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Transcript of Gülüzar Özbolat_Karbohidratlar
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Chapter 14 Carbohydrates
14.1
Carbohydrates
Copyright 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Carbohydrates
Carbohydrates are
A major source of energyfrom our diet.
Composed of the elementsC, H, and O.
Also called saccharides,which means sugars.
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Carbohydrates
Carbohydrates
Are produced by photosynthesisin plants.
Such as glucose are synthesizedin plants from CO2, H2O, andenergy from the sun.
Are oxidized in living cells(respiration) to produce CO
2,
H2O, and energy.
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Types of Carbohydrates
The types of carbohydrates are
Monosaccharides, the simplest carbohydrates.
Disaccharides, which consist of two monosaccharides.
Polysaccharides, which contain manymonosaccharides.
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Monosaccharides
Monosaccharides consist of
3 to 6 carbon atoms, typically.
A carbonyl group (aldehyde or ketone).
Several hydroxyl groups.
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Aldoses
Aldoses are monosaccharides
With an aldehyde group.
With many hydroxyl (OH)
groups.triose(3 C atoms)
tetrose(4 C atoms)
pentose(5 C atoms)
hexose(6 C atoms)
O
CH aldose
HCOH
HCOH
CH2OH
Erythose, an aldotetrose
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Ketoses
Ketoses are monosaccharides
With a ketone group.
With many hydroxyl (OH)
groups.triose(3 C atoms)
tetrose(4 C atoms)
pentose(5 C atoms)
hexose(6 C atoms)
CH2OH
C=O ketose
HCOH
HCOH
HCOHCH2OH
Fructose, a ketohexose
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Learning Check
Identify each as aldo- or keto- and as tetrose, pentose,
or hexose:
A B
H
CH2OH
OHC
H
H
H
OH
OH
OH
C
C
CHC
O
CH2OH
HHO
CH2OH
O
H OHC
C
C
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Solution
A. aldohexose
B. ketopentose
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14.2
Structures of Monosaccharides
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Fischer Projections
A Fischer projection
Is used to represent carbohydrates.
Places the most oxidized group at the top.
Shows chiral carbons as the intersection of verticaland horizontal lines.
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D and L Notations
In a Fischer projection, the OH group on the Chiral carbon farthest from the carbonyl group
determines an L or D isomer.
Left is assigned the letter Lfor the L-isomer.
Right is assigned the letter Dfor the D-isomer.
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Examples of D and L Isomers of
Monosaccharides
O
CH2OH
H OH
H OH
HO HOHH
C H
CH2OH
H OH
H OH
OHHHC
OH
O
CH2OH
HO H
H OH
H OH
HHO
C
D-glucose D-ribose L-galactose
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Learning Check
Identify each as the D or L isomer.
A. B. C.
__-ribose __- threose __- fructose
CH2OHHO H
HO H
HHO
O
C H
CH2OHHO H
OHH
O
C H
CH2OH
H OH
H OH
HO H
O
CH2OH
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Solution
Identify each as the D or L isomer.
A. B. C.
L-ribose L-threose D-fructose
CH2OH
HO H
HO H
HHO
O
C H
CH2OH
HO H
OHH
O
C H
CH2OH
H OH
H OH
HO HO
CH2OH
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D-Glucose
D-glucose is
Found in fruits, cornsyrup, and honey.
An aldohexose with
the formula C6H12O6. Known as blood sugar
in the body.
The monosaccharide
in polymers of starch,cellulose, andglycogen. Copyright 2007 by Pearson Education, Inc
Publishing as Benjamin Cummings
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Blood Glucose Level
In the body,
Glucose has anormal bloodlevel of 70-90
mg/dL. A glucose
tolerance testmeasures blood
glucose forseveral hoursafter ingestingglucose.
Copyright 2007 by Pearson Education, Inc Publishing as BenjaminCummings
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D-Fructose
D-fructose
Is a ketohexoseC6H12O6.
Is the sweetestcarbohydrate.
Is found in fruitjuices and honey.
Converts toglucose in thebody.
H OH
CH2OH
C
HOH OH
HC
O
C
C
CH2OH
D-FructoseCopyright 2007 by Pearson Education, IncPublishing as Benjamin Cummings
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D-Galactose
D-galactose is
An aldohexose C6H12O6.
Not found free in nature.
Obtained from lactose, adisaccharide.
A similar structure toglucose except for the
OH on C4.
H
H
H OH
CH2OH
C
HO
HO HC
OH
C
C
O
C H
D-Galactose
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Learning Check
Draw the structure and Fischer projection of D-fructose.
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Solution
CH2OHC=O
HO H
H OH
H OHCH2OH
Fischer projection
H OH
CH2OH
C
HOH OH
HC
O
C
C
CH2OH
D-Fructose
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14.3
Cyclic Structures ofMonosaccharides
OH
OH
OHOH
CH2OH
O
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Cyclic Structures
Cyclic structures
Are the prevalent form of monosaccharides with 5 or6 carbon atoms.
Form when the hydroxyl group on C-5 reacts with thealdehyde group or ketone group.
O O
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Cyclic Haworth Structures
Stable cyclic hemiacetals form
When the C=O group and the
OH are part of the samemolecule.
For hexoses, the hydroxyl groupon C-5 reacts with the aldehydegroup or ketone group.
The cyclic structure of a D-isomerhas the last CH2OH grouplocated above the ring.
CH2OHO
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Drawing the Cyclic Structure for
Glucose
STEP 1 Number the carbon chain and turn clockwise toform a linear open chain.
HHO
H
CH2OH
OHCH
H
OH
OH
C
C
C
OH
C1
2
3
4
5
6
6 5 4 3 2 1
H
OHH
OH
C
H H
OH OH
C C C
H
O
CHOCH2
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Cyclic Structure for Glucose
STEP 2 Bend the chain tomake a hexagon
Bond the C5O to C1. Place the C6 group above
the ring.
Write theOH groups onC2 and C4 below the ring.
Write the
OH group on C3above the ring.
Write a newOH on C1.
6
5
4 1
3 2 OH
OH
OHOH
CH2OH
O
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Cyclic Structure for Glucose (cont)
-D-glucose -D-glucose
STEP 3 The newOH on C1 is drawn Down for the anomer. Up for the anomer.
O
CH2OH
OH
OH
OH
OH
O
CH2OH
OH
OH
OH
OH
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Summary of the Formation of Cyclic
Glucose
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-D-Glucose and -D-Glucose inSolution
When placed in solution,
Cyclic structures open and close.
-D-glucose converts to -D-glucose and back.
There is only a small amount of open chain.
-D-glucose D-glucose (open) -D-glucose
(36%) (trace) (64%)
OH
OH
OHOH
CH2OH
OOH
OH
OHOH
CH2OH
OOH
CH2OH
OH
OC
H
OH
OH
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Cyclic Structure of Fructose
Fructose Is a ketohexose.
Forms a cyclic structure.
Reacts the OH on C-5 with the C=O on C-2.
D-fructose -D-fructose-D-fructose
OCH
2OH
OH
OH
OH
CH2OH
OOH
CH2
OH
OH
OH
CH2OH
H OH
H OH
HHO
O
CH2OH
C
C
C
C
CH2OH
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Learning Check
Write the cyclic form of -D-galactose
H
H
H OH
CH2OH
C
HO
HO HC
OH
C
C
O
C H
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Solution
-D-galactose
OH
OH
OH
OH
CH2OH
O
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14.4Chemical Properties of
Monosaccharides
Copyright 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Reducing Sugars
Reducing sugars
Are monosaccharides with a carbonyl group thatoxidizes to give a carboxylic acid.
Undergo reaction with Benedicts reagent (Cu2+) to
give the corresponding carboxylic acid.
Include the monosaccharides glucose, galactose,and fructose.
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Oxidation of D-Glucose
+ Cu2O(s)
D-gluconic acidD-glucose
+ Cu2+
H OH
H OH
HHO
H OH
O
OH
CH2OH
C
C
C
C
C
H OH
H OH
HHO
H OH
O
H
CH2OH
C
C
C
C
C
[O]
Benedictsreagent
Glucose is a reducingsugar
Cu
+
(reducedform)
Glucose is oxidizedto a carboxylic acid
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Reduction of Monosaccharides
The reduction ofmonosaccharides
Involves the carbonylgroup.
Produces sugaralcohols called alditols.
Such as D-glucosegives D-glucitol alsocalled sorbitol.
D-Glucitol
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Learning Check
Write the products of the oxidation and reduction of
D-mannose.
H
O
CH2OH
H OH
H OH
HO H
HHO
C
D-mannose
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Solution
Write the products of the oxidation and reduction of
D-mannose.
H
O
CH2OHH OH
H OH
HO H
HHO
COH
O
CH2OH
H OH
H OH
HO H
HHO
C
CH2OH
H OH
H OH
HO H
HHO
CH2OH
Reduction Oxidation
D-mannitol D-mannose D-mannonic acid
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14.5 Disaccharides
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Important Disaccharides
A disaccharide
Consists of two monosaccharides.
Monosaccharides Disaccharide
Glucose + glucose maltose + H2OGlucose + galactose lactose + H2OGlucose + fructose sucrose + H2O
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Maltose
Maltose is
A disaccharide also known as malt sugar.
Composed of two D-glucose molecules.
Obtained from the hydrolysis of starch. Linked by an -1,4-glycosidic bond formed from the
OH on C1 of the first glucose and OH on C4 ofthe second glucose.
Used in cereals, candies, and brewing.
Found in both the - and - forms.
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Formation of Maltose
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Lactose
Lactose
Is a disaccharide of -D-galactose and - or-D-glucose.
Contains a -1,4-glycosidic bond.
Is found in milk andmilk products.
-form
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Sucrose
Sucrose or table sugar
Is obtained from sugar cane and sugar beets.
Consists of -D-glucose and -D-fructose..
Has an ,-1,2-glycosidic bond.
-D-glucose
-D-fructoseCopyright 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Learning Check
Write the structures and names of the two
monosaccharides that form when sucrose is
hydrolyzed.
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Sweeteners
Sugars and artificial
sweeteners
Differ insweetness.
Are compared tosucrose (tablesugar), which isassigned a value
of 100.
TABLE 15.2
60 000
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Learning Check
Identify the monosaccharides in each of the following:
A. lactose
(1) -D-glucose (2) -D-fructose (3) -D-galactose
B. maltose
(1) -D-glucose (2) -D-fructose (3) -D-galactose
C. sucrose
(1) -D-glucose (2) -D-fructose (3) -D-galactose
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Solution
Identify the monosaccharides in each of the following:
A. lactose
(1) -D-glucose (3) -D-galactose
B. maltose
(1) -D-glucose
C. sucrose(1) -D-glucose (2) -D-fructose
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14.6
Polysaccharides
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Polysaccharides
Polysaccharides
Are polymers of D-glucose.
Include amylose andamylopectin, starches made of
-D-glucose. Include glycogen (animal starch
in muscle), which is made of -D-glucose.
Include cellulose (plants andwood), which is made of
-D-glucose.
-D-glucose
O
CH2OH
OH OH
OH
OH
S f A l d
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Structures of Amylose and
Amylopectin
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Amylose
Amylose is
A polymer of -D-glucose molecules.
Linked by -1,4glycosidic bonds.
A continuous(unbranched)chain.
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Amylopectin
Amylopectin
Is a polymer of -D-glucose molecules.
Is a branched-chain
polysaccharide.
Has -1,4-glycosidicbonds between theglucose units.
Has -1,6 bonds tobranches.
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Glycogen
Glycogen
Is the polysaccharidethat stores -D-glucosein muscle.
Is similar toamylopectin, but ismore highly branched.
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Cellulose
Cellulose
Is a polysaccharideof glucose units inunbranched chains.
Has -1,4-glycosidicbonds.
Cannot be digestedby humans because
humans cannotbreak down -1,4-glycosidic bonds.
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Learning Check
Identify the polysaccharides and types of glycosidic
bonds in each of the following:
A. B. C.
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Solution
A. Cellulose -1,4-glycosidic bonds
B. Amylose -1,4-glycosidic bondsAmylopectin -1,4-and -1,6-glycosidic bonds
C. Glycogen -1,4-and -1,6-glycosidic bonds
(more branched than amylopectin)