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18-1Chemistry 121 Winter 2009 LA Tech
Introduction to Organic Chemistry and BiochemistryIntroduction to Organic Chemistry and Biochemistry Instructor Dr. Upali Siriwardane (Ph.D. Ohio State) E-mail: [email protected] Office: 311 Carson Taylor Hall ; Phone: 318-257-4941;Office Hours: MTW 9:00 am - 11:00 am; TR 9::00 - !0:00 am & 1:00-2:00 pm.December 19, Test 1 (Chapters 12-14)January 2 Test 1 (Chapters 15-16)February 6 (Chapters 17-19)February 27, (Chapters 20-22)March 2, 2009, Make Up Exam:Bring Scantron Sheet 882-E
Chemistry 121(01) Winter 2009
18-3Chemistry 121 Winter 2009 LA Tech
Chapter 18: Chapter 18: CarbohydratesCarbohydrates18.1 Biochemistry--An Overview18.2 Occurrence and Functions of Carbohydrates18.3 Classification of Carbohydrates18.4 Chirality: Handedness in Molecules18.5 Stereoisomerism: Enantiomers and Diastereomers18.6 Designating Handedness Using Fischer Projections18.7 Properties of Enantiomers18.8 Classification of Monosaccharides18.9 Biochemically Important Monosaccharides18.10 Cyclic Forms of Monosaccharides18.11 Haworth Projection Formulas18.12 Reactions of Monosaccharides18.13 Disaccharides18.14 General Characteristics of Polysaccharides18.15 Storage Polysaccharides18.16 Structural Polysaccharides18.17 Acidic Polysaccharides18.18 Glycolipids and Glycoproteins18.19 Dietary Considerations and Carbohydrates
18-4Chemistry 121 Winter 2009 LA Tech
BiochemistryBiochemistryBiochemistryBiochemistry is the study of the chemical processes in is the study of the chemical processes in
living organisms. It deals with the structure and function living organisms. It deals with the structure and function of cellular components, such as proteins, carbohydrates, of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules.lipids, nucleic acids, and other biomolecules.
• Carbohydrates • Lipids • Proteins • Nucleic Acids • Use of carbohydrates as an energy source
18-5Chemistry 121 Winter 2009 LA Tech
Occurrence and Functions of CarbohydratesOccurrence and Functions of Carbohydrates
OccurrenceOccurrenceDifferent objects such as sheets of paper, insect skeletons, Different objects such as sheets of paper, insect skeletons,
fruits, cotton fabrics and ropes have one common feature: fruits, cotton fabrics and ropes have one common feature: they all contain carbohydrates.they all contain carbohydrates.
FunctionsFunctionsThe chemical structure of carbohydrates, with their many The chemical structure of carbohydrates, with their many
hydroxyl groups and the ability to assumehydroxyl groups and the ability to assume
various spatial configurations, makes it possible for them to various spatial configurations, makes it possible for them to form nearly unlimited combinationsform nearly unlimited combinations
with other carbohydrate molecules, as well as with proteins with other carbohydrate molecules, as well as with proteins and lipids. The resulting structuresand lipids. The resulting structures
perform important biological functions.perform important biological functions.
18-6Chemistry 121 Winter 2009 LA Tech
Classification of Carbohydrates MonosaccharidesMonosaccharidesThey consist of one sugar containing They consist of one sugar containing 3,4,5,6 and 7 carbon atoms 3,4,5,6 and 7 carbon atoms and are and are
usually colorless, water-soluble, crystalline solids. Some usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides monosaccharides have a sweet taste. Examples of monosaccharides include include glucose (dextrose), fructose (levulose), galactose, xylose and glucose (dextrose), fructose (levulose), galactose, xylose and ribose. ribose.
Disaccharides Disaccharides a sugar (a carbohydrate) composed of two monosaccharides.a sugar (a carbohydrate) composed of two monosaccharides.
OligosaccharideOligosaccharide An oligosaccharide is a saccharide polymer containing a small number
(typically 3-10 monosaccharides
PolysacharidesPolysacharidesAre relatively complex carbohydrates. They are polymers made up of Are relatively complex carbohydrates. They are polymers made up of
many monosaccharides joined together by glycosidic bonds. They many monosaccharides joined together by glycosidic bonds. They are insoluble in water, and have no sweet taste. are insoluble in water, and have no sweet taste.
18-7Chemistry 121 Winter 2009 LA Tech
Chirality: Handedness in MoleculesChirality: Handedness in Molecules
A "chiral" molecule is one that is not superimposable with its mirror image. Like left and right hands that have a thumb, fingers in the same order, but are mirror images and not the same, chiral molecules have the same things attached in the same order, but are mirror images and not the same.
18-8Chemistry 121 Winter 2009 LA Tech
Fischer Projection FormulasFischer Projection FormulasFischer projection:Fischer projection: a two dimensional a two dimensional
representation for showing the configuration of a representation for showing the configuration of a tetrahedral stereocentertetrahedral stereocenter• horizontal lines represent bonds projecting forward • vertical lines represent bonds projecting to the rear• the first and last carbons in the chain are written in full;
others are indicated by the crossing of bonds
CHO
CH OH
CH2OH
CHO
H OH
CH2OH
(R)-Glyceraldehyde
convert to a Fischerprojection
(R)-Glyceraldehyde
18-9Chemistry 121 Winter 2009 LA Tech
Stereoisomerism: Enantiomers and DiastereomersStereoisomerism: Enantiomers and DiastereomersA Fischer projection is the most useful projection for discovering A Fischer projection is the most useful projection for discovering
enantiomers. Compare the Glyceraldehyde enantiomer structures in enantiomers. Compare the Glyceraldehyde enantiomer structures in this diagram. this diagram.
D- and L-MonosaccharidesD- and L-Monosaccharides
CHO
H OH
CH2OH
CHO
CH2OH
HHO
D D
L-GlyceraldehydeD-Glyceraldehyde
[]25 = +13.5° []25 = -13.5°D-monosaccharideD-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the rightL-monosaccharideL-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the left
18-10Chemistry 121 Winter 2009 LA Tech
Properties of EnantiomersProperties of EnantiomersEnantiomers have, when present in a symmetric environment, identical chemical and physical properties
except for their ability to rotate plane-polarized light by equal amounts but in opposite directions. A mixture of equal parts of an optically active isomer and its enantiomer is termed racemic and has a net rotation of plane-polarized light of zero.Enantiomers of each other often do have different chemical properties related to other substances that are also enantiomers. Since many molecules in the bodies of living beings are enantiomers themselves, there is often a marked difference in the effects of two symmetrical enantiomers on living beings, including human beings.
18-12Chemistry 121 Winter 2009 LA Tech
Optically active of enantiomersOptically active of enantiomers
CHO
H OH
CH2OH
CHO
CH2OH
HHO
D D
L-GlyceraldehydeD-Glyceraldehyde
[]25 = +13.5° []25 = -13.5°
18-13Chemistry 121 Winter 2009 LA Tech
D- and L-MonosaccharidesD- and L-MonosaccharidesIn 1891, Emil Fischer made the arbitrary In 1891, Emil Fischer made the arbitrary
assignments of D- and L- to the enantiomers of assignments of D- and L- to the enantiomers of glyceraldehydeglyceraldehyde
CHO
H OH
CH2OH
CHO
CH2OH
HHO
D D
L-GlyceraldehydeD-Glyceraldehyde
[]25 = +13.5° []25 = -13.5°
18-14Chemistry 121 Winter 2009 LA Tech
D- and L-MonosaccharidesD- and L-MonosaccharidesAccording to the conventions proposed by FischerAccording to the conventions proposed by Fischer
• D-monosaccharideD-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the right
• L-monosaccharideL-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the left
18-15Chemistry 121 Winter 2009 LA Tech
D- and L-MonosaccharidesD- and L-MonosaccharidesFollowing are Following are
• the two most common D-aldotetroses and • the two most common D-aldopentoses
D-Erythrose D-Threose D-Ribose 2-Deoxy-D-ribose
CH2OH
CHO
OH
OHH
H
CH2OH
CHO
OH
HHO
H
CH2OH
CHO
OH
OHH
H
CH2OH
CHO
OH
HH
H
OHH OHH
18-16Chemistry 121 Winter 2009 LA Tech
D- and L-MonosaccharidesD- and L-Monosaccharides• and the three common D-aldohexoses
CHO
H
OHH
HO
OHH
D-GlucosamineD-Glucose D-Galactose
CH2OH
OHH
CHO
H
OHH
HO
HHO
CH2OH
OHH
CHO
H
NH2H
HO
OHH
CH2OH
OHH
18-17Chemistry 121 Winter 2009 LA Tech
D- and L-MonosaccharidesD- and L-MonosaccharidesAmino sugarsAmino sugars
• N-acetyl-D-glucosamine is a component of many polysaccharides, including connective tissue such as cartilage; it is also a component of chitin, the hard shell-like exoskeleton of lobsters, crabs, and shrimp
CHO
OH
OH
H
NH2
H
H
HO
H
CH2OH
CHO
OH
OH
H
H
H
H
HO
H2N
CH2OH
CHO
OH
OH
H
NHCCH3
H
H
HO
H
CH2OH
OCHO
OH
H
H
NH2
H
HO
HO
H
CH2OH
4
2
D-Mannosamine(C-2 stereoisomer of D-glucosamine)
D-Glucosamine D-Galactosamine(C-4 stereoisomer of D-glucosamine)
N-Acetyl-D-glucosamine
18-18Chemistry 121 Winter 2009 LA Tech
Classification of MonosaccharidesMonosaccharides have the general formula CCnnHH2n2nOOnn
the most common have from 3 to 9 carbons
Triose (3) , tetrose(4), pentose(5), hexose(6)
• aldosealdose: a monosaccharide containing an aldehyde group: E.g. D-glucose
• ketoseketose: a monosaccharide containing a ketone group: E.g. D-Fructose
18-19Chemistry 121 Winter 2009 LA Tech
Carbohydrates: MonosaccharidesCarbohydrates: MonosaccharidesCarbohydrate:Carbohydrate: a polyhydroxy aldehyde, a polyhydroxy a polyhydroxy aldehyde, a polyhydroxy
ketone, or a polymeric substance that gives these ketone, or a polymeric substance that gives these compounds on hydrolysiscompounds on hydrolysis
Monosaccharide:Monosaccharide: a carbohydrate that cannot be hydrolyzed a carbohydrate that cannot be hydrolyzed to a simpler carbohydrateto a simpler carbohydrate
• monosaccharides have the general formula CCnnHH2n2nOOnn
• the most common have from 3 to 9 carbons• aldosealdose: a monosaccharide containing an aldehyde
group: E.g. D-glucose • ketoseketose: a monosaccharide containing a ketone group:
E.g. D-Fructose
18-20Chemistry 121 Winter 2009 LA Tech
MonosaccharidesMonosaccharides• monosaccharides are classified by their number of
carbon atoms
hexose
heptoseoctose
triosetetrosepentose
FormulaNameC3H6O3C4H8O4
C5H10 O5
C6H12 O6
C7H14 O7C8H16 O8
18-21Chemistry 121 Winter 2009 LA Tech
Aldoses: Trioses, Tetroses and PentosesAldoses: Trioses, Tetroses and Pentoses
18-24Chemistry 121 Winter 2009 LA Tech
MonosaccharidesMonosaccharides• there are only two trioses
• often aldo- and keto- are omitted and these compounds are referred to simply as trioses
• although this designation does not tell the nature of the carbonyl group, it at least tells the number of carbons
CHO
CHOH
CH2OH
CH2OH
C=O
CH2OH
Dihydroxyacetone (a ketotriose)
Glyceraldehyde (an aldotriose)
18-25Chemistry 121 Winter 2009 LA Tech
MonosaccharidesMonosaccharidesGlyceraldehyde contains a stereocenter and exists Glyceraldehyde contains a stereocenter and exists
as a pair of enantiomersas a pair of enantiomers
CHO
CH OH
CH2OH
CHO
C
CH2OH
HHO
(S)-Glycer-aldehyde
(R)-Glycer-aldehyde
18-28Chemistry 121 Winter 2009 LA Tech
Intramolecular cyclization• Simple sugars tend to exist primarily
in cyclic form through hemiacetal or hemiketal formation. It is the most
stable arrangement.
C
C
C
CH2OH
C
C
OH
O
H C
C
C
CH2OH
C
C
O
OH
aldehyde hemiacetal
18-29Chemistry 121 Winter 2009 LA Tech
Intramolecular cyclization
• The -OH group that forms can be above or below the ring resulting in two forms -
anomers anomers and and are used to identify the two are used to identify the two
formsforms..
- OH group is down compared to CH2OH (trans).
- OH group is up compared to CH2OH (cis).
18-30Chemistry 121 Winter 2009 LA Tech
Cyclization of D-glucose--DD - glucose - glucose
- - DD - glucose - glucose
H
OH
O H
OHOH
H
OHH
OH
CH 2 OH
H
C
C
C
C
C
CH 2 OH
OH
OH
H
OHH
HO
H
H
OH
OH
OH
OHOH
H
H
H
OH
CH 2 OH
H
OH
18-32Chemistry 121 Winter 2009 LA Tech
Haworth ProjectionsHaworth Projections• the anomers of D-glucopyranose
CHO
OH
H
OH
H
HO
H
H OH
CH2OH
HH OH
HHO
HOH
OH
H
CH2OHO
C
OH
HHO
HOH
H
CH2OHOH
O
H
OHH OH
HHO
HH
OH
H
CH2OHO
D-Glucose
-D-Glucopyranose (-D-Glucose)
()
()
-D-Glucopyranose (-D-Glucose)
anomeric carbon
+
anomericcarbon
5
5
1
1
redraw to show the -OH on carbon-5 close to thealdehyde on carbon-1
H
18-33Chemistry 121 Winter 2009 LA Tech
Haworth ProjectionsHaworth Projections• 5- and 6-membered hemiacetals are represented as
planar pentagons or hexagons viewed through the edge
• most commonly written with the anomeric carbon on the right and the hemiacetal oxygen to the back right
• -- means that -OH on the anomeric carbon is cis to the terminal -CH2OH; -- means it is trans
• a 6-membered hemiacetal is shown by the infix -pyranpyran- • a 5-membered hemiacetal is shown by the infix -furanfuran-
OOPyranFuran
18-34Chemistry 121 Winter 2009 LA Tech
Cyclic StructuresCyclic StructuresAldopentoses also form cyclic hemiacetalsAldopentoses also form cyclic hemiacetals
• the most prevalent forms of D-ribose and other pentoses in the biological world are furanoses
• the prefix deoxy- means “without oxygen”
OH ()
H
HOH OH
H HOHOCH2
H
OH ()
HOH H
H HOHOCH2
-D-Ribofuranose(-D-Ribose)
-2-Deoxy-D-ribofuranose(-2-Deoxy-D-ribose)
18-35Chemistry 121 Winter 2009 LA Tech
Cyclic StructuresCyclic StructuresD-Fructose, a 2-ketohexose, also forms a cyclic D-Fructose, a 2-ketohexose, also forms a cyclic
hemiacetalhemiacetal
O
HO
HOCH2H
HHO
CH2OH
OHH
OH
HO
HOCH2H
HHO
H
HHO
HOHOHOCH2
CH2OH
O
HCH2OH
OH5
5
1
2
2
()
-D-Fructofuranose(-D-Fructose)
-D-Fructofuranose(-D-Fructose)
()
1
anomericcarbon
5
1
2
18-36Chemistry 121 Winter 2009 LA Tech
Conformational FormulasConformational Formulas• five-membered rings are close to planar so that
Haworth projections are adequate to represent furanoses
O
OH()
H
HHO OH
H H
-D-Ribofuranose(-D-Ribose)
O
H
OH()
HHO OH
H H
-D-Ribofuranose(-D-Ribose)
HOCH2 HOCH2
18-37Chemistry 121 Winter 2009 LA Tech
Conformational FormulasConformational Formulas• the six-membered rings of pyranoses are more
accurately represented as chair conformations
OH
HO
H
HO
H
HOHH
OH
OH
OHH
HO
H
HO
H
HOHH
O
OH
OH
HO
H
HO
H
OHOHH
H
OH
OH
H
HO
H
HO
H
OOHH
H
OH
-D-Glucopyranose(-D-Glucose)[]D = +18.7°
-D-Glucopyranose(-D-Glucose)[]D = +112°
rotate aboutC-1 to C-2 bond
18-38Chemistry 121 Winter 2009 LA Tech
Conformational FormulasConformational Formulas• compare the orientations of groups on carbons 1-5 in
the Haworth and chair representations of -D-glucopyranose
• in each case, beginning at carbon 1, they are up-down-up-down-up
OCH2OH
HOHO
OHOH()H
H OH
HHO
HOH()
OH
H
CH2OHO
-D-Glucopyranose(chair conformation)
-D-Glucopyranose(Haworth projection)
123
4
5
6
1
23
4
5
6
18-39Chemistry 121 Winter 2009 LA Tech
MutarotationMutarotationMutarotation:Mutarotation: the change in specific rotation that the change in specific rotation that
occurs when the occurs when the or or forms of a carbohydrate forms of a carbohydrate are converted to an equilibrium mixture of the twoare 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)
18-40Chemistry 121 Winter 2009 LA Tech
MutarotationMutarotationmutarotation of glucosemutarotation of glucose
[]D25 +18.7°
-D-Glucopyranose
-D-Glucopyranose
Open-chain form
()
()
[]D25 +112°
OHOH
HOHO
CH2OH
OCH2OH
O
HOHO
HOOH
OHO
C
CH2OHHO
HO
HO H
18-41Chemistry 121 Winter 2009 LA Tech
Fischer & Haworth ProjectionFischer & Haworth ProjectionIn solutions less than 1% of a sugar will be in the In solutions less than 1% of a sugar will be in the
linear form shown as Fischer projectionlinear form shown as Fischer projection
The normal form of most sugars is in a cyclic The normal form of most sugars is in a cyclic hemiacetal form shown as Haworth projectionhemiacetal form shown as Haworth projection
18-42Chemistry 121 Winter 2009 LA Tech
Converting Fischer to Haworth Converting Fischer to Haworth ProjectionProjection
18-46Chemistry 121 Winter 2009 LA Tech
Two monsaccharides connected by a bridging O atom called a glycosidic bond as
in sucrose.
18-50Chemistry 121 Winter 2009 LA Tech
Polysaccharides
• These are biopolymers composed of hundreds to thousands of simple sugar units (monosaccharides).
• The most common monosaccharide used
in polysaccharides is glucose.
C
C
C
C
C
CH 2 OH
OH
OH
H
OHH
HO
H
H
OH
18-51Chemistry 121 Winter 2009 LA Tech
Polysaccharides
• Uses for polysaccharidesUses for polysaccharides
• Storage polysaccharidesStorage polysaccharides
• Energy storage - starch and glycogen
• Structural polysaccharidesStructural polysaccharides
• Used to provide protective walls or lubricative coating to cells -
cellulose and mucopolysaccharides.
• Structural peptidoglycansStructural peptidoglycans
• Bacterial cell walls
18-52Chemistry 121 Winter 2009 LA Tech
Starch• Energy storage used by plants
• Long repeating chain of -D-glucose
• Chains up to 4000 units
• AmyloseAmylose straight chain
• AmylopectinAmylopectin branched structure
• Starch is a mixture of about 75% amylopectin and 25% amylose.
18-53Chemistry 121 Winter 2009 LA Tech
Amylose starch
• Straight chain that forms coils (1 4) linkage.
O
O
H
HOH
OH
CH2OH
OOH
OHH
HO
HOH2C
O OH
OH
H
HO
HOH2C
O
O
HOH
HHO
HOH2C
O
O
H
HO
H
OH
CH2OH
O
OH
OHH
OH
CH2OH
O
O
HHO
HOH
CH2OH
18-54Chemistry 121 Winter 2009 LA Tech
Amylose starch
Example showing coiled structure - 12 glucose units
- hydrogens and side chains are omitted.
18-55Chemistry 121 Winter 2009 LA Tech
Amylopectin starch• Amylopectin differs from amylose only in
that it has side chains. These are formed from
(1 6) links
• Side chains occur every 24-30 units.• Starch is stored as starch grains. They cannot diffuse from the cell and have little effect on the osmotic pressure of the cell.
18-57Chemistry 121 Winter 2009 LA Tech
Glycogen• Energy storage of animals.
• Stored in liver and muscles as granules.
• Similar to amylopectin but more highly branched.
O
O
O
O
O
O
O
O
O
O
O
O
O
Oc
(1 6) linkageat crosslink
c
18-58Chemistry 121 Winter 2009 LA Tech
Cellulose
• Most abundant polysaccharide.
• (1 4) glycosidic linkages.
• Result in long fibers - for plant structure.
O O
H
OHH
OH
CH2OH
O OCH2OH
OHH
HO HO O
H
OHH
OH
CH2OH
O OCH2OH
OHH
HO HO O
H
OHH
OH
CH2OH
OCH2OH
OHH
HO H
18-59Chemistry 121 Winter 2009 LA Tech
H OO
HH
OHH
COO-
HO
H O
OH
O
HH
NH
CH2OH
H
C OCH3
H OO
HH
OHH
COO-
HO
H O
OH HH
NH
CH2OH
H
C OCH3
H OO
HH
OHH
COO-
HO
H O
OH
O
HH
NH
CH2OH
H
C OCH3O
Mucopolysaccharides• These materials provide a thin, viscous,
jelly-like coating to cells.
• The most abundant form ishyaluronic acid.
• Alternating units of• N-
acetylglucosamine • and D-glucuronic
acid.
(1 3)
(1 4)
18-64Chemistry 121 Winter 2009 LA Tech
Cyclic StructureCyclic StructureMonosaccharides have hydroxyl and carbonyl Monosaccharides have hydroxyl and carbonyl
groups in the same molecule and exist almost groups in the same molecule and exist almost entirely as five- and six-membered cyclic entirely as five- and six-membered cyclic hemiacetalshemiacetals• anomeric carbonanomeric carbon: the hemiacetal carbon of a cyclic
form of a monosaccharide• anomersanomers: monosaccharides that differ in configuration
only at their anomeric carbons
18-65Chemistry 121 Winter 2009 LA Tech
GlycosidesGlycosidesGlycosideGlycoside: : a carbohydrate in which the -OH on its a carbohydrate in which the -OH on its
anomeric carbon is replaced by -ORanomeric carbon is replaced by -OR
HH OH
HHO
HOH
OH
H
CH2OHO
CH3OH H+
-H2O
OCH2OH
H
OH
OCH3H
HOH
OHH
H
OCH2OH
H
OH
HH
HOH
OHH
OCH3
(-D-Glucose)-D-Glucopyranose
Methyl -D-glucopyranoside(Methyl -D-glucoside)
anomeric carbon
+
+
Methyl -D-glucopyranoside(Methyl -D-glucoside)
glycosidicbond glycosidic
bond
18-66Chemistry 121 Winter 2009 LA Tech
GlycosidesGlycosidesGlycosidic bond:Glycosidic bond: the bond from the anomeric the bond from the anomeric
carbon of the glycoside to an -OR groupcarbon of the glycoside to an -OR group
To name a glycoside, name the alkyl or aryl group To name a glycoside, name the alkyl or aryl group bonded to oxygen followed by the name of the bonded to oxygen followed by the name of the carbohydrate; replace the ending carbohydrate; replace the ending -e-e by by -ide-ide• methyl -D-glucopyranoside• methyl -D-ribofuranoside
18-67Chemistry 121 Winter 2009 LA Tech
NN-Glycosides-Glycosides• the anomeric carbon of a cyclic hemiacetal also reacts
with an N-H of an amine to form an N-glycoside• especially important in the biological world are the N-
glycosides of D-Ribose and 2-deoxy-D-ribose with the following heterocyclic aromatic amines
HN
NH
O
O
Uracil
N
NH
O
NH2
Cytosine
HN
NH
O
O
Thymine
CH3N
N N
N
H
NH2
HN
N N
N
H
O
H2N
Adenine Guanine
Pyrimidine bases Purine bases
18-68Chemistry 121 Winter 2009 LA Tech
NN-Glycosides-Glycosides• following is the -N-glycoside formed between D-
ribofuranose and cytosine
H
H
H
H
OHOCH2
HO OH
NH2
O
N
N
anomericcarbon
a -N-glycosidicbond
18-69Chemistry 121 Winter 2009 LA Tech
Reduction to AlditolsReduction to AlditolsThe carbonyl group of a monosaccharide can be The carbonyl group of a monosaccharide can be
reduced to an hydroxyl group by a variety of reduced to an hydroxyl group by a variety of reducing agents, including NaBHreducing agents, including NaBH44
OHOH
HOHO
CH2OHO
CHOOHHHHOOHH
CH2OHOHH
NaBH4
CH2OHOHHHHOOHH
CH2OHOHH
D-Glucitol(D-Sorbitol)
D-Glucose-D-Glucopyranose
18-70Chemistry 121 Winter 2009 LA Tech
Reduction to AlditolsReduction to Alditols• name alditols by replacing the --oseose of the name of the
monosaccharide by -itol-itol• sorbitol is found in the plant world in many berries and
in cherries, plums, pears, apples, and seaweed; it is about 60% as sweet as sugar
• other common alditols include
CH2OH
CH2OH
OHHOHH
CH2OH
CH2OH
OHHHHOOHH
CH2OHHHOHHOOHH
CH2OHOHH
D-Mannitol XylitolErythritol
18-71Chemistry 121 Winter 2009 LA Tech
Oxidation to Aldonic AcidsOxidation to Aldonic AcidsThe -CHO group can be oxidized to -COOHThe -CHO group can be oxidized to -COOH
• reducing sugar:reducing sugar: any carbohydrate that reacts with an oxidizing agent to form an aldonic acid
oxidizingagent
D-GluconateD-Glucose
C
OHH
HHO
OHH
CH2OH
OHH
O HC
OHH
HHO
OHH
CH2OH
OHH
O O--D-Glucopyranose(-D-Glucose)
OCH2OH
HOHO
OHOH
basicsolution
18-72Chemistry 121 Winter 2009 LA Tech
Oxidation to Uronic AcidsOxidation to Uronic AcidsEnzyme-catalyzed oxidation of the 1° alcohol at Enzyme-catalyzed oxidation of the 1° alcohol at
carbon-6 of a hexose gives a uronic acidcarbon-6 of a hexose gives a uronic acid
CHO
CH2OH
OHHHHOOHHOHH
CHO
COOH
OHHHHOOHHOHH
HOHO
OHOH
COOHO
D-Glucose
enzyme-catalyzedoxidation
D-Glucuronic acid(a uronic acid)
18-73Chemistry 121 Winter 2009 LA Tech
Oxidation to Uronic AcidsOxidation to Uronic Acids• the body uses glucuronic acid to detoxify foreign
alcohols and phenols• these compounds are converted in the liver to
glycosides of glucuronic acid and then excreted in the urine
• the intravenous anesthetic propofol is converted to the following water-soluble glucuronide and excreted
O
OHOHO
OH
COO-
HO
Propofol A urine-soluble glucuronide
18-74Chemistry 121 Winter 2009 LA Tech
Glucose AssayGlucose AssayThe analytical procedure most often performed in The analytical procedure most often performed in
the clinical chemistry laboratory is the the clinical chemistry laboratory is the determination of glucose in blood, urine, or other determination of glucose in blood, urine, or other biological fluidbiological fluid• this need arises because of the high incidence of
diabetes in the population
18-75Chemistry 121 Winter 2009 LA Tech
Glucose AssayGlucose AssayThe glucose oxidase method is completely specific The glucose oxidase method is completely specific
for D-glucosefor D-glucose
+
+
glucoseoxidase
D-Gluconic acid
Hydrogen peroxide
-D-Glucopyranose
OHOH
HOHO
CH2 OHO
H2 O2
O2 + H2O
CO2H
CH2OH
OHHHHOOHHOHH
18-76Chemistry 121 Winter 2009 LA Tech
Glucose AssayGlucose 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
NH2
CH3
H2O2peroxidase colored product+
2-Methylaniline(o-Toluidine)
18-77Chemistry 121 Winter 2009 LA Tech
Ascorbic Acid (Vitamin C)Ascorbic Acid (Vitamin C)L-Ascorbic acid (vitamin C) is synthesized both L-Ascorbic acid (vitamin C) is synthesized both
biochemically and industrially from D-glucosebiochemically and industrially from D-glucose
CHO
CH2OH
OHHHHOOHHOHH
CH2OH
OHH
HHO
O
OH
O
D-Glucose
both biochemialand industrial
syntheses
L-Ascorbic acid (Vitamin C)
18-78Chemistry 121 Winter 2009 LA Tech
Ascorbic Acid (Vitamin C)Ascorbic Acid (Vitamin C)• L-ascorbic acid is very easily oxidized to L-
dehydroascorbic acid • both compounds are physiologically active and are
found in most body fluids
CH2OH
OHH
HHO
O
OH
O
CH2OH
OHH
HO
O
O
O
L-Ascorbic acid (Vitamin C)
L-Dehydroascorbic acid
oxidation
reduction
18-79Chemistry 121 Winter 2009 LA Tech
SucroseSucroseTable sugar, obtained from the juice of sugar cane Table sugar, obtained from the juice of sugar cane
and sugar beetand sugar beet
O
HOOH
OH
CH2OH
O
HO
HOO
CH2OH
HOCH2
OHO
HO
O
OH
CH2OH
HO
HOO
CH2OH
HOCH2
1
1
2
1
2
1
-1,2-glycosidicbond
Sucrose
a unit of -D-glucopyranose
a unit of -D-fructofuranose
18-80Chemistry 121 Winter 2009 LA Tech
LactoseLactoseThe principle sugar present in milkThe principle sugar present in milk
• about 5 - 8% in human milk, 4 - 5% in cow’s milk
OHO
HOOH
O
CH2OH
O
HOOH
OH
CH2OH
OHO O
OH
OH
CH2OH
O OH
OH
OH
CH2OH
1
1
4 4
-1,4-glycosidic bond
-1,4-glycosidic bond
18-81Chemistry 121 Winter 2009 LA Tech
MaltoseMaltoseFrom malt, the juice of sprouted barley and other From malt, the juice of sprouted barley and other
cereal grainscereal grains
OHO
HOOH
OOHO OH()
OH
CH2OH
CH2OHO
OH
O
OHHO
O OH()
HO
OH
CH2OH
HOCH2 14
-1,4-glycosidic bond
1 4
18-82Chemistry 121 Winter 2009 LA Tech
Blood Group SubstancesBlood Group SubstancesMembranes of animal plasma cells have large Membranes of animal plasma cells have large
numbers of relatively small carbohydratesnumbers of relatively small carbohydrates• these membrane-bound carbohydrates are part of the
mechanism by which cell types recognize each other; they act as antigenic determinantsantigenic determinants
• among the first discovered of these antigenic determinants are the blood group substancesblood group substances
In the ABO system, individuals are classified In the ABO system, individuals are classified according to four blood types: A, B, AB, and Oaccording 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
18-83Chemistry 121 Winter 2009 LA Tech
Blood Group SubstancesBlood Group Substances• one of these membrane-bound monosaccharides is L-
fucose
HHO
OHH
CH3
CHO
OHH
HHO
An L-monosaccharide;this -OH is on the left inthe Fischer projection
L-Fucose
Carbon 6 is -CH3 ratherrather than -CH2OH
18-84Chemistry 121 Winter 2009 LA Tech
Blood Group SubstancesBlood Group SubstancesA, B, AB, and O blood typesA, B, AB, and O blood types
N-Acetyl-D-galactosamine
D-Galactose N-Acetyl-D-glucosamine
D-Galactose N-Acetyl-D-glucosamine
Redblood cell
Type A
Type B
D-GalactoseType O N-Acetyl-D-glucosamine
Redblood cell
Redblood cell
D-galactose
(-1,4)
(-1,4)
(-1,3)
(-1,3)
(-1,3)
L-Fucose
(-1,2)
L-Fucose
(-1,2)
L-Fucose
(-1,2)
18-85Chemistry 121 Winter 2009 LA Tech
StarchStarchStarch is used for energy storage in plantsStarch is used for energy storage in plants
• it can be separated into two fractions; amylose and amylopectin
• amyloseamylose is composed of unbranched chains of up to 4000 D-glucose units joined by -1,4-glycosidic bonds
• amylopectinamylopectin is a highly branched polymer of D-glucose; chains consist of 24-30 units of D-glucose joined by -1,4-glycosidic bonds and branches created by -1,6-glycosidic bonds
18-87Chemistry 121 Winter 2009 LA Tech
GlycogenGlycogenThe reserve carbohydrate for animalsThe reserve carbohydrate for animals
• a nonlinear polymer of D-glucose units joined by -1,4- and -1,6-glycosidic 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
18-88Chemistry 121 Winter 2009 LA Tech
CelluloseCelluloseCellulose is a linear polymer of D-glucose units Cellulose is a linear polymer of D-glucose units
joined by joined by -1,4-glycosidic bonds-1,4-glycosidic bonds• it has an average molecular weight of 400,000,
corresponding to approximately 2800 D-glucose units per molecule
• both rayon and acetate rayon are made from chemically modified cellulose