oses and osides
1. DEFINITION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.1. EXAMPLES ..............................................................................................................................2
2. THE DARE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
2.1. NOMENCLATURE BASE........................................................................................................2
2.2. CHIRALITY CENTER: ISOMÉRIE............................................................................................2
2.2.1. Stereoisomer: ............................................... enantiomer ................................................ 3
2.2.2. Able rotatoire...............................................................................................................3
2.3. ABSOLUTE CLASSIFICATION ......................................................................................................4
2.4. REPRESENTATION PROJECTION FISHER ............................................. ............................... 5
2.5. NAMES AND D AND DESCENT OF .......................................... OSES .............................. 6
2.5.1. Aldoses...........................................................................................................................7
2.5.2. Cétoses...........................................................................................................................8
2.6. OF PHYSICAL OSES .............................................. .............................................. 9
2.7. CHEMISTRY OF DARE .............................................. .............................................. 9
2.7.1. Oxidation reaction oses ............................................ ................................................ 10
2.7.2. Reduction reaction oses ............................................. .............................................. 11
2.7.3. Esterification and éthérification............................................................................................11
2.8. PROPERTIES "ABNORMAL" OF DARE ............................................ ......................................... 12
2.8.1. Properties chimiques........................................................................................................12
2.8.2. Physical Property: ............................................ phenomenon mutarotation ...................... 13
2.9. STRUCTURE OF CYCLIC OSES .............................................. .............................................. 13
2.9.1. Hemi-acetalization reaction: .......................................... cyclization ................................. 13
2.9.2. Representation of Haworth ............................................... ................................................ 14
2.9.3. Ring structure: Additional isomerism ............................................. ........................ 16
2.9.4. Conformation ring structures .............................................. ................................... 16
2.9.5. Reactivity anomeric carbon .............................................. ........................................ 17
2.10. DARE BIOLOGICAL INTEREST ............................................. ................................................ 17
2.10.1. Trioses ..........................................................................................................................17
2.10.2. Tétroses........................................................................................................................18
2.10.3. Pentose ........................................................................................................................18
2.10.4. Hexoses........................................................................................................................18
3. THE osides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1. THE oligosides ....................................................................................................................20
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ETS License - Biochemistry 1: Carbohydrates: Summary
3.1.1. The glycoside bond or glycosidic ............................................. ........................................ 20
3.1.2. The diholosides ...............................................................................................................23
3.1.3. Others oligosides........................................................................................................25
3.2. Polysaccharides HOMOGÈNES................................................................................................25
3.2.1. Polysaccharides of réserve..................................................................................................26
3.2.2. Polysaccharides of structure................................................................................................29
3.2.3. Enzymatic hydrolysis of holosides .............................................. ....................................30
3.3. Polysaccharides HETEROGENEOUS ............................................... .............................................. 32
3.4. THE HÉTÉROSIDES..................................................................................................................32
3.4.1. The glycoprotéines...........................................................................................................33
3.4.2. The protéoglycannes.........................................................................................................35
3.4.3. The peptidoglycans .......................................................................................................35
3.4.4. Lectins ....................................................................................................................36
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ETS License - Biochemistry 1: Carbohydrates - 1
Carbohydrates
111 ... Déééfffiiiniiitttiiion
Carbohydrates or called carbohydrates because of their generic formula
base Cn (H2O) n are organic molecules characterized by the presence of membered
carbons bearing hydroxyl groups, and aldehyde or ketone functions,
optionally carboxyl or amine functions. They are divided into monosaccharides and osides.
Dare: also called single or monosaccharide sugar.
- It is non-hydrolyzable and carries most of the time, of 3 to 7 carbon atoms.
- This is a polyol bearing at least two alcohol functions at least one of which is a function
primary alcohol and a reducing carbonyl function, ie:
- Aldehyde (CHO) in this case the venture is an aldose
- Or keto (> C = O) in this case is a dare ketosis
Oside: hydrolysable sugar, it may be:
- Holoside: its hydrolysis releases only oses. We distinguish between:
- Oligoside: association from February to October dare by glycoside bonds
- Polysaccharide: polymer formed from 10 to several thousand monosaccharides
- Homogeneous polysaccharide (or homopolyoside) for a polymer of the same dare
- Mixed polysaccharide (or hétéropolyoside) for a chain of units
different
- Glycoside: its hydrolysis releases sugars and non-carbohydrate compounds (aglycone).
Carbohydrates
dare osides
Aldoses and
derivatives
And ketosis
derivatives
holosides glycosides
oligosaccharides polysaccharides
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ETS License - Biochemistry 1: Carbohydrates - 2
Carbohydrate chains can be fixed chemically or enzymatically on
lipids or proteins: these derivatives are grouped under the term of glycoconjugates
1.1. Examples
The dare is the most common aldohexose: glucose. Its constitution is an isomer
ketohexose: fructose or levulose.
Include disaccharides such as (or disaccharides) maltose, sucrose, lactose.
Starch, glycogen, cellulose are polysaccharides (or polysaccharides).
222 ... Leeesss Ossseeesss
2.1. Basic Nomenclature
The simplest monosaccharides have three carbon atoms:
glyceraldehyde, dihydroxyacetone
The carbon atoms of a monosaccharide are numbered from the most oxidized carbon.
Example: glucose is an aldohexose, fructose a ketohexose.
2.2. Chiral center: isomerism
Chiral object: any object that can not be superimposed on its mirror image is a
chiral object. This definition applies to molecules.
C
C
CH2OH
H O
H OH
CH2OH
C
CH2OH
O
No. Generic Name C
3 trioses aldotrioses, cétotrioses
4 tetroses aldotetroses, cétotétroses
5 pentose aldopentoses, ketopentoses
6 hexoses aldohexoses, ketohexoses
7 heptoses aldoheptoses, cétoheptoses
C
CHOH
H O
CHOH
CHOH
CHOH
CHOH
CH2OH
(1)
(2)
(3)
(4)
(5)
(6)
(7)
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2.2.1. Stereoisomer: enantiomer
In glyceraldehyde molecule C2 carbon (sp3) bearing four different substituents
says is asymmetrical; it is often denoted by C *. Two configurations, but nonsuperposable
images of one another in a mirror are possible: we are dealing with two
stereoisomers, called enantiomers.
The chemical and physical properties of enantiomers are in general identical to
except for a physical property: rotatory power.
When a molecule has several chiral centers, the term diastereomer.
In general for n asymmetric carbons, stereoisomers we 2n and 2 (n-1)
pairs of enantiomers.
2.2.2. Optical rotation
In solution the enantiomeric forms of a molecule bearing an asymmetric carbon
have different optical properties. They are endowed with optical activity:
each of which deviates from the specific manner of a wave polarization plane
monochromatic polarized. The plane of polarization is deviated by an angle equal in value
but absolute reverse.
This property is characterized by the specific rotation:
One of the enantiomers of glyceraldehyde at a concentration of 1g / ml deflects to the right
plane of polarization of a monochromatic beam (λ = 570nm) to 14 ° for a path
optical 10 dm at a temperature of 20 ° C. This enantiomer is dextrorotatory substance,
it is noted (+). The other enantiomer is levorotatory said (-). Both enantiomers are also
called optical isomers.
An equimolar mixture of two enantiomers is optically inactive: it is noted
racemic.
CHO
C *
HO CH2OH
H
CHO
C *
CH2OH OH
H
α λ
[] T = α
l c
t: temperature, λ: wavelength
α: observed rotation l: length of the dm cell
c: concentration of the solution in g / ml
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ETS License - Biochemistry 1: Carbohydrates - 4
Note that the cétotriose (dihydroxyacetone) has no asymmetric carbon and therefore
no optical activity. It comes in only one form and you have to go to a cétotétrose
to have two enantiomeric forms.
History: this is Pasteur, in the years 1850-1860, which separates using two types tongs
of tartaric acid crystals (HO2CCHOHCHOHCO2H), each having properties
different optical rotatory.
1.3. Absolute nomenclature
The convention and the following rules have been defined for an asymmetric carbon:
1 - the four substituents are sorted in an order of priority (a> b> c> d). It aims
the atom along the axis C -> d (Newman projection). If the sequence a, b, c are present in the
direction of clockwise, the configuration of the carbon atom is R (Rectus), in the
otherwise it is S (sinister).
2 - the ranking is in descending order of the atomic number of the atom bound
substituent. In the case of a tie, the atomic number of the neighboring atom is used.
3 - where the atom is involved in multiple bonds, they are considered
"Open" is credited as fictitious substituting its partner in the multiple bond.
In the case of glyceraldehyde, ranking hereby order and accordingly the
Newman projection which is in the following form is the R-configuration:
There is no correlation between the R or S configuration and the nature of the optical rotation,
dextrorotatory (+) or laevorotatory (-).
OH
HOH 2 C CHO
(1)
(3) (2)
axis C-H
back
OH> CHO> CH2OH> H
R Configuration
Newman projection
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ETS License - Biochemistry 1: Carbohydrates - 5
1.4. Fisher projection representation
To saccharides having a longer carbon chain and therefore a larger number of
asymmetric carbons, the use of Fisher spent the representation that is easier to
handling and instead of the absolute nomenclature, the nomenclature D and L.
The molecule is represented in a plane by projection using the following rules:
1 - the asymmetric carbon is placed in the projection plane (the sheet).
2 - the longest carbon chain is vertical and behind the projection plane.
3 - the carbon atom placed on top of the vertical chain is one that is engaged in the
functional group of which the oxidation state is the highest. If the carbon atoms
the ends are in the same oxidation state, who is number 1 in the
International Nomenclature is placed on top.
4 - the other 2 non-carbon substituents of the asymmetric carbon are ahead of plan
projection.
The enantiomer (R) corresponds to the (R) enantiomer of absolute nomenclature, the enantiomer
(Las). For glyceraldehyde, D-glyceraldehyde is dextrorotatory.
Now for a dare higher order, eg aldotétrose. The molecule will
two asymmetric carbon atoms C2 and C3. The individual stereoisomers have one C2 in
R-configuration, the R configuration C3, denoted abbreviated (2R, 3R), its enantiomer (2S, 3S)
then (2R, 3S) and its enantiomer (2S, 3R).
The individual stereoisomers of aldotétrose in Fisher of representation are:
C *
CH2OH
OH
H
CHO CHO
C
CH2OH
H OH
(R) (D)
C *
HO CH2OH
H
CHO
C *
H OH
CHO
CH2OH
(S) (L)
CHO
C
CH2OH
C * H OH
CH2OH
H
OH
CHO
H and OH forward
Fisher projection glyceraldehyde
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The configuration of stereoisomers that are not enantiomers are referred to as
name of diastereoisomers. Configuration of stereoisomers that differ by a single
configuration of an asymmetric carbon are epimers.
- E and E 'are enantiomers, it is the same for T and T'.
- E and E 'are diastereomeric with respect to T and T'.
- E and T are epimers. E and T 'are epimers. This relationship is not transitive (T
T 'are not epimers).
In the absolute classification, the various stereoisomers are designated:
- E (2R, 3R), E '(2S, 3S), T (2S, 3R) and T' (2R, 3S).
The nomenclature D and L refers only to the carbon of the configuration (n-1)
dare, therefore define two series. Series D refers to the Dglycéraldéhyde structure,
that is to say the configuration of the C2 of this molecule. For this aldotétrose
we have: DE, DT and their respective enantiomers THE 'and L-T'.
Abbreviations D and L do not in any case refer to the nature of the optical rotation,
dextrorotatory (+) or laevorotatory (-).
1.5. Nomenclature D and L and filiation oses
The nomenclature D and L oses is a relative nomenclature and by descent. All
sugars will be prefixed by the letters D or L in reference to aldoses configuration
glyceraldehyde and ketoses to cétotétrose configuration. This prefix will be followed
the nature of the optical rotation of the molecule (-) or (+).
CHO
C
C
CH2OH
H
H
OH
OH
CHO
C
C
CH2OH
H OH
HO H
(E)
CHO
C
C
CH2OH
HO
HO
H
H
CHO
C
C
CH2OH
H OH
HO H
(E ')
(T) (T)
(2R, 3R) (2S, 3S)
(2S, 3R) (2R, 3S)
enantiomer
diastereoisomer
enantiomer
Series D L series
mirror
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ETS License - Biochemistry 1: Carbohydrates - 7
1.5.1. Aldoses
The nomenclature is defined relative to the position of hydroxyl carried by the carbon
asymmetric neighbor of the primary alcohol function with reference to glyceraldehyde.
Filiation
The carbon chain is represented by a vertical line. The horizontal lines correspond
the OH asymmetric carbons.
o represents the aldehyde group and O the primary alcohol function.
C
CH2OH
(CHOH) n
CHO
HO H
L-glyceraldehyde
CHO
C
CH2OH
HO H
Series D L series
CHO
C
CH2OH
H OH
D-glyceraldehyde
C
CH2OH
H OH
(CHOH) n
CHO
D (-) lyxose D (+) xylose
o
O
o
O
D (-) Ribose D (-) arabinose
o
O
o
O
D (-) erythrose D (+) threose
o
O
D (+) glyceraldehyde
o
O
o
O
o
O
o
O
o
O
o
O
o
O
o
O
o
O
o
O
D (+) allose D (+) altrose D (+) glucose D (+) mannose D (+) talose D (+) galactose D (+) idose D (-) gulose
C4
C5
C6
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For aldoses, the number of stereoisomers is 2 (n-2) where n is the number of atoms of the
chain. The number of stereoisomers for each series (D or L) is 2 (n-3).
Example: aldohexoses where n is 6.
The total number of stereoisomers is equal to 24 = 16
The total number of stereoisomers for the D series is 23 = 8
Recall that stereoisomers that differ from each other only by the configuration of a single
asymmetric carbon are called epimers.
Example: D (+) glucose and D (+) mannose or D (+) glucose and D (+) galactose
Aldoses D series and L enantiomers are 2-2.
Example: D (-) ribose and L (+) Ribose
When 2 adjacent OH hydroxyl groups are arranged on the same side in the
Fisher representation, they are so-called erythro configuration, in the contrary case they are
threo said. The names of the D (+) threose and its isomer D (-) erythrose take their root
in this denomination.
1.5.2. Ketosis
The nomenclature is defined relative to the position of hydroxyl carried by the carbon
asymmetric neighbor of the furthest primary alcohol functional group of the ketone function in
reference to cétotétrose.
Filiation
The carbon chain is represented by a vertical line. The horizontal lines correspond
the OH asymmetric carbons.
o is O ketone and the primary alcohol function.
CH2OH
CO
H C OH
CH2OH
CH2OH
CO
HO C H
CH2OH
H C OH
CH2OH
(CHOH) n
C
CH2OH
O
HO C H
CH2OH
(CHOH) n
C
CH2OH
O
D-erythrulose L-erythrulose
Series D L series
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For ketoses, the number of stereoisomers is 2 (n-3) where n is the number of atoms of the
chain. The number of stereoisomers for each series (D or L) is 2 (n-4).
1.6. Physical properties of monosaccharides
1) The optical properties of their solutions are limited to change of index
refraction and optical rotation. They do not exhibit absorption in the visible or
ultraviolet.
2) Their wealth hydroxyl group gives them properties capable of polar
multiple hydrogen bonds:
- With water: they have very soluble
- With other molecules such as proteins
3) Their structure is thermodegradable (caramelization). This prevents separation
vapor phase chromatography.
1.7. Chemical properties of monosaccharides
Their chemical properties are characteristic of alcoholic hydroxyl groups and
carbonyl groups.
o
O
O
D (-) erythrulose
o
O
O
o
O
O
D (+) ribulose D (+) xylulose
D (+) allulose
o
O
O
o
O
O
D (-) fructose D (+) sorbose
o
O
O
D (-) tagatose
o
O
O
C5
C6
C4
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1.7.1. Oxidation reaction oses
1) oxidation with iodine under basic conditions
Aldose
The resulting acid is an aldonic acid. If the reaction takes place with the D-glucose is obtained
D-gluconic acid
Ketosis
The ketone group is not oxidized with iodine in a basic medium. However ketoses by
a phenomenon tautomerization (endiol) which takes place in a basic medium are balanced
with the corresponding aldose via trans-enediol. The phenomenon is a
interconversion (aldose -> ketosis)
In the trans-enediol, the C2 carbon is not asymmetric, it can undergo a rearrangement
to give a cis-enediol (epimer for OH), which may give an aldose
epimer. Converting D-glucose / D-mannose epimerization.
2) Reaction with Fehling's solution in basic medium
Aldose
Ketosis
CH2OH (CHOH) 3 C
O
CH2OH + 4 Cu (OH) 2
CH2OH (CHOH) 2 COOH
D-acid erythronic
CH2OH COOH
glycolic acid
R C
O
H
I2 + + OH- R C
OH
O
2I- + + Na + + H2O
R C
O
H
R C
OH
O
+ 2Cu (OH) 2 + Cu2O + 2H2O
brick red
C
C
OH
H OH OH H C
C
CH2OH HO H
CO
ketose enediol aldose trans-
Trans-endiol cis-D-glucose D-mannose endiol
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ETS License - Biochemistry 1: Carbohydrates - 11
3) Oxidation with nitric acid
The primary alcohol and the aldehyde is oxidized to acid functional
4) Selective oxidation in vivo to the primary alcohol
Generically, saccharides give glycuronic acids.
2.7.2. Reduction reaction oses
Aldoses and ketoses are likely to catalytic reduction on their group
carbonyl chemically by alkali metal borohydrides, or enzymatically in
giving glycitols called sugar alcohols or alditols from 4C.
2.7.3. Esterification and etherification
- Acid esterify the alcohol functions:
- The hydroxyl with alcohols give the ethers
D-glucose
NaBH4
or LiBH4
D-sorbitol
CH2OH
H OH H OH
CHO
CH2OH
O
CH2OH
H OH D-sorbitol
or LiBH4
NaBH4
D-fructose
H3PO4 OH + O P
O
O-
O-
dare phosphate ester
OH + O R
dare ether oxide
HO R + H2O
alcohol
CH2OH (CHOH) 4 CHO
HNO3
COOH
Properties "abnormal" oses
Some physical or chemical properties of the sugars are unexpected. The structure as
it has been given so far does not include the following properties.
1.8.1. Chemical Properties
1) Combination bisulfite
The aldehyde group reacts with the sodium hydrogen sulfite to give
sodium hydrogen of aldehyde which generally precipitates. This reaction occurs at pH
neutral.
Aldoses give no bisulphite combinations: their aldehyde group has
not classical chemical reactivity of a neutral pH aldehyde.
2) Reaction of acetalization
In acid, the aldehyde group reacts with two alcohol molecules to reach
forming an acetal.
D-glucose reacts only with a single methanol molecule to give a semiacétal.
The product obtained may be separated into two components of the same chemical structure but
different in optical rotation, and called:
- Α-methyl glucoside: αo = + 154 ° optical rotation at 20 ° C, concentration of 1g / ml
- Β methyl glucoside: αo = - 34 ° sodium D line (λ = 570nm), optical path 1 dm
R C
O
H
+ NaHSO3
H
R C OH
S
Na + O-
O O
H
R C OCH3
OH
R C + CH 3 OH
O
H
addition
hemiacetal
acetal
substitution
+ CH 3 OH
H
R C OCH3
OCH3
H
R C OCH3
OH
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ETS License - Biochemistry 1: Carbohydrates - 13
1.1.2. Physical Property: phenomenon mutarotation
Experience
- Crystallization of D-glucose in different solvents (ethanol, pyrimidine) results
not a single product but two products whose rotations are different. These 2
forms were described as α (+ 112 °), crystallization in ethanol, and β form
(+ 19 °), crystallization pyrimidine. These two forms are called anomers.
- Is observed for each of the shapes placed in aqueous solution, as a function of time,
evolution of optical rotation that reaches each kind the same value + 52.5 °.
This is the phenomenon of mutarotation:
This experiment suggests that D-glucose is an additional chiral center and that when
equilibrium is reached, the two forms α and β are present in solution in the reports
following respective 1/3 and 2/3.
1.9. Cyclic structure of monosaccharides
Tollens, in 1884, proposed a ring structure of glucose to interpret these properties
"abnormal" described in the previous paragraph.
1.9.1. Reacting hemi-acetalization: Cyclization
The reactivity of the carbonyl is sufficient that placed near a hydroxyl, the reaction
aldehyde / alcohol occurs. For glucose, this intramolecular acetalization can hemi-
take place with the C1-C5 carbon pairs or C1-C4 to form a heterocycle with oxygen
Six (pyranose) or 5 vertices (furanose).
[α0]
112
19
52.5
time
optical rotation at 20 ° C, concentration of 1 g / ml,
sodium D line (λ = 570nm), 1 dm optical path
α form
β form
dissolution at time t = 0
0
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ETS License - Biochemistry 1: Carbohydrates - 14
This cyclization makes the asymmetric carbon C1. The relative positions in space of 4
substituents define two stereoisomeric configurations, α and β anomers. Carbon
C1 is designated by the name anomeric carbon. Note that the forms α anomers
and β are not enantiomers but epimers.
The interconversion of α and β forms cyclical passes through the linear form.
- PH 7 relapsing forms 99% with 1/3 and 2/3 of the form α β form
- At basic pH, the predominant form is the linear form 99%
1.1.2. Representation of Haworth
The perspective representation of Haworth facilitates the representation of different forms
cyclical. The ring is perpendicular to the plane of the sheet, its forward links are
thickened. The most oxidized carbon is positioned at the right end. The position of
hydroxyl groups is based on their position in the representation of Fisher. The H
OH and to the right of representation in Fisher will find themselves below
plane of the ring.
linear form α β form
O
C
C C
CHOH
H
OH
OH
H
C
H
CH2OH
HO H O
1
3 2
4
5
6
furan furanose
hemi-acetalization
C4-C 1
O
CH2OH
H
OH
H
CHOH
C
C C
C
H
OH HO
H
C
C C
C
H
OH HO
H
O
CH2OH H
H
C
H
OH
O
H
O
D-glucose
hemi-acetalization
C1-C5
pyranose pyrane
1
3 2
4
5
6
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