Transcript
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.
top related