Biochemistry
Sixth Edition
Berg • Tymoczko • Stryer
Chapter 11:
Carbohydrates
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Carbohydrates
Common terms
Monosaccharides: glucose, fructose, mannose, etc.
Disaccharides: maltose, cellibiose, sucrose, lactose
Polysaccharides: starch, glycogen, chitin,
glycosaminoglycans
Aldoses, ketoses
Pentoses, hexoses
Pyranose, furanose
Anomeric carbon atom, anomers, a, b
D,L isomers, epimers, penultimate carbon
Glycosidic bond, hemiacetal, acetal
Mutarotation
Reducing sugar
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Trioses (three carbons)
* Know
*
*
aldose
aldose
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ketose
Adlose family
*
Aldose family
* Know
*
*
*
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*
Ketose family
*
Ketose family
* Know
*
*
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D-Stereochemistry of Glucose
Convention for
the Fischer
projection:
CHO
H C OH
HO C H
Carbonyl (#1C) is
at the top.
OH to right = "D"
OH to left = "L"
H C OH
H C OH
Penultimate C
CH2 -OH
Glucose is assigned the D stereochemistry
because the penultimate carbon atom is D.
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Hemiacetal formation
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Pyranose and Furanose forms
Hemiacetal,
Haworth
structure
Hemiketal,
Haworth
structure
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Haworth Structure of Glucose
Draw Fischer, rotate 90o,
then form the hemiacetal
a-anomer
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b-anomer
Haworth Structure of Fructose
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Ribose and Deoxyribse
Haworth structures
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Mutarotation of Fructose
Open
chain
form
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Mutarotation of Glucose
b-D-glucofuranose
~0.5%
a-D-glucofuranose
~0.5%
Open
chain
Form
~0.003%
a-D-glucopyranose
36%, aD = 112o
b-D-glucopyranose
63%, aD = 18.7o
Observed rotation = 52.7o
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Glycosidic
bond (acetal)
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Three glucose residues
The connections (gycosidic bonds) are (a 1-4)
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Lobry de Bruyn-Alberda von
Eckenstein rearrangement
enediol
H-O-
HC=O
CH-OH
CHO
H C OH
C OH
HO C H
HO C H
Reaction
of a sugar
in NaOH.
HO C H
HO C H
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
CH2 -OH
CH2 -OH
CH2 -OH
mannose
glucose
CH2-OH
C O
HO C H
H C OH
H C OH
fructose from CH -OH
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Methylation of Glucose
Converting a hemiacetal to an acetal.
HO-CH2
HO-CH2
O
OH
OH
HO
O
CH3OH
+
H
OCH3
OH
HO
OH
OH
Glycosidic bond
( an acetal)
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Methylation of Glucose
Exhaustive methylation forms one
glycocidic bond and the rest are ethers.
HO-CH2
CH3O-CH2
O
OH
HO
OH
O
excess
OH
CH3I
CH3O-CH2
CH3O
OCH3
OCH3
OCH3
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O
HOH
H+
CH3O
OH
OCH3
OCH3
Sugar Derivatives
Also, oxidized or reduced or
phosphorylated or amino sugars
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Sugar Oxidation at C-1
Gluconic
acid
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Sugar Oxidation at C-6
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Sugar Phosphates
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N-Acetylmuramic acid
N-acetylglucosamine + lactate,
A component of bacterial cell wall.
HO-CH 2
O
O
HO
OH
NH-C-CH 3
CH3-CH-COOH
O
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N-Acetylneuraminic acid
N-acetylmannosamine + PEP
COO-
HOH
..
HO-CH2
C-O-PO3=
HO-CH2
O
OH NH
OH
O
CH2
OH
OH NH CHO
HO
C-CH3
H-O C-O-PO3=
HO-CH2
CH2
OH
HO
COO-
OH NH CH
OH
HO
C-CH3
C-CH3
O
O
Pi
COO-
NH
CH3-C
O
CHOH
CHOH
COOOH
O
CH2
OH
..
OH NH CH
OH
HO
OH
CH 2OH
C=O
HO-CH2
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C-CH3
O
Common disaccharides
The anomeric OH in 1, 2, & 3 may
be a or b, but sucrose may not.
1. Maltose:
a-D-glucopyranosyl-(14)-a-D-glucopyranose
2. Cellibiose:
b-D-glucopyranosyl-(14)-a-D-glucopyranose
3. Lactose:
b-D-galactopyranosyl-(14)-a-D-glucopyranose
4. Sucrose:
a-D-glucopyranosyl-(12)-b-D-fructofuranoside
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Maltose, a disaccharide
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Other disaccharides
Cellibiosefrom
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Common Homopolysaccharides
1. Amylose (linear starch)
An a-(14)-D-glucose polymer
2. Cellulose (linear)
A b-(14)-D-glucose polymer
3. Amylopectin (branched starch)
An a-(14)-D-glucose polymer branched a-(16)
4. Glycogen (branched)
An a-(14)-D-glucose polymer branched a-(16)
5. Chitin (linear)
An b-(14)-D-N-acetylglucosamine polymer
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Glucopolysaccharides
Homopolysaccharides
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A 1-6 branch point
This branch occurs in glycogen and amylopectin.
However, glycogen is more highly branched.
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A high energy glucose carrier
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Heteropolysaccharides
Glycosaminoglycans
(disaccharide repeating units)
Chondroitin-6-sulfate:
-D-glucuronic acid-(b 13)-N-acetyl-Dgalactosamine-6-sulfate-(b 14)Keratan sulfate:
-D-galactose-(b 14)-N-acetyl-D-glucosamine6-sulfate-(b 13)-Downloaded from
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Heteropolysaccharides
Glycosaminoglycans
(disaccharide repeating units)
Dermatan sulfate:
-L-iduronic acid-(b 13)-N-acetyl-Dgalactosamine-4-sulfate-(b 14)Hyaluronic acid:
-D-glucuronic acid-(b 13)-N-acetyl-Dglucosamine-(b
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A Proteoglycan
A glycoconjugate:
(polysaccharide
linked to a protein
or peptide)
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Proteogycan
Electron
micrograph
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Complex Carbohydrates
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L-Fucose
CHO
L-fucose
is 6deoxy-Lgalactose
HO C H
H C OH
H C OH
HO C H
CH3
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Linkages in Glycoproteins
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N-Linked Carbohydrate
High
mannose
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N-Linked Carbohydrate
Complex
carbohydrate
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Dolichol phosphate
(isoprenoid)
This is the endoplasmic reticulum membrane anchor
on which the core carbohydrate for a glycoprotein is
synthesized. It is then modified in a Golgi body.
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From Golgi to Lysosome
Mannose-6-P is a
marker that directs
some hydrolytic
proteins from a Golgi
body to a lysosome
where glycolipids and
glycosaminoglycans
are degraded.
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Hydrolysis of the
N-acetylglucosamine
to leave a Mannose-6-P
residue.
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Review - Glycoconjugates
1. Proteoglycans (glycosaminoglycans + protein).
Mostly carbohydrate (~85%), e.g. cartilage
2. Glycoproteins (most 1-10% carbohydrate).
N and O linked complex carbohydrates
e.g. receptors
3. Peptidoglycans (carbohydrate + small peptide).
e.g. bacterial cell wall
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Proteoglycan
Sketch
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Peptidoglycan
Bacterial cell wall (murein): A long linear polymer
of:
-N-acetyl-D-glucosamine-(b 14) -N-acetylMuramic acid-(b 14)A tetrapeptide is attached through the carboxyl of
the lactate moiety of muramic acid.
Lactate-CO-L-Ala-D-isoGlu-L-Lys-D-Ala-
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Peptidoglycan
Bacterial cell wall:
Lactate-CO-L-Ala-D-isoGlu-L-Lys-D-AlaIn gram (+) bacteria crosslinks are formed by a
pentaglycine bridge from the D-Ala residue above
to the L-Lys in another peptide. (Outer surface is
carbohydrate)
In gram (-) bacteria crosslinks are formed by a direct
link from the D-Ala residue above to the L-Lys in
another peptide. (Outer surface is cell membrane)
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Gram Positive (+) Cell Wall
Up to 20
layers of
peptideglycan
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Gram Negative (-) Cell Wall
Monolayer of
peptideglycan
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Biochemistry
Sixth Edition
Berg • Tymoczko • Stryer
End of Chapter 11
Copyright
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from © 2007 by W. H. Freeman and Company
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