Announcements & Agenda (04/13/07)
Extra Credit Assignment Due Monday
Quiz Today
Exam Fri 04/20 (Ch 13,14,15)
Today
 Polysaccaharides
 Lipids (15.1-15.3)
1
Last Time: Oxidation & Reduction
of Mono (and Di) Saccharides
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
2
Last Time: Disaccharides to Know
• A disaccharide consists of two monosaccharides.
Monosaccharides
Disaccharide
glucose + glucose
maltose + H2O
glucose + galactose
lactose + H2O
glucose + fructose
sucrose + H2O
• Factors that distinguish one disaccharide from another
•
Identity of monosaccharides
•
Type of glycosidic bond (e.g. maltose: a-1, 4 glycosidic
bond)
•
Can still have a/b forms
3
Example: Sucrose
• 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?
http://en.wikipedia.org/wiki/Image:Glucose_Conversion.gif
4
Learning Check
Write the structures of the two monosaccharides
that form when sucrose is hydrolyzed.
5
Solution
6
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
7
Starch: Structures of Amylose & Amylopectin
8
Amylose
• a polymer of α-Dglucose
molecules.
• linked by a-1,4
glycosidic bonds.
• a continuous
(unbranched)
chain.
9
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.
10
Glycogen
• is the
polysaccharide
that stores α-Dglucose in muscle.
• is similar to
amylopectin, but
is more highly
branched.
11
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 the β1,4-glycosidic bonds
of cellulose.
12
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.
13
You are responsible for the Health
Note on Page 485!
14
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
15
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/
16
Chapter 15: Lipids… mmm…Fat…
15.1 Lipids
15.2 Fatty Acids
17
Lipids
Building blocks
• biomolecules that contain fatty acids or a steroid
nucleus.
• soluble in organic solvents, but not in water.
• named for the Greek word lipos, which means
“fat.”
• extracted from cells using organic solvents.
18
Types of Lipids: 2 Broad Classes
19
Fatty Acids
• long-chain carboxylic
acids.
• typically 12-18 carbon
atoms.
• insoluble in water.
• saturated or
unsaturated.
Olive oil contains 84%
unsaturated fatty acids and 16%
saturated fatty acids
20
Saturated & Unsaturated Fatty Acids
• saturated: all
single C–C
bonds.
• unsaturated:
with one or
more double
C=C bonds.
O
C OH
palmitic acid, a saturated acid
O
C OH
palmitoleic acid, an unsaturated acid
21
Properties of Saturated Fatty Acids
• contain only single C–C bonds.
• are closely packed.
• have strong attractions between chains.
• have high melting points.
• are solids at room temperature.
COOH
COOH
COOH
22
Properties of Unsaturated Fatty Acids
• contain one or more cis
double C=C bonds.
• have “kinks” in the fatty
acid chains.
•
•
•
•
do not pack closely.
have few attractions between
chains.
have low melting points.
are liquids at room
temperature.
HOOC
H
H C
COOH
C
H
C
“kinks” in
chain
C
H
23
Learning Check
Assign the melting points of –17°C, 13°C, and 69°C
to the correct fatty acid. Explain.
stearic acid
oleic acid
linoleic acid
(18 C)
(18 C)
(18 C)
saturated
one double bond
two double bonds
24
Solution
Stearic acid is saturated and would have a higher
melting point than the unsaturated fatty acids.
Because linoleic has two double bonds, it would have
a lower mp than oleic acid, which has one double
bond.
stearic acid mp 69°C
saturated
oleic acid
mp 13°C
linoleic acid mp -17°C
most unsaturated
25
15.3
Waxes, Fats, and Oils
26
Waxes
• esters of saturated fatty acids and longchain alcohols.
• coatings that prevent loss of water by
leaves of plants.
27
Fats and Oils: Triacylglycerols
•
•
•
•
also called triacylglycerols.
esters of glycerol.
produced by esterification.
Formed when the hydroxyl
groups of glycerol react with
the carboxyl groups of fatty
acids.
28
Triacylglycerols
In a triacylglycerol, glycerol forms ester
bonds with three fatty acids.
REMEMBER ACID CATALYZED ESTERIFICATION!
…OR FROM LAB!
29
Formation of a Triacylglycerol
glycerol
+
three fatty acids
triacylglycerol
O
CH2
OH
CH
OH
CH2
OH
+
HO C
O
(CH2)14CH3
HO C
O
(CH2)14CH3
HO C
(CH2)14CH3
O
CH2 O C
(CH2)14CH3
O
CH O C
(CH2)14CH3 + 3H2O
O
CH2 O C
(CH2)14CH3
30
Different Fatty Acids Can Make
Up Triacylglycerols!
O
CH2
O
C
(CH2)16CH3
Stearic acid
O
CH
O
CH2
O
C (CH2)7CH CH(CH2)7CH3
O
C
(CH2)12CH3
Oleic acid
Myristic acid
31
Melting Points of Fats and Oils
A fat
• is solid at room temperature.
• is prevalent in meats, whole milk, butter,
and cheese. (mmm… cheese)
An oil
• is liquid at room temperature.
• is prevalent in plants such as olive and
safflower.
32
Oils w/ Unsaturated Fatty Acids
• have more unsaturated fats.
• have cis double bonds that cause
“kinks” in the fatty acid chains.
• with “kinks” in the chains do not allow
the triacylglycerol molecules to pack
closely.
• have lower melting points than
saturated fatty acids.
• are liquids at room temperature.
33
Diagram of Triacylglycerol with
Unsaturated Fatty Acids
Unsaturated fatty acid
chains with kinks cannot
pack closely.
34
Percent Saturated and Unsaturated Fatty
Acids In Fats and Oils
35