Announcements & Agenda (04/11/07)
New Extra Credit Assignment Due Monday
Pick Up Old Graded Stuff
Pick Up Flowchart if you were absent Monday
Quiz Friday (13.4, 13.5, & Ch 14)
Exam Fri 04/20 (Ch 13,14,15)

Will Post Practice Exam Soon!
Today
 Finish Cyclic Monosaccharides
 Reactions of carbohydrates
 Disaccharides
 Polysaccaharides
1
What sugar is this?
0% 1.
Mannose
0% 2. Glucose
0% 3. Fructose
0% 4. Galactose
1
2
3
4
5
2
Is this the L- form or the D-form?
0% 1.
L
0% 2. D
0% 3. B
1
2
3
4
5
3
Which Structure is Correct?
0% 1.
A
0% 2. B
0% 3. C
0% 4. D
1
2
3
4
5
4
Last Time: Formation of Cyclic Glucose
Two “anomers” possible: a and b; this one is alpha
b/c the –OH is opposite the -CH2OH group!
5
Mutarotation: Interconversion of Anomers
• cyclic structures open and close.
• a-D-glucose converts to β-D-glucose & vice versa.
• at any time, only a small amount of open chain forms.
CH2OH
CH2OH
O
OH
H
O
OH
OH
OH
OH
a-D-glucose
(36%)
CH2OH
O
O
C
OH
H
OH
D-glucose (open)
(trace)
OH
OH
OH
OH
β-D-glucose
(64%) 6
Cyclic Structure of Fructose
• is a ketohexose.
• reacts the -OH on C-5 with the C=O on C-2
CH2OH
C O
CH2OH
HO C H
CH2OH
O
OH
H C OH
H C OH
CH2OH
O
OH
OH
OH
CH2OH
OH
OH
α-D-fructose
b-D-fructose
CH2OH
D-fructose
-OH from C5 attaches to C from C=O!
7
Chemical Properties of
Monosaccharides (14.4)
8
Reducing Sugars
• are monosaccharides that oxidize to give
a carboxylic acid.
• undergo reaction in the Benedict’s test.
• include the monosaccharides glucose,
galactose, and fructose.
• many disaccharides can also oxidize
•
but only if one monosaccharide can ring
open! (see later slides)
9
Oxidation of D-Glucose
O
O
C
H
C OH
H C OH
H C OH
[O]
HO C H
H C OH
+ Cu
2+
HO C H
H C OH
H C OH
H C OH
CH2OH
CH2OH
D-glucose
+ Cu2O(s)
D-gluconic acid
QUESTION: WHY CAN FRUCTOSE (A KETONE) BE OXIDIZED???
ANSWER: ISOMERIZATION TO AN ALDEHYDE…
10
One Test for Glucose in Urine:
Benedict’s Test
11
Reduction of Monosaccharides
• involves the
carbonyl group.
• produces sugar
alcohols, or
alditols.
• such as Dglucose gives
D-glucitol also
called sorbitol.
D-Glucitol
12
Learning Check
Write the products of the oxidation and
reduction of D-mannose.
O
C H
HO
H
HO
H
H
OH
H
OH
CH2OH
D-mannose
13
Solution
CH2OH
HO
H
HO
H
Reduction
O
O
C H
C OH
HO
H
HO
H
Oxidation
HO
H
HO
H
H
OH
H
OH
H
OH
H
OH
H
OH
H
OH
CH2OH
D-mannitol
CH2OH
CH2OH
D-mannose
D-mannonic acid
14
Disaccharides (14.5)
15
Important Disaccharides: Know These 3
A disaccharide consists of two monosaccharides.
Monosaccharides
Disaccharide
glucose + glucose
maltose + H2O
glucose + galactose
lactose + H2O
glucose + fructose
sucrose + H2O
16
Maltose
Free α-OH
A.K.A. “malt sugar”
obtained from starch
hydrolysis
used in cereals,
candies, and brewing
linked by an a-1,4glycosidic bond formed
from the a −OH on C1
of the 1st glucose and
−OH on C4 of the 2nd
glucose
found in both the aand β - forms
17
Lactose
• a disaccharide of
β-D-galactose
and α- or β-Dglucose.
• contains a β -1,4glycosidic bond.
• is found in milk
and milk products.
α-form
α-form
18
Sucrose
Sucrose or table sugar
• is obtained from sugar cane and sugar beets.
• consists of α-D-glucose and β-D-fructose.
• has an α,β-1,2-glycosidic bond.
α-D-glucose
β -D-fructose
Is a non-reducing sugar. Why?
19
Learning Check
Write the structures of the two
monosaccharides that form when sucrose
is hydrolyzed.
20
Solution
21
Polysaccharides
• often polymers of D-glucose.
• include amylose & amylopectin,
starches made of α-D-glucose.
• include glycogen (animal starch
in muscle), which is made of αD-glucose.
• include cellulose (plants and
wood), which is made of β-Dglucose.
CH2OH
O
OH
OH
OH
OH
α-D-Glucose
22
Starch: Structures of Amylose & Amylopectin
23
Amylose
• a polymer of α-Dglucose
molecules.
• linked by a-1,4
glycosidic bonds.
• a continuous
(unbranched)
chain.
24
Amylopectin
• also a polymer of
α-D-glucose
molecules.
• is a branched-chain
polysaccharide.
• has α-1,4glycosidic bonds
between the
glucose units.
• has α-1,6 bonds to
branches.
25
Glycogen
• is the
polysaccharide
that stores α-Dglucose in muscle.
• is similar to
amylopectin, but
is more highly
branched.
26
Cellulose
• a polysaccharide of
glucose units in
unbranched chains.
• has β-1,4-glycosidic
bonds.
• cannot be digested
by humans because
humans cannot
break down β-1,4glycosidic bonds.
27
Learning Check
Identify the polysaccharides and types
of glycosidic bonds in each of the
following.
A.
B.
C.
28
Solution
A. Cellulose
b-1,4-glycosidic bonds
B. Amylose
Amylopectin
a-1,4-glycosidic bonds
a-1,4-and a-1,6-glycosidic bonds
C. Glycogen
a-1,4-and a-1,6-glycosidic bonds
(more branched than amylopectin)
29
Other cool sugars…
Chitin (glucose w/ amide) = insect exoskeleton.
Similar to that in bacterial cell wall; makes bacterial cells
hard to break open. Lysozyme – defense protein to break
down cell walls
Cell surface, including ABO blood groups.
30
You are responsible for the Health
Note on Page 485!
31
More Interesting Info:
Sweetness of Sweeteners
• Sugars differ in
sweetness.
• are compared to
sucrose (table
sugar), which is
assigned a value
of 100.
60 000
32
History of Artificial Sweeteners
Saccharin: http://en.wikipedia.org/wiki/Saccharin
1879 Ira Remsen and Constantin Fahlberg at JHU
Monsanto Chemical Company in Saint Louis
became profitable in manufacturing and selling
saccharin.
Aspartame (Nutrasweet) was originally patented
by GD Searle in Chicago. 1985 Monsanto bought
GD Searle and created the NutraSweet Company.
Neotame (an analog of Aspartame) is 5 times
sweeter than Aspartame. See
http://www.neotame.com/
33
Chapter 15: Lipids… mmm…Fat…
15.1 Lipids
15.2 Fatty Acids
34