

D- Ribulose is the structural isomer of D-Ribose. (Aldose (D-

Ribose) and –ketose (D-Ribulose) isomers).

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Definitions:

1. Structural isomers:

Structural isomers are compounds that have the same molecular formula (empirical formula such as Glucose and Fructose C

6H

12 O

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and differ in their structural formula (the bond connections or their order differs carbon 2 in fructose is a keto group and carbon 1 in glucose is an aldehyde group). This is an example of aldose –ketose isomerism. ( Glucose is the Aldose and Fructose is the Ketose). ose means sugar.

The above chemical structures represent the open chain (straight chain or Fischer projection formula of hexoses (monosaccharides that contain 6 carbon atoms)

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2. Epimers:

These are isomers that differ in position of OH groups attached to

a single C atom other than the functional carbonyl carbon which is

the anomeric carbon in the ring form (C 1 in glucose and C 2 in

fructose). This is an example of stereoisomerism.

The above chemical structures represent the open chain (straight

chain or Fischer projection formula of hexoses (monosaccharides

that contain 6 carbon atoms).

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Enantiomers (D-and L- isomerism)

When the OH group attached to the C atom which is next to the last (Terminal C atom = terminal primary alcoholic group) CH

2OH

group is on the right, the sugar is described as D-sugar. If the OH group is on the left, it is described as L-sugar.

Glyceraldehyde that has one asymmetric carbon atom so according to the rule number of isomers = 2n , where, n= number of asymmetric carbon atoms (Chiral centers) it has 2 optically active forms L and its mirror image D forms (enantiomers). The majority of sugars in humans are D-sugars.

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Cyclic structure of sugars: (Ring structure of sugars):

Pyran = 6 membered ring.

Furan= 5 membered ring.

Ring structure of sugars are hemiacetals

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Open chain(Fischer projection) formula of D-ribose and

Haworth projection formula of ring structures of

α-D-ribose (α-D-ribofuranose) and

β-D-ribose (β-D-ribofuranose)

Haworth formula Haworth formula

Of ring structure Open chain

(Fischer projection formula)

______________________________________________________

______________________________________________________

α- D-Ribofuranose β- D-Ribofuranose

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Haworth Projection formula of ring structure of:

α-D- glucose (α-D-glucopyranose) and

β- D-glucose (β-D-glucopyranose)

______________________________________________________

TO DRAW HAWORTH FORMUA OF THE RING STRUCTURE:

1. All the –OH groups on the right side in the old ring structure

are written downwards in Haworth formula.

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2. All the –OH groups on the left side in the old ring structure

are written upwards in Haworth formula.

3. These rules are reversed at CH2-OH groups e.g., the last

carbon atom of glucose that is attached to oxygen i.e. C4 in

furanose and C5 in pyranose.


β-D- fructofuranose


α-D- fructofuranose

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α-D- fructopyranose.

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Derived monosaccharides

1. Amino sugars:

Fischer projection formula of amino sugars

2. Deoxysugars:

Haworth projection formula of Deoxy sugars

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3. Sugar acids:

Fischer projection( open chain) formulaof

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Sugar alcohols:

Fischer projection (open chain)formula of

Haworth projection formula of Myo-inositol

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Sugar esters:

Haworth projection formulaof sugar esters (sugar

phosphates):

Reducing Disaccharides:

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1. Maltose:

2-Galactose (sugar of milk):

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Glycosaminoglycans are long, in most cases un-branched, heteropolysaccharide chains generally composed of a repeating disaccharide unit [acidic sugar-amino sugar].

The amino sugar is either D-glucosamine or D-galactosamine in which the amino group is usually acetylated, thus eliminating its positive charge.

The amino sugar may also be sulfated on carbon 4 or 6, or on a non-acetylated nitrogen. The acidic sugar is either D-glucuronic acid or its

carbon 5 epimer, L-iduronic acid.

Acid sugars:

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Aminosugars

Examples of glycosaminoglycans

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صورة مكبرة للصورة الصغيرة اللى فوقها بتاعة

HEPARIN and HEPARAN sulfate

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االختصارات:

GlcUA : Glucuronic acid.

IdUA: Iduronic acid.

GlcNAC: N-acetyl Glucosamine

GalNAC: N-acetyl Galactosamine.

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Chemistry of proteins

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Amino acids with basic side chains

Associate Prof. Dr. Hassan Fayed

chemistry of...

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