CARBOHYDRATES

Carbohydrate - polyhydroxy aldehyde, ketones and their derivatives.

Functions - structure material storage material for carbon and energy.

CONCEPTS OF ISOMERS

Two or more different compounds which contain the same number and types of atoms and the same molecular weights.

 

Projection formula (spatial arrangement to represent 3-dimensional structure):

D-glyceraldehyde (hydroxy group at the highest numbered asymmetric carbon atom is written to the right):

CH2OH

CHO

C HHO

L-glyceraldehyde (hydroxy group at the highest numbered asymmetric carbon atom is written to the left):

D-Erythrose is the mirror image of L-Erythrose.

CH2OH

OH

CHO

CH

Glyceraldehydes: Model compounds of monosaccharides C

O

CH2OH

OHCH HO HC

CH2OH

H H OC

CO

CH2OH

OHCH

HO H

C

CH2OH

H H OC

H C OH

OH

C

H

D-Glyceraldehyde L-Glyceraldehyde

D-Erythrose L-Threose

POLARIMETER

Light

Fixed

Nicol Prism Plane Polarized Light

Cell (Sample)

Analyzer

Nicol Prism

Eye

Dextrorotatory -plane polarized light rotated to clockwise (or to the right)

Levoratatory - plane polarized light rotated to counterclockwise.

FISHER PROJECTION FORM C

O

CH2OH

OHCH

HO

H

HC

OH

OH

CH

HO

H C OH

OH

CH

H C OH

C H

H

HO

H C

CH2OH

O

C C

O

CH2OH

CH

HO

H

HC

OHCH

H C

OH

or

Anomeric Carbon --- The carbon atom which is involved in hemiacetal oracetal formation.

Anomers: Stereoisomers formed when ring is formed (, ).

CO

CH2OH

OHCH

HO

H

HC

OH

OH

CH

HO

HO HC

OH

C H

H C OH

C H

H

HO

H C

CH2OH

O

C C

O

CH2OH

CH

HO

H

HC

OHCH

HC

OH

or

is same side with ring

HAWORTH PROJECTION FORMULAS FOR SUGARS OH

OH

CH

H C OH

C H

H

HO

H C

CH2OH

O

C

OH

O

OH

OHHO

CH2OH

1

23

45

6

- D - Glucopyranose

HOC

O

CH 2 OH

CH

HO

H

HC

OHCH

H C

OH

HO

OH

CH

H C

OH

C H

H

HO

H C

CH 2 OH

O

C

C

O

CH 2 OH

CH

HO

H

HC

OH

CH

H C

OH

OH

CO

CH 2 OH

OHCH

HO

H

HC

OHCH

OHH C

OH

OH

CH

H C OH

C H

H

HO

H C

CH 2 OH

O

C

-D-Glucofuranose (0.5%)

-D-Glucopyranose (35%)

-D-Glucofuranose (0.5%)

-D-Glucopyranose (0.5%)

Aldehydo-D-glucose (0.03%)

HAWORTH PROJECTION FORMULAS FOR SUGARS

MONOSACCHARIDE

Hexoses

1. Glucose (dextrose) --- rotate the polarized light to the right.

OH

OH

CH

H C OH

C H

H

HO

H C

CH2OH

O

C

OH

O

OH

OHHO

CH2OH

1

23

45

6

Most common monosaccharide.

Commercially from starch.

Cereal roots, legumes, animal tissue, and liver.

 

Mutarotation --- The optical changes of glucose in water solution to constant value

20D = +520

 

  - D - glucose D - glucose - D - glucose

20D = 113 20

D = 52 20D = = 19

At equilibrium = 35% of - form and 65% of - form.

Glucose (dextrose)

2. Galactose --- Component of lactose (milk sugar)

-D-Galactopyranose

O

OH

OH

CH2OHHO

OH

3. Fructose (levulsoe) --- Rotation in polarimeter is left

D-Fructose -D-Fructose -D-Fructose

CH2OH

O

CH2OH

C

HO HC

OHCH

H C

OH

O

CH2OH

C

HO HC

OHCH

H C

CH2OHCH2OH

CH

HO

H C OH

C HHO

C

OH

CH2OH

O

or

- D - Fructofuranose - D - Fructofuranose

O

HO

OH

CH2OH

HOCH2 OH

O

HO

OH

HOCH2 CH2OH

OH

O

OH

CH2OH

H

OH

OH

OH

CH2OH

C

HO HC

OHCH

H C

OH

O

OH

CH2OH

CH

H C OH

C H

H

HO

H

C

OH

CH2OH

O

C

Naturally-occurring free form

Fructose (levulsoe)

Disaccharides (anydrides of 2 monosaccharides):

Maltose: 4-0--D-Glucopyranosyl (14) -D-Glucopyranose

O

OH

OHHO

CH2OH

O

OH

OH

CH2OH

O OH

Cellobiose

4-0--D-Glucopyranosyl (14)--D-Glucopyranose O

OH

OHHO

CH2OHO

OH

OH

CH2OH

O

OH

Sucrose

2-0--D-Glucopyranosyl -D-Fructofuranoside O

OH

OHHO

CH2OH

CH2OH

OCH2OH

O

HO

OH

H1

23 4

5

6

Invert Sugar --- when sucrose in solution, the rotation changes from detrorotatory (+66.5) to levorotatory (-19.8). So, sucrose is called “Invert Sugar”. Sucrose has been hydrolyzed into glucose and fructose.

Lactose

Principal sugar in milk O

OH

OH

CH2OHO

OH

OH

CH2OH

O

OH

OH

4-0--D-Galactopyranosyl (14)--D- Glucopyranose

4-0--D-Galactopyranosyl (1->4)--D-Glucopyranose

RELATIVE SWEETNESS OF DIFFERENT SUGARS

Sucrose 100

Glucose 74

Fructose 174

Lactose 16

Invert Sugar 126

Maltose 32

Galactose 32

Raffinose (Galactose + Glucose + Fructose)

6-0--D-Galactopyranosyl (1->6)-2-0--D-Glucopyranosyl (1->2)--D-Fructofuranoside

Oligosaccharide O

OH

OH

CH2OH

OH

CH2OHO

OH

OH

O

OH

CH2OH

O

HO

OH

CH2

O

Melbiose Sucrose Moiety

Stachyose (Galactose + Galactose + Glucose + Fructose)

6-0--D-Galactopyranosyl (16)-6-0--D-Galactopyranosyl (1-> 6) -2-0--D-Glucopyranosyl--D-Fructofuranoside

“Flatulence Factor” O

OH

OH

CH2OH

OH

CH2OH

O

OH

OH

OH

OH

CH2OH

O

HO

OH

CH2

O

O

O

OH

OH

CH2

O

POLYSACCHARIDE

Anhydrides of Monosaccharides Through ether linkages.

Cellulose --- polymer of -D-Glucose (1, 4) linkage.

Repeating cellobiose moiety. O

OH

OH

CH2OH

OH

O OO

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

n

The reserve carbohydrate of plants. Occurs as granules in the cell. Made of amylose and amylopectin.

Amylose --- ploymer of -D- Glucose (14) linkage-straight-chain.

STARCH O

OH

OH

CH2OH

OHO OO

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

O

OH

OH

CH2OH

Amylopectin

Polymer of -D-Glucose (1->4) linkage in addition to -D-Glucose (16) linkage.

The length of linear units in amylopectin is only 25.

-(14) linkage (25) to -(16) linkage.

GLYCOGEN

Animal starch.

- (1 4) linkage and - (1 -> 6) linkage

12 : 1

Polymer of 4-0--D-Galacturonic acid (1 -> 4) & Methylgalacturonate

PECTIN O

OH

OH

OH

O OO

O

OH

OH

O

OH

OH

O

OH

OH

O

OH

OH

O

OH

OH

COOH COOCH3 COOCH3 COOH

DEGREE OF METHYLATION (DM)

The higher the degree of methylation, the higher the temperature at which the gel forms.

 

For gel formation at least 50% of the carboxyl group are methylated. Pectin (about 74 DM) is used in jams. For jellies DM is about 60.

FUNCTIONAL PROPERTIES OF POLYSACCHARIDES (GUMS)

1. Viscosity control

2. Texture control

3. Emulsifying agent

4. Water-binding capacity

5. Stabilizer

CORN SYRUP

Corn Starch

Enzyme

H

Corn Syrup

High Glucose

Maltose

Dextrose

+

Dextrose Equivalent (DE) =Gram of Reducing Sugar

Gram of Total Sugarx 100

The higher the DE, generally the greater the glucose content in corn syrup.

HIGH FRUCTOSE SYRUPS

Generally: Glucose 50%

Fructose 42%

Maltose 1.5%

Isomaltose 1.5%

Higher Saccharides 5.0%

Glucose in Syrup FructoseGlucose Isomerase

CORN SYRUP

  % Dry Weight

Glucose 9 14 43

Maltose 52 12 32

Triose 13 10 3

Tetrose 2 9 5

  High Maltose Syrup

Low DE High DE

Pentose 24 55 12

MODIFIED STARCHES

1.  Pregelatinized Starch --- simple precooked and roll dried to give product that readily disperses in cold water.

2.  Thin-boiling or Acid-modified Starch --- suspending granular starch in a very dilute acid under somewhat below its gelatinization temperature (somewhat mild).

3. Oxidized Starches --- oxidation of starch with alkaline hypochloride to get -coo- at C6.

CARBOHYDRATE DETERMINATION

1. Monosaccharides and Oligosaccharides

A. Enzymatic Method

1. Glucose oxidase

2. Hexokinase

B. Chromatography Method

1. Paper or thin layer chromatography

2. Gas chromatography

3. Liquid column chromatography

 

2. Polysaccharides

Glucose Oxidase System

Glucose Oxidase

D-Glucose + O2 Gluconic Acid + H2O2

  

Peroxidase

H2O2+ 0 - Dianisidine 2 H2O + Oxidized 0-Dianisidine

(Colorless) (Brown) OCH3H3CO

H2N NH2

H3CO OCH3

HN NH

Hexokinase System

NADP+ : (Nicotinamide Adenine Dinucleotide Phosphate)

 

The amount of NADPH formed in this reaction is stoichiometric with the amount of glucose.

NADPH is measured by its absorption at 334 nm.

Hexokinase

Glucose + ATP G - 6 - P + ADP

 

  G - 6 - P DH

G - 6 - P + NADP+ Gluconate - 6 - phosphate + NADPH + H+

QUALITATIVE ANALYSES OF CARBOHYDRATES

Thin Layer chromatography

Silica gel as stationary phase (250 m)

Quantitative by densitomer (time - varies with solvent, generally overnight):

A

B

C

A B

S

Solvent

Rf = AS

For Spot A

Gas Liquid Chromatography

Requirement: compounds must be volatile.

Sugars form Trimethylsilyl Ether: Si SiCl

CH3

CH3

CH3

O

CH3

CH3

CH3

Ether linkage Trimethyl chlorosilane

Liquid Chromatography

Carbohydrate Analysis (Waters Assocs. 840380 Stationary Phase)

Solvent: H2O/CH3CN

Fructose

Glucose

Maltotriose

Maltose

Retention time

POLYSACCHARIDES

Usually, quantitation depends on chemical or enzymatic hydrolyses of them, followed by analysis of the monomers.

Starch

1. Amylose + I- -> Blue complex

Use spectrometer for determining the amylose - iodine blue color - according to spectrophotometric reading.

2. Amylopectin + I- -> Reddish color.