Transcript Camp 1 - UCSC Directory of individual web sites

20 Chair Conformations
• For pyranoses, the six-membered ring is more
accurately represented as a chair conformation.
HO
HO
CH2 OH
O
anomeric
carbon
OH()
OH
 -D -Glu copyran os e
( - D -Glucos e)
HO
HO
CH2 OH
OH
O
C
OH H
D -Glucos e
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HO
HO
CH2 OH
O
HO
OH( )
- D -Glu copyran os e
(  - D -Glucose)
20-1
20 Chair Conformations
• In both Haworth projections and chair conformations,
the orientations of groups on carbons 1- 5 of -Dglucopyranose are up, down, up, down, and up.
6
CH2 OH
5
O OH()
H
H
4 OH
1
H
HO
H
3
2
H OH
-D -Glucop yranose
(Haw orth p rojection)
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6
CH2 OH
4
HO
HO
O
5
3
2
OH 1
OH( )
- D -Glucopyranose
(ch air con formation)
20-2
20 Mutarotation
• Mutarotation: the change in specific rotation that
accompanies the equilibration of - and anomers in aqueous solution.
• Example: when either -D-glucose or -D-glucose is
dissolved in water, the specific rotation of the solution
gradually changes to an equilibrium value of +52.7°,
which corresponds to 64% beta and 36% alpha forms.
HO
HO
CH2 OH
O
OH
OH
-D -Glucopyranose
[] D 2 5 = + 18.7°
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HO
HO
CH2 OH
OH
O
C
HO
H
Open-chain form
HO
HO
CH2 OH
O
HO
OH
-D -Glucopyranose
[] D 2 5 = +112°
20-3
20 Physical Properties
• Monosaccharides are colorless crystalline solids,
very soluble in water, but only slightly soluble in
ethanol
• Sweetness relative to sucrose:
S w eetness
Relative to
Carbohydrate
S ucrose
fructos e
1.74
sucrose (tab le sugar) 1.00
honey
0.97
glu cose
0.74
maltose
0.33
galactos e
0.32
lactose (milk su gar) 0.16
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S w eetness
Relative to
Artificial
Sw eetener
S ucrose
saccharin
450
acesu lfame-K
200
aspartame
180
20-4
20 Formation of Glycosides
anomeric
• Treatment
CHof
OHa monosaccharide, all of which exist
carbon
2
O OH
almost exclusively
in cyclic
hemiacetal forms,
H
+
H
H
+
CH
OH
3
OH H
with an alcohol
gives an
-H2 Oacetal.
HO
yes
H
no
anomeric
anomeric
glycos idic
H OH
carbon
CH2 OH
CH2CH
OH2 OHcarbon
CH2 OH
bond
-DO-Glu
copyran
os
e
OH
O
OH
O OCH3
+H
H H H OH(-D -Glu cose) +
H
H H
H
H
H
+
CH
OH
+
CH
OH
+
3
3
OH OH
OH H
H H
OH H
-H
O
-H
O
2
2
HO HO
H
HO
OCH3
H H
HO
glycos
idic
H H
H OH
glycos idic
OH OH
H OH
CH2 OH
CH2 OHCH OH
CH
OH copyran os ide
bond
2-glu
bond
-D-D
-Glu-Glu
copyran
os
e
2
Methyl
-D
-glu
copyran
os
ide
Methyl
-D
copyran os e
OH
O OCH3
H
OH
H
O
OCH
(-D -Glu cose)
(Methyl
-D
-glu
coside)
(Methyl
-D
-glucos ide)
3
H
H
H H
(-D -Glu cose)
H
+
OH H
OH H H
+
H
HO
OH H
H
OCHOH
HO
3
H
HO
OCH3
HO
Hemiacetal
Acetals
α
+
β
H
OH
H OH
H OH
os ide Mutarotation
Methyl -D -glu copyran
ide
mutarotation Methyl
=Yes -D -glu copyran
= HNoosOH
Methyl
copyran os(Methyl
ide Methyl
-Dide)
-glu copyran os ide
(Methyl
-D-D
-glu-glu
coside)
-D -glucos
(Methyl -D -glu coside)
(Methyl -D -glucos ide)
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20-5
20
Formation of Glycosides
• A cyclic acetal derived from a monosaccharide is called a glycoside.
•The bond from the anomeric carbon to the -OR group is called a glycosidic bond.
•Mutarotation is not possible in a glycoside because an acetal, unlike a hemiacetal,
•is not in equilibrium with the open-chain carbonyl-containing compound.
Glycosides are stable in water and aqueous base,
but like other acetals, are hydrolyzed in aqueous acid to an alcohol
and a monosaccharide.
•Glycosides are named by listing
the alkyl or aryl group
anomeric
CH2 OH
carbon
bonded to oxygen
followed
by the
name
O
OH
H
+
H
H
+ CH3 OH
OH
anomeric
H ending
of the carbohydrate
in which
the
-e
-H2 Ois replaced by -ide.
HO
H
CH OH
2
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carbon
glycos idic
H OH
O anomeric
CH2 OH
CH2 OH
bond
carbon
HCH2 OH OH
+
-D -Glu copyran os e
OH
O OH
H
H
O
OCH
3
H
H
+
H
(-D -Glu cose)
+ CH3 OH
HOH H
H
H
H
+ CH3 OH
-H2 O
+
OH H
OH H
OH H
-H2 O
HO
HO
H
HO
H H
OCH3
HO
glycos
idic
glycos
idic
HH OHOH
H OH
CH2 OH H OH
CH2 OH CHbond
CH2 OH
OH
bond
-D -Glu copyran os e
2
Methyl
-D
-glu
copyran
os
ide
Methyl
-D
-glu copyran os ide
-D -Glu copyran os e
OH
O OCH3
H
H
(-D -Glu cose)
O
O
OCH
(Methyl
-D -glu coside)
H (Methyl -D -glucos ide)
H
3
H
H
H
(-D -Glu cose)
+
OH H
OH H H
H
H
HO
HO
+ OCH3
OH
20-6
OH
H
20 Reduction to Alditols
• The carbonyl group of a monosaccharide can be
reduced to an hydroxyl group by a variety of
reducing agents, including NaBH4 and H2 in the
presence of a transition metal catalyst.
• The reduction product is called an alditol.
HO
HO
CH2 OH
O
OH
OH
-D -Glucop yranose
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CHO
H OH
HO H
NaBH4
H OH
H OH
CH2 OH
D -Glu cose
CH2 OH
H OH
HO H
H OH
H OH
CH2 OH
D -Glucitol
(D -Sorbitol)
alditol
20-7
20 Reduction to Alditols
• Sorbitol is found in the plant world in many berries and
in cherries, plums, pears, apples, seaweed, and algae.
• It is about 60 percent as sweet as sucrose (table sugar)
and is used in the manufacture of gums, candies and
as a sugar substitute for diabetics.
•These four alditols are also common in the biological world.
CH2 OH
HO
OCH2 OH
HO
H
OHOH
HOH OH
CH2 OH
-D -Glucop yranose
Erythritol
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CHO
CH2 OH
HO
HH
OH CH2 OH
HO HO
H
OH
H H
NaBH4
H
OH
HO
H
H OH
H
OH
OH
H OH H
CH2 OH
CH2 OH CH2 OH
D -Mannitol
D -Glu coseXylitol
CH2 OH
H OH
HO H
H OH
H OH
CH2 OH
D -Glucitol
(D -Sorbitol)
20-8
20 Oxidation to Aldonic Acids
• The aldehyde group of an aldose is oxidized under basic
conditions to a carboxylate anion.
• The oxidation product is called an aldonic acid.
• A carbohydrate that reacts with an oxidizing agent to form an
aldonic acid is classified as a reducing sugar (it reduces the
oxidizing agent).
O
H
C
HO
HO
CH2 OH
O
OH
OH
- D-Glu copyran ose
( - D-Glu cose )
O-
O
C
H
HO
H
H
OH oxidi zi n g
H
OH
agen t
H
HO H
OH
basi c
H
OH
OH s ol u tion
H
OH
CH2 OH
CH2 OH
D-Glu cose
D-Gl u con ate
enediol intermed.
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20-9
20 Oxidation to Uronic Acids
• Enzyme-catalyzed oxidation of the primary
alcohol at C-6 of a hexose yields a uronic acid.
e.g. Enzyme-catalyzed oxidation of D-glucose,
yields D-glucuronic acid.
CHO
e n z ym eH
OH
catalyz e d
HO
H
oxidati on
H
OH
H
OH
CH2 OH
D-Glu cose
CHO
H
OH
COOH
O
HO
H
HO
H
OH
HO
OH
H
OH
COOH
D-Glu cu ron i c aci d
Fisher proj. (a u ron i c aci d)
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OH
Chair conformation
20-10
20 D-Glucuronic Acid
• D-Glucuronic acid is widely distributed in the plant and
animal world.
•In humans, it is an important component of the acidic
polysaccharides of connective tissues, e.g. collagen.
Used by the body to detoxify foreign phenols and alcohols;
in the liver, compounds  converted to glycosides of
glucuronic acid and excreted in the urine.
-
HO
HO
Propofol
Propofol
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COO
HO COO O O
O
HO HO
HO
OH O
OH
A u rin e-s olu ble glucuronide
A u rin e-s olu ble glucuronide
20-11
20 Two Volunteers needed. . .
1 male
1 female
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20-12
20 Testing for Glucose
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20-13
20 Phosphate Esters
• Mono- and diphosphoric esters are intermediates
in the metabolism of monosaccharides.
•For example, the first step in glycolysis is conversion of
•D-glucose to a-D-glucose 6-phosphate.
•Note that at the pH of cellular and intercellular fluids, both acidic
protons of a diphosphoric ester are ionized, giving it a charge of -2.
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20-14
20 Disaccharides
e.g. Sucrose (table sugar)
Sucrose is the most abundant disaccharide in the biological
world; it is obtained principally from the juice of sugar cane and
sugar beets.
•Sucrose is a nonreducing sugar.
CH2 OH
O
OH
1
HO
HO
OH
HO
OH
O
O
HO 2
CH2 OH
1
OH
HOCH2
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a u n i t of-Dglu copyran ose
CH2 OH
O
HOCH2
O
HO
1
O
2
-1,2-glycosi dic bon
a u n i t of-Dfru ctofu ran os e
CH2 OH
OH
1
20-15
20 Disaccharides
• Lactose
Lactose sugar present in milk; 5-8% human milk,
4-6% cow's milk.
•Little sweetness: added to cheap foods ~ fillers . . .
•D-galactopyranose bonded by a b-1,4-glycosidic bond
to carbon 4 of D-glucopyranose.
•Lactose is a reducing sugar. Why?
CH2 OH
O
OH
CH2 OH
O
OH
4
OH
OH
CH2 OH
-1,4-glycosid ic bond
O
4
O
1
OH
In equilb. w/ Open chain form~
can be oxidized to carboxylate
OH
HO
1
OH
CH2 OH
O
HO
O
OH
OH
O
OH
HO
HO
CH2 OH
O
OH
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H
C
OH
- D-Glu copyran ose
( - D-Glu cose )
O-
O
C
H
HO
H
H
OH oxidi zi n g
H
OH
agen t
H
HO H
OH
basi c
H
OH
OH s ol u tion
H
OH
CH2 OH
CH2 OH
D-Glu cose
D-Gl u con ate
20-16
20 A, B, AB and O Blood types
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20-17
20
Antigen
Anti-bodies
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20-18
20 Disaccharides
• Maltose
• Present in malt, the juice from sprouted barley and
other cereal grains.
• Maltose consists of two units of D-glucopyranose
joined by an -1,4-glycosidic bond.
• Maltose is a reducing sugar.
1
HOCH2 O
HO
CH2 OH
4
O
OH
OH
HO
OH
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O
OH
HO
HO
-1,4-glycosi dic
bon d
CH2 OH
O
1
OH 4 CH2 OH
O
O
OH
HO
OH
20-19
20 Polysaccharides
• Polysaccharide: a carbohydrate of many
monosaccharides joined by glycosidic bonds.
• Starch: a polymer of D-glucose, E stores in plants
• Two forms: amylose and amylopectin.
• 25% Amylose, unbranched chains w/ 4000 D-glucose units joined
by -1,4-glycosidic bonds.
• 75% Amylopectin, has branched chains with up to 10,000
D-glucoses, joined by -1,4-glycosidic bonds;
at branch points, new chains of 24 to 30 units are started by -1,6glycosidic bonds.
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20-20
20 Polysaccharides
• Figure 20.3 Amylopectin.
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20-21
20 Polysaccharides
• Glycogen is the energy-reserve carbohydrate for
animals.
• Glycogen is a branched polysaccharide of
approximately 106 glucose units joined by -1,4- and 1,6-glycosidic bonds.
• The total amount of glycogen in the body of a wellnourished adult human is about 350 g, divided almost
equally between liver and muscle.
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20-22
20 Polysaccharides
•
Cellulose linear polysaccharide - D-glucose units, -1,4-glycosidic
bonds.
• ~ molecular weight of 400,000 g/mol, corresponding to
approximately 2200 glucose units per molecule.
• Cellulose align themselves side by side into fibers . . OH groups
form numerous intermolecular H-bonds.
• This arrangement of parallel chains in bundles gives cellulose
fibers their high mechanical strength.
• reason why cellulose is insoluble in water.
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20-23
20 Polysaccharides
Cellulose (cont’d)
• Humans can’t use cellulose, lack digestive enzymes -glucosidases,
catalyze hydrolysis of -glucosidic bonds.
• Humans have only -glucosidases; hence, the polysaccharides we use as
sources of glucose are starch and glycogen.
• Many bacteria and microorganisms have -glucosidases and can digest
cellulose.
• Termites have such bacteria in their intestines and can use wood as their
principal food.
• Ruminants (cud-chewing animals) and horses can also digest grasses
and hay.
20-24
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20 Acidic Polysaccharides
• Acidic polysaccharides: a group of polysaccharides
that contain carboxyl groups and/or sulfuric ester groups, and play
important roles in the structure and function of connective tissues.
• There is no single general type of connective tissue.
• Large number of highly specialized forms, such as
cartilage, bone, synovial fluid, skin, tendons, blood
vessels, intervertebral disks, and cornea.
• Most connective tissues are made up of collagen, a
structural protein, in combination with a variety of
acidic polysaccharides.
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20-25
20 Acidic Polysaccharides
• e.g. Hyaluronic acid
• contains from 300 to 100,000 repeating units.
• is most abundant in embryonic tissues, connective
tissues (synovial fluid) the lubricant of joints
-the vitreous of the eye: provides a clear, elastic gel
that maintains the retina in its proper position
D -glucu ronic acid
N-Acetyl-D -glu cosamine
-
4
HO
COO
3
4
O HO
O
1
OH
CH2 OH
O
1
3
O
NH
C
H3 C
O
The rep eating unit of h yalu ronic acid
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20-26
20 Acidic Polysaccharides
• Heparin: a heterogeneous mixture of variably
sulfonated polysaccharide chains, ranging in
molecular weight from 6,000 to 30,000 g/mol.
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20-27
20 Acidic Polysaccharides
• Heparin (cont’d)
• Heparin is synthesized and stored in mast cells of
various tissues, particularly the liver, lungs, and gut.
• The best known and understood of its biological
functions is its anticoagulant activity (blood thinner).
• It binds strongly to antithrombin III, a plasma protein
involved in terminating the clotting process.
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20-28