Chapter 13 Problems

1
Chapter 13 Problems

• 1-21, 22, 25, 36, 38, 50
• Text Errors
• 441 fig 13.10 missing O
• 450 fig 13.15 C O atoms labeled

2
Emil Fischer

• There exists no better thing in the world than
  beer to blur class and social differences and to
  make men equal.

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Chapter 13 Carbohydrates

• OUTLINE
• Monosaccharides Glucose, Galactose, Fructose,
  Ribose, Glyceraldehyde
• Nomenclature Structure
• Stereochemistry Epimers
• Glycosidic Linkages acetals
• Disaccharides
• Polysaccharides
• Modified sugars Functional Groups
• Aldonic Uronic Acids
• Sulfates N-acetyl derivatives

4
Monosaccharides
HC O
CH2OH
OH
H
O
C
C
CH2OH
CH2OH

• Monosaccharides single carbonyl derivatives of
  polyhydroxy alcohols
• Ketoses - Carbonyl ketone (dihydroxyacetone)
• Aldoses - Carbonyl aldehyde (D-glyceraldehyde)

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Monosaccharides

• Contain only C, H, and O Cx(H2O)x
• Most abundant biomolecules
• Classified by location of their carbonyl group
  (ketose or aldose) and the number of C atoms (3
  and above) aldotriose, ketotetrose, -pentose,
  -hexose, -heptose, etc.)

6
Structures

• Fisher versus Haworth Projections
• D-Glucose

D-Glucose
?-D-Glucopyranose
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Structures

• Fisher convention Horizontal lines project
  toward the readers vertical lines project away.

CHO
CHO
HO
OH
H
H
CH2OH
CH2OH
L-Glyceraldehyde
D-Glyceraldehyde
8
Structures

• Fisher convention Horizontal lines project
  toward the readers vertical lines project away.

CHO
CHO
H
HO
OH
H
CH2OH
CH2OH
L-Glyceraldehyde
D-Glyceraldehyde
9
Structures

• Fisher versus Haworth Projections
• D-Glucose

D-Glucose
?-D-Glucopyranose
10
Structure

• Haworth Projections
• D-Glucose

pyran
?-D-Glucopyranose
furan
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Carbohydrates

• Haworth Projections Hemiacetal or Hemiketal
  Conformation

Hemiacetal
Alcohol Aldehyde
CH2OH
5
H
O
OH
H
1
H
OH
HO
H
5
OH
H
?-D-Glucopyranose (pyranose form)
D-Glucose
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Carbohydrates

• Fisher versus Haworth Projections
• D-Glucose

D-Glucose
?-D-Glucopyranose
13
Carbohydrates

• Formation of cyclic form
• D-Glucose

C5-hydroxyl attacks carbonyl
HOCH2
OH
H
H
C
O
H
H
OH
HO
OH
H
D-Glucose (alcohol aldehyde)
?-D-Glucopyranose (a hemiacetal)
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• Haworth Projections
• ? anomer 1 OH and 5 CH2OH opposite
• ? anomer 1 OH and 5 CH2OH same

36.4
63.6
CH2OH
CH2OH
H
H
O
O
H
OH
H
H
1
1
H
H
OH
OH
HO
HO
OH
H
OH
H
OH
H
?-D-Glucopyranose (pyranose form)
?-D-Glucopyranose (pyranose form)
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• CHAIRS
• ? anomer 1 OH and 5 CH2OH opposite
• ? anomer 1 OH and 5 CH2OH same

36.4
63.6
OH
CH2OH
CH2OH
CH2OH
CH2OH
o
o
o
OH
o
OH
OH
OH
HO
HO
HO
HO
HO
OH
OH
OH
OH
OH
OH
?-D-Glucopyranose (pyranose form)
?-D-Glucopyranose (pyranose form)
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Carbohydrates

• EPIMER SERIES
• Vary by configuration about one chiral carbon
• Each Aldoses have 2n-2 epimers Ketoses have 2n-3
  epimers based on the of non-carbonyl chiral
  carbons
• D- versus L- determined by penultimate carbon
  (counting from carbonyl group)
• Aldotriose (D-glyceraldehyde) Aldohexoses
  (D-glucose)
• Ketotrioses (dihydroxyacetone) Ketohexoses
  (D-fructose)

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Sugar Derivatives

• Aldonic Acids mild oxidation of aldehyde to a
  carboxylic acid (Gluconic Acid a lactone)
• Uronic Acids oxidation of primary alcohol to
  carboxylic acid (Glucuronic Acid)

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REDUCING SUGARS(Aldoses)
Tollens Test
Ag(NH3)2
OH-
Lactone (cyclic ester) Gluconic Acid Oxidized
Form of Glucose
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Carbohydrates

• Monomer to Polymers Glycans
• D-Glucose to ?-Amylose to Glycogen
  (Homopolysaccharides)

CH2OH
CH2OH
CH2OH
H
H
H
O
H
O
O
H
H
H
H
H
H
OH
H
H
OH
OH
O
HO
OH
OH
H
OH
H
OH
H
?-Amylose to Amylopectin or Glycogen (? (1?4)
glycosidic bond)
?-D-Glucose
(Text error p. 444)
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Storage Carbohydrates

• Glucose Polymers

Amylose -- repeating ? (1?4) glycosidic bond.
Broken down during digestion by amylase and a
debranching enzyme. (Helix 6 units/turn I2
test). Amylopectin (plant starch)-- repeating ?
(1?4) glycosidic bond repeating ? (1?6)
glycosidic bond every 24-30 residues up to
1,000,000 residues! Glycogen (animal sugar
storage)-- repeating ? (1?4) glycosidic bond
repeating ? (1?6) glycosidic bond every 8-12
residues. Mobilized from muscle with glycogen
phosphorylase from non-reducing end.
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Storage Carbohydrates

• Glucose Polymers

• Cellulose -- repeating ? (1?4) glycosidic bond
  for up to 15,000 residues. Structural function
  in plant cell walls antiparallel chains of 40
  monomers in 3-D H-bonded lattice.
• Difficult to digest due to linkage and tightly
  H-bonded structure. Cellulases requiredfound
  only termites herbivore microorganisms

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Structural Carbohydrates

• Cellulose

CH2OH
CH2OH
CH2OH
H
H
H
O
O
O
OH
H
H
H
O
H
OH
H
H
OH
OH
HO
H
H
H
OH
H
OH
H
OH
H
? (1?4) glycosidic bond
?-D-Glucose
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Sugar Derivatives

• Glycerol, Ribitol, Inositol - reduction of
  carbonyl to form acyclic and cylic polyhydroxy
  alcohols (sorbose ? sorbitol, xylose ? xylitol)
• glyceraldehye ?
  glycerol

CHO
CH2OH
OH
H
OH
H
CH2OH
CH2OH
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Sugar Derivatives

• Deoxy and Dideoxy Sugars (DNA) reduced sugars
  2 endo vs. 3 endo
• Amino/Acetyl Sugars 2 OH replaced by NH3
  glucosamine and galactosamine
• (2-amino-2-deoxy)
• GLYCOSIDES joins monomers by anomeric carbon of
  first monomer to any OH on next monomer

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Carbohydrate Nomeclature

• Monosaccharide to Disaccharide
• Lactose

Reducing End Rx with mild Oxid. Agents
CH2OH
CH2OH
HO
OH
H
O
O
H
H
O
H
OH
H
OH
H
H
H
OH
H
OH
H
Galactose Glucose (? (1?4) glycosidic linkage)
O- ?-D-Galactopyranosyl- (1?4) D-glucopyranose
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Carbohydrates

• Monosaccharide to Disaccharide
• Sucrose
• Most abundant disaccharideplant sugar transport

CH2OH
H
HOCH2
H
O
O
H
H
1
2
H
HO
H
OH
O
HO
CH2OH
OH
H
OH
H
Glucose Fructose (? (1?2) glycosidic linkage)
O-?-D-glucopyranosyl-(1?2)?-D-fructofuranoside
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Structural Carbohydrates

• Chitin
• Insect Skeletons

CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
H
H
H
H
O
H
O
O
O
O
OH
H
H
H
H
H
O
H
H
OH
OH
H
H
OH
OH
H
OH
HO
HO
H
H
H
H
H
NHCOCH3
H
NHCOCH3
H
H
H
H
H
NHCOCH3
NHCOCH3
NHCOCH3
? (1?4) glycosidic bond
N-Acetylglucosamine
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Structural Carbohydrates

• Glycosaminoglycans

• Combinations of uronic acids/sulfates and
  hexosamines
• Extracellular
• Viscoelastic and lubricating Cartilage, tendon,
  skin, vessels
• Examples Hyaluronate, Chondroitin-4-sulfate,
  Heparin, Keratan sulfate

COO-
CH2OH
H
H
O
O
H
H
H
OH
H
H
HO
H
O
OH
H
H
NHCOCH3
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Glycoproteins

• Proteoglycans bottlebrush structure
  consisting of core protein with bristles of
  glycosaminoglycans.
• N-linked oligosaccharides via Asn
• O-linked via Ser, Thr
• Highly negatively charged and hydrated for
  cushioning effect

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Peptidoglycan

• N-acetylglucosamine N-acetylmuramic acid with
  tetrapeptide crosslinked by pentaglycine bridges
• Bacterial cell walls
• Thick layer in Gram bacteria (Staph, Strep)
• Thin layer in Gram bacteria (E. coli)
• Natural occurrence of D-amino acid
• Site of penicillin activities. Penicillin mimics
  the crosslink structure and inhibits cells wall
  synthesis hence, selective for bacteria

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Glycoproteins

• Glycosylated Proteins
• Often secreted and membrane-associated proteins
• Anomeric carbon is N-linked to protein via Asn
  O-linked via Ser, Thr
• Negatively charged and hydrated for cushioning
  effect (chondroitin glucuronate-N-acetylgalactosa
  mine-4-sulfate)
• Often rigidly positioned at membrane surface
  loops of proteins
• OFTEN HIGHLY IMMUNOGENIC A/B/O blood groups
• Fucose GluNAc Gal

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Glycoproteins

• Glycosylated Proteins
• Responsible for receptor-mediated cellular
  binding/communication/recognition events
• Antibody recognition and binding sites
• Egg recognition and binding by sperm
• Parasite, Bacteria and Virus attachment sites
  during infections (HIV gp41 gp120)
• Cellular contact inhibition (cancer)
• Protein tagging for transport/receptor
  recognition