CARBOHYDRATES - PowerPoint PPT Presentation

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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):

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.

Glyceraldehydes: Model compounds of monosaccharides

D-Glyceraldehyde L-Glyceraldehyde

D-Erythrose L-Threose

POLARIMETER

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

Levoratatory - plane polarized light rotated to counterclockwise.

FISHER PROJECTION FORM

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

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

a is same side with ring

HAWORTH PROJECTION FORMULAS FOR SUGARS

a - D - Glucopyranose

OH

H

OH

H

C

H

C

OH

H

C

OH

O

HO

H

HO

C

H

C

O

H

C

H

C

OH

H

C

H

C

OH

CH

OH

CH

OH

2

H

O

C

H

C

OH

HO

H

C

H

C

OH

H

C

OH

CH

OH

2

HO

H

HO

C

H

C

OH

H

C

OH

O

HO

H

C

HO

H

C

O

H

C

H

C

OH

H

C

OH

H

C

CH

OH

2

CH

OH

2

HAWORTH PROJECTION FORMULAS FOR SUGARS

a

-D-Glucopyranose

(35%)

a

-D-Glucofuranose

(0.5%)

Aldehydo-D-glucose

(0.03%)

b

-D-Glucofuranose

b

-D-Glucopyranose

(0.5%)

MONOSACCHARIDE

Hexoses

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

Glucose (dextrose)

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

a20D = +520

a - D - glucose -> D - glucose <-b - D - glucose

a20D = 113 a20D = 52 a20D = = 19

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

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

a-D-Galactopyranose

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

D-Fructose b-D-Fructose a-D-Fructose

Fructose (levulsoe)

CH

OH

CH

OH

2

OH

H

C

O

C

CH

OH

O

2

HO

H

C

OH

H

O

C

OH

H

C

OH

C

OH

H

C

CH

OH

2

H

b - D - Fructofuranose a - D - Fructofuranose

Naturally-occurring free form

Disaccharides (anydrides of 2 monosaccharides):

Maltose: 4-0-a-D-Glucopyranosyl (1->4) a-D-Glucopyranose

Cellobiose

4-0-b-D-Glucopyranosyl (1->4)-b-D-Glucopyranose

Sucrose

2-0-a-D-Glucopyranosyl b-D-Fructofuranoside

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

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

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

RELATIVE SWEETNESS OF DIFFERENT SUGARS

Sucrose 100

Glucose 74

Fructose 174

Lactose 16

Invert Sugar 126

Maltose 32

Galactose 32

Oligosaccharide

Raffinose (Galactose + Glucose + Fructose)

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

Stachyose (Galactose + Galactose + Glucose + Fructose)

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

“Flatulence Factor”

POLYSACCHARIDE

Anhydrides of Monosaccharides Through ether b linkages.

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

Repeating cellobiose moiety.

STARCH

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

Amylose --- ploymer of a-D- Glucose (1->4) linkage-straight-chain.

Amylopectin

Polymer of a-D-Glucose (1->4) linkage in addition to a-D-Glucose (1->6) linkage.

The length of linear units in amylopectin is only 25.

a-(1->4) linkage (25) to a-(1->6) linkage.

GLYCOGEN

Animal starch.

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

12 : 1

PECTIN

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

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

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%

High Maltose Syrup

Low DE

High DE

Pentose

24

55

12

CORN SYRUP

% Dry Weight

Glucose

9

14

43

Maltose

52

12

32

Triose

13

10

3

Tetrose

2

9

5

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.