Announcements & Agenda (04/16/07)
Pick up Quizzes
Extra Credit Assignment Due NOW!
Exam Fri 04/20 (Ch 13,14,15)
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REVIEW @ 5 pm Wed!!!
exam will not include pp. 520-524
BTW, “Forms of Carbohydrates” tutorial on CD good for
looking at carbohydrate structures
Today
 Finish fatty acids (15.2)
 Triglycerides & reactions (15.3, 15.4)
 Glycerophospholipids (15.5)
 Cholesterol (15.6)
1
Last Time: 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
2
The monosacharides in glycogen in
are linked by…
0%1.
a-1, 4 glycosidic bonds only
b-1, 4 glycosidic bonds only
a-1, 6 glycosidic bonds only
Contain both a and b glycosidic bonds
None of the above
0%2.
0%3.
0%4.
0%5.
1
2
3
4
5
3
Last Time: Intro to Lipids (Fat!)
4
24 Good Practice Problems (Ch 15)
15.05, 15.11, 15.13, 15.19, 15.21,
15.27, 15.29, 15.31, 15.37, 15.39,
15.41, 15.43, 15.45, 15.49, 15.51,
15.57, 15.65, 15.67, 15.69, 15.71,
15.73, 15.77, 15.78, 15.81
Turn in your work for 15 of these by Wed @ 11 am
to receive 1 pt extra credit
5
Last Time: Lipids w/ 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
6
Last Time: Unsaturated vs.
Saturated Fatty Acids
• Unsaturated: contain one or
more cis double C=C bonds.
• have “kinks” in the fatty acid
chains.
•
•
•
•
do not pack as closely.
have fewer attractions between
chains.
have lower melting points.
are liquids at room temperature.
HOOC
H
H C
COOH
C
H
C
“kinks” in
chain
C
H
7
15.3
Waxes, Fats, and Oils
8
Waxes
• esters of saturated fatty acids and longchain alcohols.
• coatings that prevent loss of water by
leaves of plants.
9
Fats and Oils: Triacylglycerols
• also called triacylglycerols or
triglycerides
• esters of glycerol.
• produced by esterification.
• Formed when the hydroxyl
groups of glycerol react with
the carboxyl groups of fatty
acids.
10
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
11
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
12
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.
13
Oils w/ Unsaturated Fatty Acids
• have more unsaturated fats
• have cis double bonds that cause
“kinks” in the fatty acid chains
• “kinks” result in poor packing
• have lower melting points than
saturated fatty acids.
• are liquids at room temperature.
14
Diagram of Triacylglycerol with
Unsaturated Fatty Acids
Unsaturated fatty acid
chains with kinks cannot
pack closely.
15
Percent Saturated and Unsaturated Fatty
Acids In Fats and Oils
16
15.4 Chemical Properties of Triacylglycerols
The chemical reactions of triacylglycerols are
similar to those of alkenes and esters.
• Hydrogenation of double bonds in unsaturated
fatty acids by H2 (compare to alkenes).
• Hydrolysis of ester bonds by water in the
presence of an acid, a base, or an enzyme
(compare to esters).
17
Hydrogenation of Oils
• adds H2 to the
carbon atoms of
double bonds.
• increases the
melting point.
• produces solids
such as margarine
and shortening.
18
Hydrogenation
O
CH2
O
C
(CH2)5CH CH(CH2)7CH3
+ 3H2
O
CH
O
CH2
O
C (CH2)5CH CH(CH2)7CH3
CH2
O
C
O
O
C
(CH2)14CH3
O
(CH2)5CH CH(CH2)7CH3
glyceryl tripalmitoleate
(tripalmitolean)
Ni
CH
CH2
O
O
C (CH2)14CH3
O
C
(CH2)14CH3
glyceryl tripalmitate
(tripalmitin)
19
Olestra, A Fat Substitute
• used in foods as an artificial fat.
• sucrose linked by ester bonds to several
long-chain fatty chains.
• not broken down in the intestinal tract.
20
Olestra (WOW or Light)
http://en.wikipedia.org/wiki/Olestra
Launched in 1996 as WOW potato chips ($400
mil in 1998). Fell to $200 mil when FDA
restricted the label to state “may cause
abdominal cramping and loose stools”. It also
inhibited absorption of Vitamins A, D, E and K
It is made from one sucrose and 8 oleic acid
molecules. The molecule is so large that it could
not migrate past the intestinal wall
21
Cis and Trans Fatty Acids
Unsaturated fatty acids can be
• cis with bulky groups on same side of C=C.
CH3─ (CH2)5
(CH2)7─ COOH cis
C=C
H
H
• trans have bulky groups on opposite sides of C=C.
CH3─ (CH2)5
H
C=C
H
trans
(CH2)7─ COOH
22
Hydrogenation & Trans Fatty Acids
Most naturally occurring fatty acids have
cis double bonds!
• However, during hydrogenation, some cis double
bonds are converted to trans double bonds.
• In the body, trans fatty acids behave like saturated
fatty acids. Why?
• It is estimated that 2-4% of our total Calories is in
the form of trans fatty acid.
• Several studies reported that trans fatty acids raise
LDL-cholesterol and lower HDL-cholesterol.
23
Hydrolysis
• triacylglycerols split into glycerol and three fatty
acids.
• an acid or enzyme catalyst is required.
O
CH2
O
C
(CH2)14CH3
O
CH
CH2
O
O
C (CH2)14CH3 + H2O
O
C
(CH2)14CH3
H+
CH2
OH
CH
OH
CH2
OH
O
+
HO C
(CH2)14CH3
24
Saponification (Base Hydrolysis)
O
CH2 O C
(CH2)14CH3
O
CH O C
(CH2)14CH3
O
CH2 O C
+ 3NaOH
CH2 OH
(CH2)14CH3
CH OH
O
+ 3 Na+ -O C (CH2)14CH3
CH2 OH
“soap”
25
15.5 Glycerophospholipids
• the most abundant lipids in cell membranes.
• composed of glycerol, two fatty acids,
phosphate, and an amino alcohol.
Fatty acid
Glycerol
Fatty acid
PO4
Amino
alcohol
26
Polarity of Glycerophospholipids
A glycerophospholipid has
• 2 nonpolar fatty acid chains.
• A phosphate group and a polar amino alcohol.
CH3
│+
+
HO−CH2−CH2−N−CH3
HO−CH2−CH2−NH3
│
choline
CH3
ethanolamine
+
NH3
│
HO−CH2−CH−COO−
serine
Amino alcohols
27
Structure and Polarity of A
Glycerophospholipid
28
Lecithin & Cephalin
Lecithin and cephalin are glycerophospholipids
• abundant in brain and nerve tissues.
• found in egg yolk, wheat germ, and yeast.
29
15.6 Steroids: Cholesterol, &
Steroid Hormones
CH3
CH3
CH3
CH3
CH3
HO
30
Steroid Nucleus
Consists of:
• 3 cyclohexane rings.
• 1 cyclopentane ring.
• no fatty acids.
steroid nucleus
31
Cholesterol
• is the most abundant steroid in the body.
• has methyl CH3- groups, alkyl chain, and OH attached to the steroid nucleus.
CH3
CH3
CH3
CH3
CH3
HO
32
Cholesterol in the Body
• is obtained from meats,
milk, and eggs.
• is synthesized in the liver.
• is needed for cell
membranes, brain and
nerve tissue, steroid
hormones, and Vitamin D.
• clogs arteries when high
levels form plaque.
A normal, open artery.
An artery clogged
by cholesterol
plaque
33
Cholesterol in Foods
• is considered
elevated if
plasma
cholesterol
exceeds 200
mg/dL.
• is synthesized
in the liver and
obtained from
foods.
34
Lipoproteins: LDL, HDL, Etc…
• combine lipids
with proteins &
phospholipids.
• are soluble in
water because
the surface
consists of polar
lipids.
35
Types of Lipoproteins
• differ in density, composition, and function.
• include low-density lipoprotein (LDLs) and
high-density lipoprotein (HDLs).
36
Transport of Lipoproteins in the Body
37