Lipids.1
Practice Problems on Lipids
1.
Which one of the following compounds has the structural pattern of the naturally
occurring fats or oils?
a)
COO
CHO
COO
O
CH2 O C
O
b)
CH2 O C
O
CH2O
O
CH O C
O
CH2 O C
c)
COOH
COOH
COOH
O
d)
CH2O
CH O
CH2 O
O
O
C
CH2 O
e)
CH
O
CH2 O
2.
Which of the following compounds is least likely to be a natural fatty acid?
O
a)
OH
O
b)
OH
O
c)
OH
O
d)
OH
O
OH
e)
Lipids.2
3.
Which of the following compounds is most likely to be a solid?
O
A
C
O
O
C
O
O
C
O O
B
C
O
O
C
O
O
C
O
O
C
C
O
O
C
O
O
C
O
O
C
O
O
D
C
O
O
C
O
O
C
O
O
E
C
O
O
C
O
Lipids.3
4.
Which of the following fatty acids is least likely to be found in a natural fat or oil?
O
A
C
OH
O
C
B
OH
O
C
C
OH
O
C
D
OH
O
E
5.
C
OH
Which of the following is most likely a natural fatty acid?
A
COOH
B
COOH
C
COOH
D
E
HOOC
COOH
COOH
Lipids.4
6.
Which of the following mechanistic steps are not part of the mechanism for the
Claisen condensation of methyl acetate (CH3COOCH3 in CH3ONa/methanol)?
O
O
I
C
CH2
CH2
OCH 3
C
OCH 3 + CH3 OH
H
OCH 3
II
CH3
C
OCH 3
CH2
C
O
O
O
O
CH3
OCH 3
C CH2 C OCH 3
+ CH3 O
O
O
III
CH3
C
CH2
CH3
OCH 3
C
O
C CH2 C OCH 3 + CH3 O
OCH 3
O
IV
CH3
C
O
O
O
OCH 3
CH2
C
OCH 3
CH3
C
CH2
OCH 3
C
O
A) II
B) III and IV
C) II and III
D) I and IV
E) I and II
OCH 3
Lipids.5
7.
Which one of the following is the normal product of the reaction sequence
catalyzed by the fatty acid synthetase complex?
O
a)
S ACP
O
b)
S ACP
O
c)
S ACP
O
d)
S ACP
e)
O
O
O
O
O
O
O
O
S ACP
8.
Which one of the following compounds would not be an intermediate in the
biochemical synthesis of the compound below?
O
C
A
B
O
O
O
O
C
C
C
C
O
O
C
C
OH
SACP
SACP
OH
O
C
C
SACP
O
C
D
E
O
O
O
C
C
SACP
SACP
Lipids.6
9.
Which one of the following is least likely to be involved in the biosynthesis of
palmitic acid?
OH
O
O
O
O
SFAS
SACP
A
O
SACP
B
C
O
O
O
SACP
SACP
D
10.
E
Which one of the following processes is most likely to be involved in the
mechanism of fatty acid synthase? In all cases "HA" or "B" are part of an enzyme
active site, and "R" is the rest of NADPH
A
A
H
A
H3C
CH
CH
C
H
O
O
OH
SACP
H
B
H3C C C C SACP
H
C
H
CONH2
R
R
A
D
H3C
H
N
OH
CH
C
H
CH
N
R
E
SACP
H
CONH2
H
O
O
H
CONH2
C
C
SACP
B
N
O
C
H
B
H
H3C
OH O
H3C
C
H
CH2
A
C
SACP
Lipids.7
11.
Which one of the A – E correctly shows the mechanism of a Michael Addition?
O
A)
HO
H
Nu
C
B)
H
CH2OH
O
O
C)
D)
N
N
Nu
O
E)
H OH
12.
When NADPH acts as a reducing agent, which H is transferred to the compound
being reduced? (Circle correct H)
H H
H
O
C
NH2
H
OH
HO P O CH2
N
O
H
H
H
H
OH
O
H
OH
NH2
N
N
HO P O CH2
O
H
O
H
H
H
OH
OH
N
N
Lipids.8
13.
In fatty-acid biosynthesis, acetyl CoA is converted into malonyl CoA. Why is
malonyl CoA synthesized?
A) To incorporate another carbon from CO2 into the growing chain
B) To provide a catalytic group able to act as a base
C) To make the Claisen step favour product formation
D) To make malonyl CoA more soluble in water
E) To make malonyl CoA bind more strongly to fatty acid synthetase
14.
To convert acetyl-CoA into CH3-(CH2)14-CO-S-R, how many equivalents of
NADPH must the cell use per equivalent of product formed? (Work out answer)
15.
In nature, biotin is used as a:
A) Reducing agent
B) Dehydrating agent
C) Carbonyl transfer agent
D) Oxidizing agent
E) Hydrating agent
Lipids.9
16.
Palmitic acid with the carbon atoms numbered is shown below. Which C-C bond
is formed by the Claisen condensation between butyryl thiolester (a 4 carbon
electrophile) and malonyl-ACP?
16 15 14 13 12 11 10 9 8 7
6 5 4 3 2 1
O
OH
A) C14 – C15
B) C8 – C9
C) C10 – C11
D) C12 – C13
E) C4 – C5
17.
Butanoic acid is biosynthesized by a route identical to the fatty acid biosynthetic
pathway. If, during the biosynthesis of butanoic acid, all of the starting material
(acetyl CoA) is isotope labelled at the methyl carbon atom as indicated by the
asterisk, which atom(s) will be labelled in the product? Assume that the only
organic carbon source is acetyl CoA.
O
O
H3C*
SCoA
H3C
I II III IV
A) I and III only
B) I and II only
C) II and IV only
D) II and III only
E) I only
OH
Lipids.10
18.
Which one of the following compounds will most likely form micelles in water?
OH
OH
A
HO
HO
HO
O
O
O
OH
HO
HO
B
COO Na
C
D
E
SO3Na
19.
SO3Na
Which one of the following would not act as a soap or detergent?
A
N(CH3)3 Cl
B
OSO3 Na
C
OH
D
O
E
COO
O
Na
O
O
O
OH
Lipids.11
20.
Early settlers in Canada prepared soap by boiling animal fat with wood ashes, a
source of NaOH and KOH. This technique can be seen at the Lower Fort Garry
National Historic Site in Manitoba. Which one of the following statements about
this soap-making process is NOT correct?
A) This process is called saponification
B) After the hydrolysis the soap is precipitated by NaCl
C) Soap made this way give precipitates with hard water
D) Soaps made this way contain phosphates that bind metal ions
E) Soaps made this way are readily biodegradable
21.
How many of the following are soluble in water?
CH3(CH2)22CO2H
CH3(CH2)16CO2K
[CH3(CH2)4CH=CH(CH2)7CO2]2Ca
H2C OCO(CH2)14CH3
[CH3(CH2)12CH2SO3]2Mg
HC OCO(CH2)14CH3
H2C OCO(CH2)14CH3
22.
Which one of the following is not an effective cleaning agent?
O
2+
A
O
B
SO3
2
Mg
2+
2
O
O
C
D
K
O
O
Na
SO3 Na
E
Ca
Lipids.12
23.
Which one of the following detergents would not be a good laundry product when
used with hard water?
A
OSO3 Na
B
SO3 Na
CO 2
C
Na
D
SO3 Na
E
24.
OSO 3 Na
O
Which one of the following is not likely to be a useful part of a detergent
formulation?
a)
O
O
O
d)
b)
O
P
O
O
Si
COO
O
COO
e)
COO
CH2 COO
N
H2C
NH
CH
NH
NH2
NH
CH
NH
H2N
NH2
CH2
OOC
NH2 H2N
H2N
CH2
CH2
N CH2CH2 N
CH2
CH2
COO
c)
O
O Si
Si OH
O
HO
O
P
P O
O
O
O
COO
HO
H2N
NH2
Lipids.13
25.
During the synthesis of an alkylbenzenesulfonate detergent, the following
transformation below is made. Which of 1-5 are involved in the correct
mechanism?
H
+
1
H
H
2
H
H
H
3
H
H
H
H
4
+
H
H
5
H
A) Only 2 and 3
B) Only 1 and 4
C) Only 2, 3, and 5
D) Only 1, 4, and 5
E) All of the steps are involved
H
+
H
Lipids.14
26.
Which chemical step is least likely to occur?
H
SO3H
SO3H
A)
SO3H
H
SO3H
B)
NO2
NO2
H
SO3H
SO3H
C)
OCH3
OCH3
SO3H
H
SO3H
D)
H
H
SO3H
H
SO3H
E)
NH
NH
O
O
Lipids.15
27.
The following polymer can be synthesized by the acid-catalyzed polymerization
of which building block?
*
28.
*
A)
B)
D)
E)
C)
Which one of the following is not biodegradable?
A
SO3 Na
B
SO3 Na
N(CH3)3 Cl
C
D
E
HO
O
O
OH
COO Na
CH2OH
OH
Lipids.16
29.
Which one of the following statements best describes why phospholipids form
bilayers whereas the metal salts of fatty acids form micelles in aqueous solution
A) The aggregates formed in aqueous solution reflect a balance between
maximizing the electrostatic attraction of the head groups and minimizing the
contact of the lipophilic tail groups
B) The repulsion between water and the tail groups of the metal salts of fatty
acids is minimized in a micellular structure
C) The aggregates formed in aqueous solution reflect a balance between
maximizing hydrogen bonding between the head groups and maximizing the
contact between the lipophilic tail groups.
D) The aggregates formed in aqueous solution reflect a balance between
minimizing the electrostatic replusion of the head groups and maximizing the
contact of the lipophilic tail groups
E) The electrostatic repulsion between the ionic head groups of metal salts of
fatty acids is maximized in a micellular structure
30.
PGF (shown below) is an extremely important prostaglandin that stimulates the
contraction of smooth muscles. Which of the oxygen atoms in PGF
from the cyclooxygenase-catalyzed reaction using oxygen molecules from the
air?
a
HO
e
O
d
HO
b
A) a and b only
B) a, b, and c only
C) e and d only
D) a and c only
E) all except for e
OH
c
OH
Lipids.17
31.
Which one of the following statements about prostaglandins is incorrect?
A) Accolate and Singular interfere with the action of prostaglandins.
B) Vioxx, Celebrex, and Bextra all inhibit the oxidation of arachidonic acid.
C) Many prostaglandins are inflammatory agents.
D) The enzymatic oxidation of arachidonic acid forms a 5-membered ring.
E) Prostaglandins are synthesized primarily in the prostate gland.
32.
Which one of the lipids would not be found as part of a biological membrane?
O
C
O
A
C
O
O
CH2
CH2 O P O CH2 C NH3
O
C
O
NH
CH2 O P O CH2 CH2 N(CH3)3
OH
C
O
C
NH
OH
CH2 O
Cl
O
HO
O
OH
CH2OH
O
D
E
COO
O
OH
B
H
O
CH
C
O
C
O
O
NH
O
CH2 O P O CH2 CH2 N(CH3)3
O
Cl
Lipids.18
33.
Which one of the following will form a bilayer by itself?
O
O
A
O
B
O
C
O O
C
O O
C
CH3
O
O
O
O
O
P
N(CH3)3
O
O
O
C
C
O
O
C
O O
D
C
O
O
O
O
P
O
N(CH3)3
E
OH
34.
Which one of the following statements is not correct?
A) The first step of prostaglandin synthesis from arachidonic acid involves the
formation of a cyclopentane ring by the enzyme cyclooxygenase.
B) Phospholipid bilayers are leaky and compounds can easily pass unassisted
through the bilayer.
C) In electrophilic aromatic substitution, electron-donating substituents on the
aromatic ring are ortho/para directors.
D) Phosphate compounds can be added to detergents to increase their
performance in hard water.
E) Micelles have a hydrophobic interior.
Lipids.19
35.
Which one of the following is not a terpene?
B
A
C
O
E
D
OH
36.
Which one of the following is not a terpene?
b) COOH
a)
COOH
OH
c)
O
O
O
e)
d)
O
O
Lipids.20
37.
Which one of the following is not a terpene?
B
A
C
O
OH
E
D
O
O
38.
The enzyme catalyzed reaction between dimethylallyl pyrophosphate and
isopentenyl pyrophosphate to give geranyl pyrophosphate is shown below.
Which of the following arrows indicate where there is a significant build up of
positive charge during the reaction?
V
3
3
OP2O6
OP2O6
OP2 O6
IV
III
I
II
dimethylallyl pyrophosphate
A) At carbons I, III, and V
B) At carbons I, II, and V
C) At carbons II and IV
D) At carbons I, II, and V
E) At carbons III and IV
isopentenyl pyrophosphate
geranyl pyrophosphate
3
Lipids.21
39.
Which compound is a terpene, based on obeying the isoprene rules?
O
O
O
OH
A)
B)
OH
bulnesol
isohumulone - bitter tasting
and found in beer
OH
C)
D)
O
iso-germacrene D
OH
HO
(CH2)4CH3
tetrahydrocannabinol found in plants
O
O
E)
humulone - from hops
and found in beer
Lipids.22
40.
Terpenes are biosynthesized from dimethylallyl pyrophosphate and isopentenyl
pyrophosphate. Describe, in words, and by writing a mechanism, how these two
molecules are linked together to form geranyl pyrophosphate.
OPP
Dimethylallyl
pyrophosphate
41.
Geranyl
pyrophosphate
OPP
Isopentenyl
pyrophosphate
Which one of the following carbon-carbon linkages was most likely to have been
formed by a reductive dimerization reaction?
A
B
C
D
O
E
42.
The reaction step shown occurs during the biosynthesis of terpenes and steroids.
Which one of statements A – E is correct?
H3C OH
H3C OH
Enzyme
COSR
COSR
H2O
COOH COSR
A) The two thioester groups in the starting material differ in chemical reactivity.
B) Production of a single enantiomer from an achiral starting material requires a
chiral catalyst.
C) The product retains a plane of symmetry.
D) This reaction requires NADPH.
E) The carbonyl carbon of the remaining thiolester will subsequently be reduced
and removed.
Lipids.23
43.
Which one of the following molecules is involved in terpene biosynthesis?
OPO2OPO3
A
OPO2OPO3
B
OPO2OPO3
C
OPO2OPO3
D
E
OPO2OPO3
44.
Calculate the number of moles of ATP needed to synthesize one mole of
dimethylallyl pyrophosphate from three moles of acetyl CoA.
Lipids.24
45.
The tail of chlorophyll is comprised of a terpene alcohol,
phytol. Phytol can be biosynthesized exclusively from acetyl
CoA tagged with carbon-13 isotope as the carboxyl carbon
atom and carbon-14 isotope as the methyl carbon atom, as
shown on the right.
O
C
H3C 13
14
SCoA
Which one of A – E shows phytol with the correct placement of atoms?
13
A.
OH
14
14
B.
14
14
13
OH
14
14
14
13
C.
14
13
14
14
13
14
13
13
14
13
13
14
14
13
14
14
13
14
14
13
14
13
13
OH
13
13
13
13
14
OH
14
14 14
13
13
13
13
13
13
14
14
13
13
13
14
14
14
13
E.
13
13
14
D.
14
13
13
46.
14
14
13
14
14
13
OH
The red colour of tomatoes is attributed to the antioxidant lycopene, the
consumption of which has been suggested to reduce the risk of certain cancers.
How many head-to-tail linkages of the isoprene building block are present in
lycopene, a C40 tetraterpene?
A) 5
B) 3
C) 4
D) 7
E) 6
Lipids.25
47.
During the synthesis of mevalonic acid, the reaction below takes place. Which
one of statements A – E is not correct?
O
CH3 C
CH2
C SR
+
CH3
O
OH
O
O
CH3 C
C SR
CH2
C SR
O
CH2
C SR
A) This aldol reaction is the result of a nucleophilic attack by the enolate of the
acetylthiolester on a -ketothiolester.
B) The enolate of the acetylthiolester attacks the keto carbonyl rather than the
thiolester carbonyl because the thiolester carbonyl is less electrophilic.
C) This enzyme-catalyzed reaction results in the formation of only one
enantiomer.
D) It is not necessary to generate the enolate of the acetylthiolester by a
decarboxylation since the thermodynamics of the aldol reaction are
favourable.
E) The -ketothiolester (the starting material) was formed in a modified Claisen
condensation between an acetyl thiolester and a malonyl thiolester.
48.
Which one of the following is not a steroid?
OH
O
HO2C
HO
b
a
OH
O
HO
c
d
e all are steroids
Lipids.26
49.
Which one of the following represents the folding of squalene oxide that is used
for the enzyme-catalyzed cyclization to lanosterol?
A
C
O
O
O
D
O
E
50.
B
O
Cholesterol is biosynthesized from the triterpene
squalene, which has a single tail-to-tail (T-T)
connection. Which bond in cholesterol
corresponds to that T-T bond originally present
in squalene?
D
B
E
A
C
HO
51.
Which one of the following compounds is least likely to be involved in the
biosynthesis of cholesterol?
A
OP2O6H2-
C
O P2O6H2-
E
B
O P2O6H2-
D
O P2O6H2-
O P2O6H2-
Lipids.27
52.
Squalene epoxide is converted to lanosterol by two major processes. The first
process is the carbon-carbon bond-forming reactions which form the
characteristic steroid ring structure. The second process involves group and
atom migrations and the elimination of a proton ultimately giving lanosterol. With
respect to the first process only (the cyclization reactions), which atoms would
bear some positive charge (even temporarily)?
7
8
10 9
4
H O
2
1
A) 1, 2, 3, 4, 5
B) 1, 9, 3, 4, 6
C) 1, 2, 3, 7
D) 10, 9, 2, 3, 8, 4
E) 10, 2, 8, 7
3
5
6
Lipids.28
53.
During the biosynthesis of cholesterol, squalene oxide is converted to lanosterol
as shown below. Notice that one of the methyl groups in squalene oxide has
been labeled with a star. Which one of the following methyl groups in lanosterol
originated as the labeled methyl group in squalene oxide?
HO
O
squalene oxide
lanosterol
E
D
B
C
HO
A
54.
Which one of the following statements about vitamin E is not correct?
HO
O
A) Vitamin E can form a resonance stabilized radical.
B) Vitamin E can form a hindered radical.
C) Vitamin E is a fat-soluble vitamin.
D) Molecules with similar structural features as vitamin E are used as
antioxidants (preservatives) in foodstuffs.
E) Vitamin E is a triterpene.
Lipids.29
55.
Which one of the following statements is NOT correct?
A) Vitamin C is a fat-soluble vitamin.
B) Vitamin K is required for the coagulation of blood.
C) Polar bears store large amounts of Vitamin A in their liver.
D) Vitamin D is a cholesterol derivative.
E) The biosynthesis of vitamin D requires light.
56.
Which one of the following compounds would not be classified as a lipid?
OH
HO
COOH
HO
OH
O
B
A
HO
HO
(CH3)3NCH2CH2OPO3
C
H3C
O2C
CH3
CH3
O2C
CH3
O2C
D
CH3
CH2OH
E
Lipids.30
57.
Which one of the following steps is consistent with a nucleophilic acyl substitution
mechanism?
O
O
NH
NH
A)
O
S
O
O
O
H
H
O
O S
OH
O
O
O
SCoA
O
B)
SCoA
SCoA
O
SCoA
O
O
C)
SCoA
SCoA
O
SCoA
SCoA
Cl
D)
Cl
N
N
N
O
N
Cl
N
N
NH2-R
H2N-R
Cl
Cl
O
O
N C CH
CH
E)
Cl
C
H
OH
H
OH
N
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
Lipids.31
58.
The sequence of events listed below corresponds to which reaction mechanism?
1. Protonation of sp2 oxygen
2. Nucleophilic attack and formation of tetrahedral intermediate
3. Proton transfer
4. Collapse of tetrahedral intermediate, regeneration of
sp2 oxygen, and loss of leaving group
5. Deprotonation
A) Electrophilic aromatic substitution
B) Acid-catalyzed nucleophilic addition
C) Saponification
D) SN1 substitution
E) Acid-catalyzed nucleophilic acyl substitution
59.
When detergents are dissolved in water, the pH of the resulting solution is close
to neutral, while soap solutions are alkaline. Which statement best explains this
phenomenon?
A) Detergents contain less unsaturation than soaps.
B) Detergents are typically salts of strong acids.
C) Soaps precipitate in the presence of Ca2+.
D) Soaps are carboxylic acids, which are soluble in bases.
E) Detergents are made from natural oils and fats, which are not basic.
60.
A dichloromethane solution containing 5% bromine by volume can be prepared
by combining which one of the following?
A) 95 mL of dichloromethane and 5 mL of bromine
B) 95 g of water and 5 g of bromine that is dissolved in dichloromethane
C) 95 mL of water and 5 mL of bromine dissolved in dichloromethane
D) 95 g of dichloromethane and 5 g of bromine
E) 95 mL of bromine and 5 mL of dichloromethane
Lipids.32
61.
Which one of the following shows the product(s)
of the reaction of the glyceride (shown at right)
with excess bromine? (No stereochemistry is
implied by the structures)
O
CH2 O C
O
(CH 2) 7CH CH(CH 2)8CH 3
CHO
(CH 2) 7CH CH(CH 2)8CH 3
C
O
CH2 O C
A
O
CH2O
Br
C
O
CHO
(CH2)7CH CH(CH2)8CH3
Br H
(CH2)7CH
C
CH2O
(CH2)7CH
C
Br
O
O
C
Br
C
CHO
(CH2)7CH
C
CH2O
(CH2)7CH
C
H
(CH2)7CH
Br
O
Br
Br
C
(CH2)7CH
HO
D
C
HO
CH2OH
CH(CH2)8CH3
CHOH
HO
(CH2)7CH
C
O
O
E
C
HO
Br
Br
(CH2)7CH
CHBr
+
O
Br
C
(CH2)7CH
HO
CH(CH2)8CH3
Br
Br
CH(CH2)8CH3
Br
CH(CH2)8CH3
+
CH2Br
HO
C
O
(CH2)7CH
Br
Br
(CH2)7CH
CH(CH2)8CH3
+
+
C
HO
(CH2)7CH
CH(CH2)8CH3
+
+
CH2Br
CH(CH2)8CH3
O
+
CH2OH
CH(CH2)8CH3
O
CH(CH2)8CH3
Br
Br
(CH2)7CH CH(CH2)8CH3
Br Br
O
CH(CH2)8CH3
+
+
CH2O
CH(CH2)8CH3
Br
HO
CH2OH
O
O
C
CHOH
B
H
(CH 2) 7CH CH(CH 2)8CH 3
CH(CH2)8CH3
Br
CH2OH
HO
C
O
(CH2)7CH
CH(CH2)8CH3