Transcript Why Carbohydrates - Tehran University of Medical Sciences

DS/ Reducing vs non-reducing
Sucrose
α (D) glucopyranosyl 1
fructofuranoside
Lactose
2
β (D) galactopyranosyl 1
4 glucopyranose
cellulose
Amylose
amylopectin
glycogen
DS that are formed by the linkage of
sugars derivatives
Polysaccharides

Definition and properties:
*They are composed of many
sugar residues.
*All are nonreducing.
PS/Different classification.
1- Branched vs linear polysaccharides.
Example: amylose, inulin, and amylopectin,
glycogen
2- Sturctural vs storage polysaccharides.
Example: Cellulose, pectin and
glycogen, inulin.
3- Homo vs hetero polysaccharides.
Example: Amylon, cellulose and
glycosaminoglycanes.

PS/ linear vs Branched
Amylose
linear
Amylopectin / Glycogen
Branched
Structural vs storage
Other Structural Polysaccharides



Alginates - Ca-binding polymers in algae
Agarose and agaropectin - galactose polymers
Glycosaminoglycans - repeating disaccharides
with amino sugars and negative charges
Dextrans





If you change the main linkages between glucose from
alpha(1,4) to alpha(1,6), you get a new family of
polysaccharides - dextrans
Branches can be (1,2), (1,3), or (1,4)
Dextrans formed by bacteria are components of
dental plaque
Cross-linked dextrans are used as "Sephadex" gels in
column chromatography
These gels are up to 98% water!
PS/Homo vs Heteropolysaccharide
Amylose, inulin, and amylopectin,
glycogen, Cellulose
 Chitin - exoskeletons of crustaceans,
insects and spiders, and cell walls of
fungi
 Similar to cellulose, but C-2s are Nacetyl
 Cellulose strands are parallel, chitins
can be parallel or antiparallel

Hetero PS (Glycosaminoglucans)
(GAG+ peptide)
Glycoproteins vs Proteoglycans
Two main classes of ECM molecules:
a) Glycosaminoglycans
mostly proteoglycans
polysaccharide chains - glycosaminoglycans,
GAGs, covalently bound to proteins
highly hydrated, porous, gels
b) fibrous proteins
(embedded in the above gel)
structural
(collagen, elastin)
strengthen the ECM
adhesive
(fibronectin, laminin)
attach cells
to the appropriate part of ECM
Polysaccharides/ Peptidoglycanes
Gram Negative bacteria
Gram
positive
bacteria
Glycoproteins
Glycolipids Vs Lipopolysaccharides
Glycolipids (Crebroside, Ganglioside)
Relative swetness & Artificial
sweetners
Relative sweetness
of sugar
 Sucrose:
 Glc:
70
 Fru:170
 Mal: 30
 Lac: 16
100
Relative sweetness of
Artificial sweetners
• Cyclamate: 3, 000
• Aspartam: 20, 000
• Saccarin: 40, 000
• Monilin: 400, 000
Different ways for qualitative and quantitative
identification of sugars
Crystal formation(Osazones)
 Furfral and hydroxy furfural reaction with
cyclic alcohol.
 Iodine

Enzymatic
Glucokinase
Hexokinase

Oxidative and reductive reactions: Benedict
Benedict: An assay for sugars
Cu2+
Cu+