Bio 131 INT
2016-2017
Véronique ROSSI
Vé[email protected]
Carbohydrates
I - Introduction
II - Monosaccharides
III - Chemical reactivity
IV- Analysis and separation of saccharides: techniques
V - Dissacharides
VI- Polysaccharides
VII - Glycoconjugates
1
References
 Book
Principles of Biochemistry D. Voet, J.G. Voet, C. W. Pratt
Chapter 8
 Websites
General biochemistry
http://www.biologymad.com/master.html?http://www.biologymad.com/Biochemistry
/biochemistry.htm
Carbohydrates
http://www.biologie.uni-hamburg.de/b-online/e16/16.htm
CHAMILO – Bio101 French Folder / Documents/Parcours International
2
Bio 131 INT
2016-2017
Carbohydrates
I - Introduction
3
I/1 - Main biological roles of sugars
Energy sources
Structural materials
Cellular metabolism
Storage or energy sources
sucrose
starch
glycogen
glucose
DNA
or
RNA
Red blood cells
Desoxyribose ABO blood
group antigens
Ribose
Plants and bacteria walls
cellulose
peptidoglycan
energy
4
I/2 - General definitions
 Carbohydrates, saccharides, sugars
Greek: sakcharon, sugar
 Cn(H20)n, n ≥ 3
 Characteristics
1. complexity
2. chemical formula
3. spatial structure
5
I/3 - Complexity
Saccharides
Carbohydrates
Building blocks
OSES
Monosaccharides
Simple sugars
(can not be hydrolysed)
6
OSES
Monosaccharides
Simple sugars
(can not be hydrolysed)
= structural units of saccharides
Glucose (cyclic form)
7
I/3 - Complexity
Saccharides
Carbohydrates
Building blocks
OSES
Monosaccharides
Simple sugars
(can not be hydrolysed)
Polymers
OSIDES
Polysaccharides
Glycans/glycosides
(can be hydrolysed)
HOLOSIDES
(hydrolysis
oses)
8
HOLOSIDES
Polysaccharides
(can be hydrolysed)
Hydrolysis (at glycosidic linkages)
Structure of Glycogen
9
I/3 - Complexity
Saccharides
Carbohydrates
Building blocks
OSES
Monosaccharides
Simple sugars
(can not be hydrolysed)
Polymers
OSIDES
Polysaccharides
Glycans/glycosides
(can be hydrolysed)
HOLOSIDES
(hydrolysis
oses)
OLIGOHOLOSIDES
Oligosaccharides, oligosides
2 to 10 oses
POLYHOLOSIDES
Polysaccharides, polyhosides
> 10 oses
10
I/3 - Complexity
Saccharides
Carbohydrates
Building blocks
Polymers
OSIDES
Polysaccharides
Glycans/glycosides
(can be hydrolysed)
OSES
Monosaccharides
Simple sugars
(can not be hydrolysed)
HOLOSIDES
(hydrolysis
oses)
OLIGOHOLOSIDES
Oligosaccharides, oligosides
2 to 10 oses
POLYHOLOSIDES
Polysaccharides, polyhosides
> 10 oses
HOMOPOLYOSIDES
Homopolysaccharides
(oses =)
HETEROPOLYOSIDES
Heteropolysaccharides
(oses #)
11
HOMOPOLYSACCHARIDES
(oses =)
Amylose
n
Cellulose
n
Amylopectin
n
12
HETEROPOLYSACCHARIDES
(oses #)
Glucomannan
(glucose and mannose)
n
n
Arabinogalactan
(arabinose and galactose)
13
I/3 - Complexity
Saccharides
Carbohydrates
Building blocks
Polymers
OSIDES
Polysaccharides
Glycans/glycosides
(can be hydrolysed)
OSES
Monosaccharides
Simple sugars
(can not be hydrolysed)
HOLOSIDES
(hydrolysis
oses)
OLIGOHOLOSIDES
Oligosaccharides, oligosides
2 to 10 oses
HETEROSIDES
(hydrolysis
oses + other molecules
POLYHOLOSIDES
Polysaccharides, polyhosides
> 10 oses
HOMOPOLYOSIDES
Homopolysaccharides
(oses =)
HETEROPOLYOSIDES
Heteropolysaccharides
(oses #)
14
Oligosaccharides chains
(glycans)
HETEROSIDES
(hydrolysis: oses + other chemical species)
Glycoconjugates
Protein chain
Ex: glycoprotein
15
I/4 - Chemical formula
collective formula Cn(H2O)n
 Several hydroxyl groups
Primary alcohol R1 – CH2- OH
R2
*
Secondary alcohol R1 – CH
OH
 asymmetric C-atom
2 possible configurations
 One carbonyl group:
• aldehyde
O
R1 – C
H
O
• ketone
R1 – C
R2
16
I/5 - Classification
 According to the chemical nature of the carbonyl group
Aldehyde  aldose
ketone  ketose
 According to the number of C-atoms
Cn (H2O)n
n = 3  triose
n = 4  tetrose
n = 5  pentose
n = 6  hexose
n = 7  heptoses
 According to the stereochemistry of the asymmetric carbons
D- or L- stereoisomers
17
Summary
Carbohydrates are classified and named according to :
The complexity of their formula
The chemical nature of the carbonyl group
The number of their C-atoms
The configuration of the asymmetric C
Examples:
Aldose with 3 C-atoms and D-isomer
D - aldotriose
Ketose with 6 C-atoms and L-isomer
L- ketohexose
18
Bio 131 INT
2015-2016
Carbohydrates
II – Monosaccharides or simple sugars
Formula and structures
19
II/1 – Trioses
Aldose
ketose
Iary alcohol
aldehyde
IIary alcohol
ketone
*
Iary alcohol
Iary alcohol
D-glyceraldehyde
dihydroxyacetone
(D, the- OH is on the right)
 * Asymmetric center
20
II/2 – Chirality
Chiral object:
Not identical to its mirror image (it can not be superposed to it)
Stereoisomers
(spatial isomers)
Molecule with one chiral center:
the molecule and its mirror image are called enantiomers
identical chemical and physical properties
except for their ability to rotate plane polarized light
Molecules with several chiral centers:
the molecules are called diastereoisomers
(ex : aldotetroses, not mirror images of each others)
21
II/3 - Spatial isomers/optical isomers
Enantiomerism # specific optical rotation
 Each enantiomer have the ability to rotate plane polarized light by equal amounts but
in opposite direction : + or A positive value (+) means dextrorotary rotation : deviation to the right
A negative value (-) means levorotatory rotation : deviation to the left
Sign of the specific rotation (experimental number, measured with a polarimeter)
! ≠ the D or L configuration (spatial assignment in Fisher projection)
D-glyceraldehyde
(+)
L-glyceraldehyde
(-)
Racemic mixture
(equal amounts of each enantiomer)
Naturally occuring fructose is D (-)
Naturally occuring glucose is D (+)
22
II/4 - D or L configuration of glyceraldehyde
The assigment of D or L is made according to the Fischer convention
*
*
D-glyceraldehyde
(-OH on the right)
L-glyceraldehyde
(-OH on the left)
Enantiomers
D-sugars are biologically much more abundant than L-sugars
23
E. Fischer: 1902 Nobel Prize for chemistry
II/5 - Numbering of the C-atoms
1
2
3
D-aldotriose
D-Glyceraldehyde
1
2
3
Ketotriose
Dihydroxyacetone
24
II/6 - The D-aldoses family
1
1
Addition of one Catom
2
3
2
3
D-Glyceraldehyde
1
H
2
OH
HO
2
3
3
4
4
D-erythrose
H
D-threose
Diastereoisomers (≠ Enantiomers)
25
II/6 - The D (L) -aldoses family
D (L)-aldoses have the same absolute configuration at the asymmetric
center farthest from their aldehyde group as does D- (L-) glyceraldehyde
-OH on the right (on the left) in the Fischer projection
26
II/6 - Number of stereoisomers
 All the C-atoms substituted with IIary alcohol function are chiral centers
C-chain length
number of stereosiomers
n C* => 2 n stereoisomeres
example: aldohexose n C* = 4
24 =
2x2x2x2
= 16 possible stereoisomers
8 are D-sugars
8 are L-sugars
27
II/6 - The D-aldoses family
diastereoisomers
epimers
2
2
4
4
-OH on the right
epimers
 Epimers differ only by the configuration around one C-atom
28
II/7 - The D-ketoses family
1
Addition of one C-atom
1
+1C
2
3
ketotriose
dihydroxyacetone
2
3
4
ketotetrose
D-erythrulose
Asymmetric C-atom
29
II/7 - The D-ketoses family
epimers
-OH on the right
diastereoisomers
30
II/8 - Stereochemistry of monosaccharides
Stereoisomers: molecules with the same sequence of bonded atoms but a different
orientation of these atoms in space
Enantiomers: two molecules that are mirror images of each other
Diastereoisomers: stereoisomers which are not mirror images of each other
Epimers:
diastereoisomers that differ only by the configuration around one C-atom
Epimers with
respect to C2
Enantiomers
Diastereoisomers
Anomers :
two molecules that differ in the configuration at the anomeric carbon
31
when a monosaccharide cyclizes: anomer α or β