reactions of carbohydrates hemiacetal formation reduction oxidation osazone formation chain...
TRANSCRIPT
Reactions of carbohydrates
Hemiacetal Formation
Reduction
Oxidation
Osazone Formation
Chain Shortening
Chain Lengthening
Cyclic hemiacetals• Form readily when
– hydroxyl and carbonyl groups are in the same molecule
– and a five or six-membered ring can form
aldehyde alcoholhemiacetal
HOCHO
O
OH
Haworth ProjectionsMost commonly drawn with the anomeric carbon on the right
and the hemiacetal oxygen to the back right• anomeric carbonanomeric carbon: the new stereocenter resulting from cyclic
hemiacetal formation• anomersanomers: carbohydrates that differ in configuration at their
anomeric carbonsThe designation - means that -OH on the anomeric
carbon is cis to the terminal -CH2OH; - means that it is trans
O
CH2OHOH
O
CH2OH
OH-anomer -anomer
Anomericcarbon
As a solid, glucose exists as a ring structure.
In a solution, 99% of the glucose is in the ring structure. The other 1% is the open chain.
OO
CC || ||
||
||
HH||CC||CC||CC||CC||CC||HH
|| OHOH
|| HH
|| OHOH
|| OHOH
|| OHOH
HH
||HOHO
||HH
||HH
||HH
D-glucose
1.
2.
3.
4.
5.
6.
-D-glucose
-D-glucose
1.
OH
OH
OH
OH
OHO
2.3.4.
5.
6.
OH
1.
OH
OH
OH
OH
O
2.3.4.
5.
6.
Ring Formation72%
Conformational Formulas• compare the orientations of groups on carbons
1-5 in the Haworth and chair representations of -D-glucopyranose
• in each case they are up-down-up-down-up
-D-Glucopyranose(chair conformation)
OCH2 OH
HOHO
OHOH ()
-D-Glucopyranose(Haworth projection)
H
H OH
HHO
HOH ()
OH
H
CH2 OHO
OHOH
CC ||||
||||
HH||CC||CC||CC||CC||CC||HH
|| OO
|| HH
|| OHOH
|| OHOH
|| OHOH
||HOHO
||HH
||HH
||HH
D-fructose
HO
OH
OHHO
OHO
-D-fructose
-D-fructose
||
HO
OH
OHHO
OHO
Haworth of D-Fructose
Mutarotation• Mutarotation: the change in specific rotation that
occurs when an or form of a carbohydrate is converted to an equilibrium mixture of the two
+80.2
+80.2
+52.8
+150.7-D-galactose
-D-galactose
[] after Mutarotation
(degrees)[]
Monosaccharide% Present at Equilibrium
28
72
64
36-D-glucose
-D-glucose+112.0
+18.7
+52.7
+52.7
(degrees)
OH
OOH
CH2OHHO
HO
O
OHOH
CH2OHHO
HO
O
OH
CH2OHHO
HO
OH
D-galactose
-D-galactopyranose -D-galactopyranose
[]D25 = + 150.7o[]D
25 = + 52.8o72%
Mutarotation
EpimerizationIn base, H on C2 may be removed to form
enolate ion. Reprotonation may change the stereochemistry of C2.
Enediol RearrangementIn base, the position of the C=O can shift.
Chemists use acidic or neutral solutionsof sugars to preserve their identity.
Reduction of Simple Sugars• C=O of aldoses or ketoses can be reduced
to C-OH by NaBH4 or H2/Ni.
• Name the sugar alcohol by adding -itol to the root name of the sugar.
• Reduction of D-glucose produces D-glucitol, commonly called D-sorbitol.
• Reduction of D-fructose produces a mixture of D-glucitol and D-mannitol.
Oxidation by Bromine
Bromine water oxidizes aldehyde, but not ketone or alcohol; forms aldonic acid.
Aldose Oxidation to Aldonic Acids• Oxidation of the -CHO group of an aldose to a
-CO2H group can be carried out using Tollens’, Benedict’s, or Fehling’s solutions
Precipitates asa silver mirror
+
O
O
RCH
Ag(NH3)2+ RCO
- NH4
+Ag
Tollens' solution
NH3, H2O+
citrate ortartrate buffer
Precipitates as a red solid
++O
Cu2+ RCO- Cu2 O
O
RCH
Ketose Oxidation to Aldonic Acids• 2-Ketoses are also oxidized by these reagents
because, under the conditions of the oxidation, 2-ketoses equilibrate with isomeric aldoses
An aldoseAn enediolA 2-ketose
CH2OH
C=O
CH2OH
C-OH
CH2OH
CHOH
CHOH
CH2OH
CHO
(CHOH)n (CHOH)n (CHOH)n
Oxidation by Tollens Reagent• Tollens reagent reacts with aldehyde, but
the base promotes enediol rearrangements, so ketoses react too.
• Sugars that give a silver mirror with Tollens are called reducing sugars.
• All monosaccharides are reducing sugars
Nonreducing Sugars• Glycosides are acetals, which stable in base, so they do
not react with Tollens reagent.• Some disaccharides are also acetals (nonreducing).• All polysaccharides are also acetals, (nonreducing).
Oxidation by Nitric AcidNitric acid oxidizes both the aldehyde and the
terminal alcohol; forms aldaric acid.
Formation of Glycosides• React the sugar with alcohol in acid.• Since the open chain sugar is in equilibrium with
its - and -hemiacetal, both anomers of the acetal are formed.
• Aglycone is the term used for the group bonded to the anomeric carbon.
Ether Formation• Convert all -OH groups to -OR, using a
modified Williamson synthesis, after converting sugar to acetal, stable in base.
Ester FormationAcetic anhydride with pyridine catalyst converts
all the oxygens to acetate esters.
Osazone FormationBoth C1 and C2 react with phenylhydrazine.
Osazone
Sugars that differ in configuration only at the -carbon Give the same product.
Ruff DegradationAldose chain is shortened by oxidizing the
aldehyde to -COOH, then decarboxylation.
Kiliani-Fischer Synthesis• This process lengthens the aldose chain.
• A mixture of C2 epimers is formed.
Determination of Ring Size
• Haworth determined the pyranose structure of glucose in 1926.
• The anomeric carbon can be found by methylation of the -OH’s, then hydrolysis.
O
H
OH
H
HO
HO
H
OH
H
C
H
H2OHexcess CH3I
Ag2O O
H
OCH3
H
CH3O
CH3O
H
O
HH
C
CH3
H2OCH3H3O
+
O
H
OH
H
CH3O
CH3O
H
O
HH
C
CH3
H2OCH3
Periodic Acid Reactions• Periodic acid ( HIO4 or H5IO6 ) cleaves the C-C bond
between an alcohol and an adjacent alcohol (vicinal) or carbonyl group.
• Does not affect ethers or acetals.• Two carbonyl compounds are formed:
1° alcohols oxidize to formaldehyde 2° alcohols oxidize to aldehydes
aldehydes oxidize to formic acid
ketones oxidize to carboxylic acids
carboxylic acids oxidize to CO2
Use of Periodic Acid Cleavage
• Separation and identification of the products determine the size of the ring.
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/M
Ni+
D-Glucitol(D-Sorbitol)
D-Glucose
H2
CHO
CH2OH
OHHHHOOHHOHH
CH2OH
CH2OH
OHHHHOOHHOHH
You try it:Oxidation of which two hexoses would give the
same product??
H
CHO
OH
HHO
OHH
OHH
CH2OH
H
CHO
OH
OHH
HHO
OHH
CH2OH
d-(+)- glucose L- (+)- gulose
+
H
X
OH
HHO
OHH
OHH
XCore of alcohols - mild oxidation or strong oxidation
No Symmetry
Same product
diastereomers
Question #1Which of the following aldaric
acids are optically active?C and D
A B C D ENo stereocenter meso R, R S, S meso
H
CHO
OH
HHO
OHH
OHH
CH2OH
CHO
CH2OH
d-(+)- glucose
+
H
X
OH
HHO
OHH
OHH
X
Same product
Question #2Draw a hexose that would give the same
aldaric acid product as D-Glucose
D
H
CHO
OH
HHO
OHH
OHH
CH2OH
H
CHO
OH
OHH
HHO
OHH
CH2OH
d-(+)- glucose L- (+)- gulose
+
H
X
OH
HHO
OHH
OHH
XCore of alcohols - mild oxidation or strong oxidation
No Symmetry
Same product
diastereomers
Question #2Draw a hexose that would give the same
aldaric acid product as D-Glucose
D
(2R, 3R, 4R) (2S, 3R, 4R) (2R, 3S, 4R) (2S, 3S, 4R)
H OOHHOHHOHH
CH2OH
D-Ribose
Question #3There are four D-aldopentoses. Draw Fischer
projections of each of them. Then draw Fischer projections of the aldaric acids they would yield. Label each center as a R or S configuration. Circle the aldaric acids that are optically inactive?
H OHHOOHHOHH
CH2OH
D-Arabinose
H OOHHHHOOHH
CH2OH
D-Xylose
H OHHOHHOOHH
CH2OH
D-Lyxose
Question #3There are four D-aldopentoses. Draw Fischer
projections of each of them. Then draw Fischer projections of the aldaric acids they would yield. Label each center as a R or S configuration. Circle the aldaric acids that are optically inactive?
HO OOHHOHHOHH
D-Ribose
HO OHHOOHHOHH
D-Arabinose
HO OOHHHHOOHH
D-Xylose
HO OHHOHHOOHH
D-Lyxose
MESO (S,S) MESO (S,S)
O O O OHOHOHOHO
Question #4
Select the compounds that would produce the same osazone.
A and D, B and C
Common Modifications to monosaccharides
Deoxy sugars
Amino sugars
Glycosides (acetal)
Deoxy Sugar
Amino Sugar
Glucosamine
HO O
H
H
HO
H
HNH2
H OH
OH
Formation of Glycosides - Acetals
• A monosaccharide hemiacetal can react with a second molecule of an alcohol to form an acetal
O
OH
O
OCH3
CH3OH
H+
A ‘glycoside’ bond
Glycosides• Glycoside bond: the bond from the anomeric carbon of the
glycoside to an -OR group.
• Cyclic acetals are not in equilibrium with their open chain carbonyl-containing forms. Glycosides do NOT undergo mutarotation.
• List the name of the alkyl or aryl group attached to oxygen followed by the name of the carbohydrate with the ending -e replaced by -ide– methyl -D-glucopyranoside– methyl -D-ribofuranoside
Formation of GlycosidesA methyl -D-glucoside
Methyl -D-glucopyranoside
O
CH2 OH
H
OH
OCH3()H
HOH
OHH
H
OCH2 OH
HOHO
OHOCH3()
Haworth projectionChair conformation
Is this a reducing sugar glycoside? NO!
Disaccharides
Maltose
Lactose
Sucrose
Cellobiose
Disaccharides
• Three naturally occurring glycosidic linkages:
• 1-4’ link: The anomeric carbon is bonded to oxygen on C4 of second sugar.
• 1-6’ link: The anomeric carbon is bonded to oxygen on C6 of second sugar.
• 1-1’ link: The anomeric carbons of the two sugars are bonded through an oxygen.
Yes!
Maltose• From malt, the juice of sprouted barley and
other cereal grains. (Cellulose)
OHOHO
OH
CH2OH
CH2OH
OHHO
OOH
O
-maltose becausethis -OH is beta
-1,4-glycoside bond
•Is this a reducing sugar?
NO
Yes!
4-O-(-D-glucopyranosyl)-D-glucopyranose
LactoseThe principle sugar present in milk
5% - 8% in humans, 5% in cow’s milk
D-glucopyranose
OCH2OH
HOOH OH
OHHO
OCH2OH
O
OH
D-galactopyranose
-1,4-glycosidebond
-lactose becausethis OH is betaYes!
•Is this a reducing sugar?
NO
Yes!
4-O-(-D-galactopyranosyl)-D-glucopyranose
Sucrose• Table sugar, obtained from the juice of sugar cane
and sugar beet.
OCH2OH
HOHO
OHO
CH2OH
OH
OH
CH2OH
O
-D-glucopyranose
-D-fructofuranose
-1,2-glycosidebond
-2,1-glycosidebond
No!•Is this a reducing sugar?
NO
No!
1-O-(-D-galactopyranosyl)- - D-fructofurananosideOR
1-O-(- D-fructofurananosyl)- -D-galactopyranoside
N-Glycosides• The anomeric carbon of a cyclic hemiacetal
undergoes reaction with the N-H group of an amine to form an N-glycoside• N-glycosides of the following purine and pyrimidine
bases are structural units of nucleic acids
HN
N
O
O
H
N
N
NH2
O
H
HN
N
O
O
H
CH3
Uracil Thymine Cytosine
N-Glycosides
N
N N
N
NH2
HAdenine
anomericcarbon
a -N-glycosidebond
HH
HOHOCH2
HO OH
NH2
O
N
N
H
HN
N N
NO
HH2N
Guanine
Formation of N-Glycosides(Nucleosides)
• For example, reaction between -D-ribofuranose and cytosine produces water and uridine, one of the structural units of RNA:
OOH
OHOH
HOCH2
N
N
NH2
H
O
+
O
OHOH
HOCH2O
NH2
N
N
-N-glycoside bond
- H2O
-D-Ribofuranose Cytosine
Uridine
anomericcarbon
Gentiobiose• Two glucose
units linked
1-6’.
• Common carbohydrate
branch point
Polysaccharides
• Polysaccharides are chains of five or more monosaccharide:– Starch – a glucose polymer that is the storage carbohydrate
used by plants.– Glycogen – a glucose polymer that is the storage
carbohydrate used by animals.– Cellulose – a glucose polymer that is a major component of
the cell wall in plants & algae.– Agar – natural component of certain seaweed polymer of
galactose & sulfur containing carbohydrates.– Chitin – polymer of glucosamine (a sugar with an amino
functional group).
Starch• Starch is used for energy storage in plants
• it can be separated into two fractions; amylose and amylopectin. Each on complete hydrolysis gives only D-glucose
• amyloseamylose is composed of continuous, unbranched chains of up to 4000 D-glucose units joined by -1,4-glycoside bonds
• amylopectinamylopectin is a highly branched polymer of D-glucose. Chains consist of 24-30 units of D-glucose joined by -1,4-glycoside bonds and branches created by -1,6-glycoside bonds
AmylopectinO
CH2OH
HOOH
O
O
OCH2
HOOH
O
O
OOH
HO
CH2OHO
OCH2OH
HOOH
O
OOH
HO
CH2OHO
Glycogen
• The reserve carbohydrate for animals• a nonlinear polymer of D-glucose units joined
by -1,4- and -1,6-glycoside bonds bonds• the total amount of glycogen in the body of a
well-nourished adult is about 350 g (about 3/4 of a pound) divided almost equally between liver and muscle
Cellulose
• Cellulose is a linear polymer of D-glucose units joined by -1,4-glycoside bonds• it has an average molecular weight of 400,000,
corresponding to approximately 2800 D-glucose units per molecule
Cellulose
Polysaccharides Digestion
Polymers of Glucose
Starch is digestable
Cellulose is not digestable by humans
Modification of Cellulose
• Cellulose Nitrate called guncotton
• Pyroxylin Partially nitrated photographic film and lacquers
• Cellulose Acetate film explosive
• Cellulose reprocessed Rayon via carbon disulfide
Cellulose fibre - Rayon
Cellulose OH Cellulose O-Na+NaOH
Cellulose OCS-Na+
SS C S
Sodium salt of a xanthate ester
H+
spinneretCellulose OH
Cellulose fibre
Membrane Carbohydrates• Membranes of animal plasma cells have large
numbers of relatively small carbohydrates bound to them• these membrane-bound carbohydrates are part of the
mechanism by which cell types recognize each other; they act as antigenic determinantsantigenic determinants
• Early discovery of these antigenic determinants are the blood group substancesblood group substances
• A, B, AB, and O
ABO Blood Classification
• In the ABO system, individuals are classified according to four blood types:
A, B, AB, and O• at the cellular level, the biochemical basis for
this classification is a group of relatively small membrane-bound carbohydrates
ABO Blood Classification
NAGal Gal NAGluCell membrane of erythrocyte
-1,4-) -1,3-) -1-)
Fuc-1,2-)
NAGal = N-acetyl-D-galactosamineGal = D-galactose NAGlu = N-acetyl-D-glucosamine Fuc = L-fucose
missing in type O blood
D-galactose in type B blood
ABO and Disease
A• Syphilis, Smallpox, Bronchial Pneumonia, Rhuematic
Heart DiseaseB
• Infantile Diarrhea, Typhoid Fever, Scarlet FeverC
• Bubonic Plague, Paratyphoid, Scarlet Fever, Cholera
Some infectious disease organisms have ABO antigens on their cell walls conferring resistance to those that can produce the antibodies and increases the susceptibility of those whose blood type matches the antigens.
Glucose Assay• The glucose oxidase method is completely
specific for D-glucose
+
+
glucoseoxidase
D-Gluconic acid
Hydrogen peroxide
-D-Glucopyranose
OHOH
HOHO
CH2 OHO
H2O2
O2 + H2O
CO2H
CH2OH
OHHHHOOHHOHH
‘Chemstrip Kit’Blood glucose test for diabetics
Based on reaction of o-toluidine with glucose
CHO
OHH
HO H
OHH
OHH
CH2OH
H2N
H3C
CH
OHH
HO H
OHH
OHH
CH2OH
N
H3C
peroxidase +colored product +o-toluidine H2O2 H2O
Biosynthesis with Glucose
Cellulose
• Polymer of D-glucose, found in plants.
• Mammals lack the -glycosidase enzyme.
Amylose• Soluble starch, polymer of D-glucose.
• Starch-iodide complex, deep blue.
AmylopectinBranched, insoluble fraction of starch.
Glycogen
• Glucose polymer, similar to amylopectin, but even more highly branched.
• Energy storage in muscle tissue and liver.
• The many branched ends provide a quick means of putting glucose into the blood.
Chitin• Polymer of N-acetylglucosamine.
• Exoskeleton of insects.
Nucleic Acids
• Polymer of ribofuranoside rings linked by phosphate ester groups.
• Each ribose is bonded to a base.
• Ribonucleic acid (RNA)• Deoxyribonucleic acid
(DNA)
Ribonucleosides
A -D-ribofuranoside bonded to a heterocyclic base at the anomeric carbon.
Ribonucleotides
Add phosphate at 5’ carbon.
Structure of RNA
Structure of DNA
-D-2-deoxyribofuranose is the sugar.
• Heterocyclic bases are cytosine, thymine (instead of uracil), adenine, and guanine.
• Linked by phosphate ester groups to form the primary structure.
Base Pairings
Double Helix of DNA
• Two complementary polynucleotide chains are coiled into a helix.
• Described by Watson and Crick, 1953.
DNA Replication
Additional Nucleotides
• Adenosine monophosphate (AMP), a regulatory hormone.
• Nicotinamide adenine dinucleotide (NAD), a coenzyme.
• Adenosine triphosphate (ATP), an energy source.
Amino Acids with Aliphatic R-Groups
Protein Titration CurveAlanine
Common Modifications to Monosaccharides
Deoxy sugars
Amino sugars
Glycosides (acetal)
Deoxy Sugar
Amino Sugar
Glucosamine
HO O
H
H
HO
H
HNH2
H OH
OH
Formation of Glycosides - Acetals
Glycoside: a carbohydrate in which the -OH of the anomeric carbon is replaced by -OR
O
OH
O
OCH3
CH3OH
H+
A ‘glycoside’ bond
A monosaccharide hemiacetal can react with a second molecule of an alcohol to form an acetal
Glycosides
• Glycoside bond: the bond from the anomeric carbon of the glycoside to an -OR group.
• Unlike cyclic hemiacetals, cyclic acetals are not in equilibrium with their open chain carbonyl-containing forms.
• Glycosides do NOT undergo mutarotation.
Naming Glycosides• List the name of the alkyl or aryl group
attached to oxygen followed by the name of the carbohydrate with the ending -e replaced by -ide
– methyl -D-glucopyranoside
– methyl -D-ribofuranoside
Glucopyranoside
Methyl -D-glucopyranoside (methyl -D-glucoside)
O
CH2 OH
H
OH
OCH3()H
HOH
OHH
H
OCH2 OH
HOHO
OHOCH3()
Haworth projectionChair conformation
Disaccharides
Maltose
Lactose
Sucrose
Maltose
• From malt, the juice of sprouted barley and other cereal grains
OHOHO
OH
CH2OH
CH2OH
OHHO
OOH
O
-maltose becausethis -OH is beta
-1,4-glycoside bond
-Maltose
Lactose The principle sugar present in milkabout 5% - 8% in human milk, 4% - 5% in cow’s
milk
D-glucopyranose
OCH2OH
HOOH OH
OHHO
OCH2OH
O
OH
D-galactopyranose
-1,4-glycosidebond
-lactose becausethis OH is beta
-Lactose
Sucrose• Table sugar, obtained from the juice of
sugar cane and sugar beet
OCH2OH
HOHO
OHO
CH2OH
OH
OH
CH2OH
O
-D-glucopyranose
-D-fructofuranose
-1,2-glycosidebond
-2,1-glycosidebond
Sucrose
N-Glycosides• The anomeric carbon of a cyclic hemiacetal
undergoes reaction with the N-H group of an amine to form an N-glycoside• N-glycosides of the following purine and pyrimidine
bases are structural units of nucleic acids
HN
N
O
O
H
N
N
NH2
O
H
HN
N
O
O
H
CH3
Uracil Thymine Cytosine
N-Glycosides
N
N N
N
NH2
HAdenine
anomericcarbon
a -N-glycosidebond
HH
HOHOCH2
HO OH
NH2
O
N
N
H
HN
N N
NO
HH2N
Guanine
Formation of N-Glycosides(Nucleosides)
• For example, reaction between -D-ribofuranose and cytosine produces water and uridine, one of the structural units of RNA:
OOH
OHOH
HOCH2
N
N
NH2
H
O
+
O
OHOH
HOCH2O
NH2
N
N
-N-glycoside bond
- H2O
-D-Ribofuranose Cytosine
Uridine
anomericcarbon
Disaccharides• Three naturally occurring glycosidic linkages:• 1-4’ link: The anomeric carbon is bonded
to oxygen on C4 of second sugar.
• 1-6’ link: The anomeric carbon is bonded to oxygen on C6 of second sugar.
• 1-1’ link: The anomeric carbons of the two sugars are bonded through an oxygen.
Cellobiose
• Two glucose units linked 1-4’.
• Disaccharide of cellulose.
• A mutarotating, reducing sugar.
=>
MaltoseTwo glucose units linked 1-4’.
=>
Lactose• Galactose + glucose linked 1-4’.
• “Milk sugar.”
=>
Gentiobiose• Two glucose units linked 1-6’.
• Rare for disaccharides, but commonly seen as branch point in carbohydrates.
=>
Sucrose• Glucose + fructose, linked 1-1’
• Nonreducing sugar
=>
Polysaccharides• Polysaccharides are chains of five or more monosaccharide:
–Starch – glucose polymer that is the plant storage carbohydrate
–Glycogen – glucose polymer that is the animal storage carbohydrate
–Cellulose – glucose polymer that is a major component of the cell wall in plants & algae.
–Agar – natural component of certain seaweed polymer of galactose & sulfur containing carbohydrates.
–Chitin – polymer of glucosamine (an amino sugar), found in the exoskeleton of bugs.
Starch• Starch is used for energy storage in plants
• Two types: amylose and amylopectin. On complete hydrolysis each type gives only D-glucose
• Amylose: is composed of continuous, unbranched chains of up to 4000 D-glucose units joined by
a-1,4-glycoside bonds
• Amylopectin: is a highly branched polymer of D-glucose. Chains consist of 24-30 units of D-
glucose joined by -1,4-glycoside bonds and branches created by -1,6-glycoside bonds
Amylopectin
OCH2OH
HOOH
O
O
OCH2
HOOH
O
O
OOH
HO
CH2OHO
OCH2OH
HOOH
O
OOH
HO
CH2OHO
Glycogen
• The reserve carbohydrate for animals
• A nonlinear polymer of D-glucose units joined by -1,4- and -1,6-glycoside bonds
bonds.• The total amount of glycogen in the body of a
well-nourished adult is about 350 g (about 3/4 of a pound) divided almost equally between liver and muscle.
Cellulose
• Cellulose is a linear polymer of D-glucose units joined by -1,4-glycoside bonds.
• Average molecular weight of 400,000, corresponds to approximately 2800
D-glucose units per molecule.
Cellulose
OCH2OH
HOOH
O
OOCH2OH
HOOH
OO HO
CH2OH
OH
O
Polysaccharides Digestion
Polymers of Glucose
Starch is digestable
Cellulose is not digestable by humans
Modification of Cellulose
• Cellulose Nitrate guncotton
•Pyroxylin Partially nitrated photographic film
•Cellulose Acetate film
Cellulose fibre - Rayon
Cellulose OH Cellulose O-Na+NaOH
Cellulose OCS-Na+
SS C S
Sodium salt of a xanthate ester
H+
spinneretCellulose OH
Cellulose fibre
Biological Sugars and reactions
Membrane Carbohydrates• Membranes of animal plasma cells have large
numbers of bound small carbohydrates to them.
•these membrane-bound carbohydrates are part of the mechanism by which cell types recognize each other; they act as antigenic determinants
•among the first discovered of these antigenic determinants are the blood group substances
ABO Blood Classification
• at the cellular level, the biochemical basis for this classification is a group of relatively small membrane-bound carbohydrates
ABO Blood Classification
NAGal Gal NAGluCell membrane of erythrocyte
-1,4-) -1,3-) -1-)
Fuc-1,2-)
NAGal = N-acetyl-D-galactosamineGal = D-galactose NAGlu = N-acetyl-D-glucosamine Fuc = L-fucose
missing in type O blood
D-galactose in type B blood
•In the ABO system, individuals are classified according to four blood types: A, B, AB, and O
‘Chemstrip Kit’Blood glucose test for diabetics
Based on reaction of o-toluidine with glucose
CHO
OHH
HO H
OHH
OHH
CH2OH
H2N
H3C
CH
OHH
HO H
OHH
OHH
CH2OH
N
H3C
Glucose Assay
• The o-toluidine test is applied directly to serum, plasma, cerebrospinal fluid, and urine
•Diabetes: A common analytical procedure in the clinical chemistry laboratory is the determination of glucose in blood, urine, or other biological fluid
• glucose reacts with 2-methylaniline (o-toluidine) in the presence of acetic acid to give an imine which has a blue-green color
–the intensity of the absorption at 625 nm is proportional to the glucose concentration
• Galactose, mannose, and to a lesser extent lactose and xylose also react with o-toluidine to give colored imines and, therefore, have the potential for false positive.
samples as small as 20 L (microliters) can be used.
Glucose Assay• The glucose oxidase method is completely
specific for D-glucose
+
+
glucoseoxidase
D-Gluconic acid
Hydrogen peroxide
-D-Glucopyranose
OHOH
HOHO
CH2 OHO
H2O2
O2 + H2O
CO2H
CH2OH
OHHHHOOHHOHH
Glucose Assay
• O2 is reduced to hydrogen peroxide H2O2
• the concentration of H2O2 is proportional to the concentration of glucose in the sample
• in one procedure, hydrogen peroxide is used to oxidize o-toluidine to a colored product, whose concentration is determined spectrophotometrically
peroxidase +colored product +o-toluidine H2O2 H2O
Vitamin C - A monosaccharide?• Vitamin C, vital for life is a necessary part of our
diet because we cannot synthesize it. (Most plants and animals except primates and guinea pigs can make their own Vitamin C).
•It is needed to maintain health of dentine, cartilage, connective tissue and bone.
•Recommended daily allowance ~45mg for adults (60mg if pregnant, 80mg if lactating).
Ascorbic Acid (Vitamin C)• L-Ascorbic acid (vitamin C) is synthesized both
biochemically and industrially from D-glucose
L-ascorbic acidVitamin C
OOHH
CH2OH
O
OHHO
-D-Glucopyranose
O
OHOH
HOHO
CH2OH
Biosynthesis from Glucose
Glycocalyx
The outer viscous covering of fibers extending from a bacterium
composition: The glycocalyx is usually a viscous polysaccharide and polypeptide slime.
Glycocalyx of Intestinal EpitheliumNote that some carbohydrates are covalently attached to membrane components, while others are secreted as extracellular matrix
Fig 16, The Cell, D.W. Fawcett (1981)
Glycocalyx of Lymphocyte
Diagram of Glycocalyx
Cellulose
• Polymer of D-glucose, found in plants.
• Mammals lack the -glycosidase enzyme.
=>
Amylose• Soluble starch, polymer of D-glucose.
• Starch-iodide complex, deep blue.
=>
AmylopectinBranched, insoluble fraction of starch.
Glycogen• Glucose polymer, similar to amylopectin, but
even more highly branched.
•Energy storage in muscle tissue and liver.
•The many branched ends provide a quick means of putting glucose into the blood.
Chitin• Polymer of N-acetylglucosamine.
=>
•Exoskeleton of insects.
Ribonucleosides
A -D-ribofuranoside bonded to a heterocyclic base at the anomeric carbon.
=>
Ribonucleotides
Add phosphate at 5’ carbon.
Nucleic Acids
• Polymer of ribofuranoside rings linked by phosphate esters.
=>
•Each ribose is bonded to a base.
•Ribonucleic acid (RNA)
•Deoxyribonucleic acid (DNA)
Structure of RNA
=>
Structure of DNA
-D-2-deoxyribofuranose is the sugar.
•Heterocyclic bases are cytosine, thymine (instead of uracil), adenine, and guanine.
Linked by phosphate ester groups to form the primary structure.
Base Pairings
=>
Double Helix of DNA
• Two complementary polynucleotide chains are coiled into a helix.
•Described by Watson and Crick, 1953.
DNA Replication
=>
Additional Nucleotides
• Adenosine monophosphate (AMP), a regulatory hormone.
• Nicotinamide adenine dinucleotide (NAD), a coenzyme.
• Adenosine triphosphate (ATP), an energy source.