[1] Carbohydrate Chemistry

Monosaccharide

Oligosaccharide

Polysaccharide

Classification of Carbohydrates

Carbohyrates

Compounds composed of C, H, O

Carbohydrates

Are the most abundant compounds in nature

Aldose

CH double bond O

Ketose

C double bond O

Carbohydrates

Source of Energy, esp for brain cells and RBC

Carbohydrates

Intermediates in the biosynthesis of other basic biochemical entities (fats and CHON)

Carbohydrates

Associated with other entities such as glycosides, vitamins, and antibiotics

Carbohydrates

Forms the structural tissues in plants and microoganisms

Carbihydrates

Participate in biological transport, cell-cell recognition, activation of growth factors, modulation of immune system

Homopolysaccharides

have only 1 type of sugar

Heteropolysaccharides

Have different types of sugarsMon

mosaccharides

aka simple sugars

monosaccharides

classified either by the # of C atoms or by the nature of functional group aldose or ketose

d-glyceraldehyde

simplest of the aldoses (aldotriose)

dihydroxyacetone

simplest of the ketoses (ketotriose)

glucose

is a polyhydroxyaldehyde

fructose

is a polyhydroxyketone

monosaccharide nomenclature

according to the # of C they contain in their backbone structure + -ose

monosaccharide nomenclature

according to the nature of reactive group (aldehyde/keto group)

3C Triose

Glyceraldehyde, Dihydroxyacetone

4C Tetrose

Eryhtrose, Erythrulose

5C Pentose

Ribose, Ribulose, Xylulose

6C Hexose

Glucose, Galactose, Mannose, Fructose

9C Nonose

Neuraminic Acid (Sialic Acid)Ne

neuraminic acid

aka as sialic acid

aldotriose

has 1 chiral carbon

aldotetrose

has 2 chiral carbons

aldopentose

has 3 chiral carbons

dihydroxyacetone

has no chiral carbon

asymmetric carbon atom

a c atom attached to 4 different groups

asymmetric carbon atom

aka chiral carbon atom

glyceraldehyde

reference sugar for a 3-carbon sugar glycerose

dihydroxyacetone

reference sugar for a 3-carbon ketose

D isomer

-OH is on the right

L isomer

-OH is on the left

diastereoisomer

isomers that are not mirror images of each other

enantiomers

mirror images of each other

optical isomers

are two compounds which contain the same number and kinds of atoms, and bonds (i.e., the connectivity between atoms is the same), and different spatial arrangements of the atoms, but which have non-superimposable mirror images.

Dextrorotatory

(+) to the right

Levorotatory

(-) to the left

polarimetry

measurement of optical activity in chiral molecules using plane polarized light. measures using Polarimeter

Mannose and Galactose

most important epimers of glucose

mannose

epimer of glucose at C2

galactose

epimer of glucose at C4

fructose

belongs to the ketose and is the SWEETEST sugar

pyranose

6-membered o2 containing rings

furanose

5-membered o2 containing rings

hemiacetal

ring structure of an aldose

hemiacetal

formed by a combination of an aldehyde and an alcohol group

hemiketal

ring structure of an alcohol

anomeric carbon

the C about which rotation occurs

hemiacetal

cyclization happens between C1-C5

hemiketal

cyclization happens between C2-C5

fischer projection

straight chain representation

haworth projection

simple ring in perspective conformational representation

fischer projection

-OH on the RIGHT: alpha configuration

-OH on the LEFT: beta configuration

haworth projection

-OH below: alpha

-OH above: beta

Aldose-Ketose isomers

glucose and fructose

reactions of monosaccharides

1. oxosazone formation

2. reduction

3. oxidation

4. action of alkali

5. action of acid

6. glycoside formation

7. ester formation

osazone formation

used for the identification of sugars

osazone formation

consists of reacting the monosaccharide with phenyl hydrazine

d-fructose and d-mannose

give the same needle-shaped osazone crystals as d-glucose

HPLC or Mass spectrometry

used nowadays for the identification of sugars

aldolases

may be oxidized to 3 types of acids: ASU

1. aldonic acids

2. uronic acids

3. saccharic acids

aldonic acids

aldehyde group is converted to a carbonyl group

ex.

glucose to gluconic acid

galactose to galactonic acid

mannose to mannonic acid

uronic acid

aldehyde is left intact and primary alcohol at the other end is oxidized to -COOH

ex.

glucose to glucuronic acid

galactose to galacturonic acid

mannose to mannuronic acid

saccharic acids

oxidation at both ends of monosaccharide

aka glycaric acid

ex.

glucose to gluco saccharic acid

galactose to mucic acid

mannose to mannaric acid

reduction

either done catalytically (suing hydrogen and catalyst) or enzymatically (-OL)

reduction

the resultant product if a polyol or sugar alcohol

sorbitol (glucitol)

glucose

mannitol

mannose

mannitol+sorbitol

fructose

glycerol

glyceraldehyde

actions of strong acids

monosaccharides are normally stable in dilute acids but are dehydrated by strong acids

furfural

d-ribose when heated with concentrated HCL yields __

5-hydroxymethyl furfural

d-glucose when heated with concentrated HCL yieds __

Actions of Alkalis

in mild alkaline conditions enediols are formed

enediols

are highly reactive sugars and are powerful reducing agents

Lobry de Bruyn-Van Ekenstein transformation

interconversion reaction (d-mannose, d-fructose, d-glucose)

caramelization (decomposition) of sugar

caused by strong alkalis

copper sulfate

frequently used as an oxidizing agent and a red precipitate is obtained

fehling’s solution

KOH or NaOH and CuSO4

detection of reducing sugars

benedict’s solution

Na2CO3 and CuSO4

important derivatives of monosaccharides

1. amino sugars

2. deoxy sugars

3. sugar acids

4. sugar alcohols

5. sugar esters

6. glycosides

amino sugars

formed by replacing the -OH (hydroxyl) group (at C2) of monosaccharides by amino group

glucosamine and galactosamine

most common amino sugars

glucosamine

present in heparin, hyaluronic acid, and blood group substances

galactosamine

present in chondroitin of cartilages and tendons

n-acetylglucosamine

amino group condensed with active acetate

n-acetyl mannosamine

a component of glycoproteins and gagngliosides (lipids) of cell membrane

polymer of N-acetyl glucosamine

a component of chitin

n-acetyl galactosamine

a component of chondroitin sulphate

amino sugar acids

are produced by condensation of amino sugar with pyruvic or lactic acid

muramic acid

produced by the condensation of lactic acid with d-glucosamine

n-acetyl neuraminic acid

condensation of pyruvic acid with n-acetyl mannosamine

deoxy sugars

formed by removal of O2 atom from the 2nd C atom

deoxy sugar

found in DNA to prime deoxyribose

2’-deoxy ribose

sugar found in the DNA

6-deoxy-L-mannose (l-rhamnose)

used as a fermentative reagent in bacteriology