Mohammad Yunus - Answers for Carbohydrates.pdf

1. BIOCHEMISTRY FOR GRADUATE STUDY I
318 701
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Orientation: Course schedule
Assoc. Prof. Dr. Yanee Trongpanich

2. 2
Diverse living organisms share common chemical features

3. Biomolecules: The molecules of life
3
• All living organisms build molecules from the same kinds of
monomeric subunits.
• The structure of a macromolecule determines its specific
biological function.

4. 4
4 types of Biomolecules
 Carbohydrates
 Lipids
 Nucleic acid
 Amino acids and Protein

5. Carbohydrates
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Learning Objective
o Define the carbohydrates, mono-, oligo- and polysaccharides
o Classify carbohydrate on the basis of their structures
o Explain glycosidic bond and the different structure of some
oligosaccharides
o Describe general characteristic of polysaccharides
o Appreciate the role of carbohydrates in biosystem
At the end of lecture students should be able to:

6. Carbohydrates
 Polyhydroxy aldehydes (-HC=O) or
ketones (-RC=O), or substances that
yield such compounds on hydrolysis.
 Some also contain nitrogen,
phosphorus, or sulfur.
 Empirical formula : (CH2O)n
starch grains (lightly stained
with iodine) in the cells of
the white potato
6

7. Carbohydrate roles
Wang's mannose-rich cluster molecule
resembles the target for an HIV-1 antibody 7
 served as fuels ; starch and glycogen
 served as structural and protective elements; cellulose, chitin
and peptidoglycan
 used as lubricate skeletal joints; glycosaminoglycan
 covalently attached to proteins or lipids act as signals and
participate in recognition and adhesion between cells;
glycoconjugates

8. Classes of carbohydrates
(Saccharide =sakcharon (Greek) = sugar)
1. Monosaccharides
2. Oligosaccharides
3. Polysaccharides
8

9. Monosaccharides
o a single polyhydroxy aldehyde or ketone unit
o Aldose : aldehyde group
Ketose : ketone group
o Empirical formula : (CH2O)n, n = 3+
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o -ose suffix; aldose , ketose
o refer to the number of carbon atom; pentose,
hexose
o refer to the funtional group ; aldohexose,
ketopentose
o common name : fructose, sorbose
aldopentose : D-ribose ketopentose : D-ribulose
Monosaccharide Nomenclature

10. • Aldose and ketose can interconvert via an enediol intermediate.
• When the structures of molecules are related in these ways
(different in the position of the hydrogen and double bonds), the
molecules are called tautomers.
Triose : aldotriose (carbonyl group) ketotriose (ketone group)
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D-glyceraldehyde Dihydroxyacetone
Enediol
intermediate

11. Properties of monosaccharides
• All monosaccharides except dihydroxyacetone contain one or more
asymmetric (chiral) carbon atoms and thus occur “stereoisomers”
• In general, a molecule with “n” chiral carbons can have 2n
stereoisomers
Aldohexose : stereoisomers = 24
Ketohexose : stereoisomers = 23
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1. D-isomer  most found in nature
2. L-isomer
Aldohexose : 24 = 16= D-isomer (8), L-isomer (8)

12. D-isomer and L-isomer are mirror images of each other
(stereoisomers) and cannot be superimposed on each other. Such
molecules with these properties are called enantiomers.
Enantiomers

13. = Two sugars differ only in the configuration around one carbon atom
D-glucose and D-mannose ( C2)
D-glucose and D-galactose ( C4)
D-erythrose and D-threose ( C2) 13
Epimer

14. (Fischer
projection)
D-Aldose
14

15. D-Ketose
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16. O
O
Common monosaccharides have cyclic structures
16
Intramolecular
hemiacetals /
hemiketals

17. Formation of two
Cyclic forms of
D-glucose
Occurs an addition
asymmetric C atom
produces 2 stereoisomers, designated
 and  -anomer
mutarotation
-D-glucopyranose
-D-glucopyranose
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D-glucose

18. C
OH
CH2OH
H
HOH2C
OH H
H
C
C
C
HO
O
C
CH2OH
OH
H
HOH2C
OH H
H
C
C
C
HO
O
4
2
3
5
1
6
1
2
3
4
5
6
- D-fructofuranose -D-fructofuranose
OH group at anomeric carbon is on the opposite side of the sugar ring from the CH2OH group : D-isomer
OH group at anomeric carbon is on the same side of the sugar ring from the CH2OH group : L-isomer
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D or L-isomer from ring structures

19. Chair form Boat form
the chair form is more
stable because it is less
sterically hindered by
neighboring substituents.
19
3-Dimentional conformation

20. Derivatives of the monosaccharides
1. Oxidation reactions :
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1.1 mild oxidation : the conversion of aldehyde group to a carboxylic acid.
“Aldonic acids”
: Food additive (acidity regulators)
Aldonic acid name: appending the suffix “-onic acid” to the root name of the
parent aldose.
Reducing sugar

21. 1.2. specific oxidation: the conversion of CH2OH group to a
carboxylic acid. “Uronic acids”
Uronic acid name: appending the suffix “-uronic acid” to the root
name of the parent aldose
Importance components of many polysaccharides 21

22. Both aldonic and uronic acids have a strong tendency to internally
esterify, called as lactone.
22
Free aldonic acids are
in equilibrium with
lactones

23. 2. Reduction reactions
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Derivatives of the monosaccharides
- made by reducing the carbonyl group of a sugar.
- The resulting polyhydroxy compounds are called alditols.
alditols name: appending the suffix “-itol”
to the root name of the parent aldose

24. 3. Deoxy sugars : an OH group is
replaced by atom H
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Derivatives of the monosaccharides
4. Phosphate sugars: made by
esterifying a phosphate group to one of
the hydroxyls.
5. Amino sugars : made by replacing
a hydroxyl of a sugar with an amine
group (NH2) or delivative NH2
(acetylated amino, NHCOCH3)

25. Oligosaccharides
 Two or more monosaccharides joined covalently by an
O-glycosidic bond.
 O-glycosidic bond : a OH group of one sugar reacts with
the anomeric carbon of the other (= formation of an
acetal from a hemiacetal and an alcohol).
 the resulting compound called a glycoside
 Glycosidic bond are readily hydrolyzed by acid but resist
cleavage by base.
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26. Formation
of Maltose
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27. 1. The sequence starts with the nonreducing end at the left using
the abbreviations of Table
The naming rules for Oligosaccharides
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Based on as follows:

28. 2. Anomeric and enantiomeric forms are designated by prefixes
(e.g., , D-)
3. The ring configuration is designated by the suffixes p (pyranose)
or f (furanose)
4. Numbers in parentheses between residue numbers are used to
identify glycosidic bonds; e.g., (1->4) means a bond from
carbon 1 of the residue on the left to carbon 4 of the residue
on the right.
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The naming rules for Oligosaccharides

29. 29
The structure of several disaccharides
Lactose: -D-galactopyranosyl-(14)-D-glucopyranose
Sucrose: -D-glucopyranosyl-(1 2)--D-fructofuranoside

30. 30
The structure of
some
oligosaccharides

31. 1. Homopolysaccharides :
single monosaccharides
2. Heteropolysaccharides:
two or more different kinds
of monosaccharides
• also called Glycans
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Polysaccharides

32. Starch
Contains 2 types of glucose polymers
1. linear polymer ( -Amylose) and 2. branch polymer (amylopectin)
 -Amylose: D-glucose residues connected by  (1 4) linkages
3D: random coil 32

33. Amylopectin
D-glucose residues connected by
 (1 4) linkages, the branch
points, occurring every 24 to 30
residues are  (1  6) linkages.
schematic of starch in an organized structure
33

34. • Like amylopectin, but more extensively branched (every 8-12
residues)
www.emc.maricopa.edu/.../BIOBK/1glycogen.gif 34
Glycogen
• Major form of storage polysaccharides in
animal cells.

35.  Dextrins are a group of low-molecular weight carbohydrates
produced by the hydrolysis of starch or glycogen.
 Dextrins are mixtures of polymers of D-glucose units linked by α-
(1→4) or α-(1→6) glycosidic bonds.
 It is used as adhesive in the manufacture of gummed tapes,
textiles and paper.
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Dextrin

36.  Dextrans are bacterial and yeast polysaccharides made
up of ( 1  6)-linked poly-D-glucose; all have ( 1  3)
branches, and some also have ( I  2) or ( I  4)
branches
 Dental plaque
Synthetic dextrans =Sephadex = Gel filtration 36
Dextran

37. Cellulose
- Is found in the cell walls of plants
- linear polymer of glucose residues linked by  (1  4)
cellobiose
- Hydrogen bond between the sheets strengthen the structure.
3D:
planar structure
37

38. Chitin
 the principal component in the exoskeletons of crustaceans,
insects, and spiders
 Is present in the cell wall of fungi and algae
 Linear homopolymer of  (1--> 4) linked N-acetyl-D-glucosamine
residues
acetylated amino group 38
Chitosan : a linear polysaccharide composed
of randomly distributed β-(1-4)-linked D-
glucosamine (deacetylated unit) and N-
acetyl-D-glucosamine (acetylated unit).

39. - A family of linear polymers composed of repeating
disaccharide units (uronic acid and hexosamine).
39
Glycosaminoglycans
- involved in a variety of extracellular functions
Hyaluronic acid (“hyalos” Greek = glass) Extracellular matrix

40. 40
The disaccharide repeating units of the common glycosaminoglycan
- Up to 50,000 repeats of the disaccharide unit
- Serve as lubricants in the synovial fluid of joints, the
vitreous humor of vertebrate eye
- extracellular matrix of cartilage and tendons, contributes
tensile strength and elasticity
- Hyaluronidase (pathogenic bacteria, sperm)

41. Heparin is a fractionated form of
heparan sulfate derived mostly from
mast cells (a type of leukocyte).
41
- contributes tensile strength of cartilage,
tendons, ligaments and the wall of aorta.
The disaccharide repeating units of the common glycosaminoglycan

42. 42

- no uronic acid and their sulfate content
is variable
-- present in cornea, cartilage, bone, and
a variety of horny structures formed of
dead cells (horn, hair, nails, ect)
- contributes the pliability of skin.
- present in blood vessels and heart
valves.
-- L-iduronate : 5-epimer of D-glucuronate
(chondroitin sulfate)
The disaccharide repeating units of the common glycosaminoglycan

43. Glycoconjugates
Role
information carriers :
transport proteins, receptors,
hormones, structural protein
• Carbohydrate is covalently joined to a protein or a lipid
such as proteoglycan, glycoprotein, glycolipid
43

44. Oligosaccharide linkages in glycoprotein
44
O-linked : anomeric carbon
linked with OH group of
Serine or Threonine
N-linked : anomeric carbon
linked with NH2 group of
Asparagine

45. 45
Proteoglycans
• glycosaminoglycan-containg
macromolecules of the cell
surface and extracellular matrix
• acts as tissue organizers
• influence various cellular
activities such as growth factor
activation and adhesion
Interactions between cells and the extracellular matrix

46. Proteoglycan
• The basic proteoglycan unit consists of a "core protein" with
covalently attached glycosaminoglycan(s).
• The point of attachment is a Ser residue, to which the
glycosaminoglycan is joined through a tetrasaccharide bridge.
46

47. Proteoglycan aggregates (Supramolecular complex)
47

48. a signal transduction
mediated by cell
membrane-type
proteoglycan
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Two major groups of
membrane heparan
sulfate proteoglycan :
1. Syndecan :
transmembrane
domain
2. Glypican : lipid
anchor (glycosyl
phosphatidylinositol
(GPI)
Transmembrane proteoglycan

49. 49
peptidoglycan
• peptide-polysaccharide complex
Bacteria classification : Gram positive : thick peptidoglycan
(Gram strain) Gram negative : thin peptidoglycan
linear copolymer of N-acetylglucosamine (GlcNAc) and
N-acetylmuramic acid (Mur2Ac) linked by (14) glycocidic bonds
and cross linked by short peptides attached to the Mur2Ac.

50. Gram positive Staphylococcus aureus
50

51. Gram negative
E.coli
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52. Glycolipid
• Oligosaccharide head group of
glycolipid of Blood group
• Gangliosides 52

53. Questions
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