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Chapter 20: Lipid Metabolism
Exam Autumn 2017, questions and answers
Biochemistry I (Southeastern Louisiana University)
Matching
Answers available at http://bit.ly/3cTLh4q
Choose the correct answer from the list. Not all the answers will be used.
A)
B)
C)
D)
E)
F)
G)
H)
I)
J)
K)
L)
HDL
propionyl-CoA
LDL
Dihydroxyacetone phosphate
malonyl-CoA
ACP
chylomicrons
phosphopantetheine
flavin
albumin
ketone bodies
cholesterol
1. Lipoproteins formed in the intestinal mucosal cells are called
Section: 20.1.B
Level of Difficulty: Easy
Learning Objective: Lipid Digestion, Absorption, and Transport
Answers available at http://bit.ly/3cTLh4q
2. Cholesterol and other lipids are transported from tissues to the liver by
Section: 20.1.B
Level of Difficulty: Easy
Learning Objective: Lipid Digestion, Absorption, and Transport
3. The glycerol backbone of triacylglycerols is catabolized to
.
Section: 20.1.B
Level of Difficulty: Easy
Learning Objective: Lipid Digestion, Absorption, and Transport
Answers available at http://bit.ly/3cTLh4q
4. Free fatty acids bind to
Section: 20.2
Level of Difficulty: Easy
for circulation in the bloodstream.
.
.
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Learning Objective: Fatty Acid Oxidation
5. Cells take up
Section: 20.1.B
by receptor mediated endocytosis.
Level of Difficulty: Easy
Learning Objective: Fatty Acid Oxidation
Answers available at http://bit.ly/3cTLh4q
6. The oxidation of odd-numbered fatty acids results in
Section: 20.2.E
Level of Difficulty: Easy
Learning Objective: Fatty Acid Oxidation
as a final product.
7. The molecules acetoacetate, acetone, and D- -hydroxybutyrate are metabolic fuels termed
Section: 20.3
Level of Difficulty: Easy
Learning Objective: Ketone Bodies
8. Acyl carrier protein (ACP) contains a
Section: 20.4.C
Level of Difficulty: Easy
Learning Objective: Fatty Acid Biosynthesis
.
prosthetic group.
Answers available at http://bit.ly/3cTLh4q
9. Fatty acid synthesis requires both acetyl-CoA and
Section: 20.4.B
Level of Difficulty: Easy
Learning Objective: Fatty Acid Biosynthesis
10.
as initiator molecules.
is formed from ordered sequence of condensation of isoprene units.
Section: 20.7.A
Level of Difficulty: Easy
Learning Objective: Cholesterol Metabolism
Answers available at http://bit.ly/3cTLh4q
Multiple Choice
11. Digestion of triacylglycerols is aided by the cholesterol derivatives synthesized by the liver known as
A)
bile acids.
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B)
lipoproteins.
C)
lanosterols.
D)
chylomicrons.
E)
colipases.
Section: 20.1.A
Level of Difficulty: Moderate
Learning Objective: Lipid Digestion, Absorption, and Transport
12. Which of the following would result in a net increase in uptake of LDL by the liver?
A)
increased availability of LDL receptors
B)
high levels of cholesterol synthesis
C)
increased availability of clathrin triskelions
D)
all of the above
E)
none of the above
Section: 20.1.B
Level of Difficulty: Difficult
Learning Objective: Lipid Digestion, Absorption, and Transport
13. Which of the following is required for entry of fatty acids into the oxidation pathway?
I. priming via the enzyme acyl CoA synthetase
II. conservation of free energy from ATP hydrolysis by use of a thioester linkage
III. transport to the cytosol for oxidation via a carnitine carrier protein
IV. hydrolysis of carnitine palmitoyl transfer protein
A)
I, II
B)
I, II, III
C)
I, II, III, IV
D)
III, IV
E)
I, III
Section: 20.2.A
Answers available at http://bit.ly/3cTLh4q
Level of Difficulty: Difficult
Learning Objective: Fatty Acid Oxidation
14. Which of the following vitamins is part of the prosthetic group 5 -deoxyadenosylcobalamin?
A)
B)
C)
D)
B1
B2
B6
B12
E)
none of the above
Section: 20.2.E
Level of Difficulty: Easy
Learning Objective: Fatty Acid Oxidation
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15. , a condition in which acetoacetate production exceeds it metabolism and results in a sweet breath
odor due to nonenyzmatic
of acetoacetate to
.
A)
B)
C)
D)
E)
ketosis; decarboxylation; hydroxylbutryate
ketosis; carboxylation; hydroxylbutryate
ketosis; carboxylation; acetone
glyceroneogenesis; decarboxylation; hydroxylbutryate
glyceroneogenesis; decarboxylation; acetone
Section:
20.3
Level of Difficulty: Moderate
Learning Objective: Ketone Bodies
Answers available at http://bit.ly/3cTLh4q
16. Triacylglycerols are synthesized by
A)
B)
C)
D)
E)
during times of starvation via a process known as
.
Dihydroxyacetone phosphate; ketosis
Dihydroxyacetone phosphate; glyceroneogenesis
acetyl CoA; ketosis
acetyl CoA; glyceroneogenesis
ketone bodies; ketosis
Section:
20.4.E
Level of Difficulty: Moderate
Learning Objective: Fatty Acid Biosynthesis
17. Two phosphatidylglycerol molecules condense to form the molecule
eliminated as the side product.
A)
B)
C)
D)
E)
, and glycerol is
phosphatidic acid
cardiolipin
plasmalogen
sphingomyelin
squalene
Section:
20.6.B
Level of Difficulty: Easy
Learning Objective: Synthesis of Other Lipids
18. The activity of lipases is controlled in part by a process known as
due to the
where lipases are active.
A)
B)
which functions effectively
interfacial activation; lipid-water interface
lipase activation; lipid-water interface
C)
lipase activation; bile salt-water interface
Answers available at http://bit.ly/3cTLh4q
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D)
E)
micelle activation; water-salt interface
none of the above
Section: 20.1.A
Level of Difficulty: Moderate
Learning Objective: Lipid Digestion, Absorption, and Transport
19. Which of the following accurately ranks lipoproteins from highest to lowest density?
A)
B)
C)
D)
E)
chylomicrons > HDL > LDL > IDL > VLDL
HDL > IDL > LDL > VLDL > chylomicrons
HDL > LDL > IDL > VLDL > chylomicrons
chylomicrons > VLDL > IDL > LDL > HDL
VLDL > IDL > LDL > HDL > chylomicrons
Section:
20.1.B
Level of Difficulty: Moderate
Learning Objective: Lipid Digestion, Absorption, and Transport
Which of the following statements about apolipoproteins (with the possible exception of apoB-100) is TRUE?
Answers available at http://bit.ly/3cTLh4q
20.
I. The apolipoproteins are water-soluble and loosely associate with the lipoproteins.
II. The apolipoproteins contain helices with hydrophobic and hydrophilic groups on opposite
sides of the helical cylinder.
III. The apolipoproteins are synthesized in the intestinal tissues.
IV. The apolipoproteins appear to float on the surface of phospholipids.
A)
I only
B)
I and II
C)
III, IV
D)
I, II, III
E)
I, II, IV
Section: 20.1.B
Level of Difficulty: Moderate
Learning Objective: Lipid Digestion, Absorption, and Transport
21. Knoop’s experiments with fatty acids
A)
B)
C)
involved the novel use of chemical labels to elucidate metabolic mechanisms.
demonstrated that fatty acids are broken down by two carbons at a time by oxidation
at the ω carbon.
demonstrated a distinct difference in the mechanism of odd chain versus. even chain
fatty acid oxidation.
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D)
E)
A and B
A, B, and C
Section: 20.2
Level of Difficulty: Difficult
Learning Objective: Fatty Acid Oxidation
22. Which of the following statements about peroxisomes is FALSE?
A)
B)
C)
D)
oxidation in peroxisomes can shorten very long fatty acids.
Mammalian peroxisomes can synthesize some lipids, including bile salts.
In plants, peroxisomes and glyoxysomes serve as the site of oxidation.
Long chain fatty acids are transported into the peroxisome via a carnitine carrier
protein where they are activated for oxidation.
oxidation in peroxisomes varies slightly from the mitochondrial process.
E)
Section:
20.2.F
Level of Difficulty: Difficult
Learning Objective: Fatty Acid Oxidation
23. An important structural lipid found in nerve cell membranes,
A)
B)
C)
D)
E)
, is a type of
.
sphingomyelin, phospholipid
phosphatidylcholine, phospholipid
palmitate, glycerophospholipid
glucagon, hormone
none of the above
Section:
20.6.B
Level of Difficulty: Moderate
Learning Objective: Synthesis of Other Lipids
24. Pain and inflammation are triggered by
A)
B)
C)
D)
E)
which are synthesized by an enzyme inhibited by
cardiolipins; aspirin
prostaglandins; aspirin
analgesics; statins
prostaglandins; COX-1
cyclooxygen; NSAIDS
Section:
20.6.C
Level of Difficulty: Moderate
Learning Objective: Synthesis of Other Lipids
Answers available at http://bit.ly/3cTLh4q
25. Cholesterol is a precursor to
I. prostaglandins
II. vitamin K
III. steroid hormones such as androgens
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.
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IV. bile acids
A)
I, III, IV
B)
I, II, III, IV
C)
III only
D)
IV only
E)
III, IV
Section:
20.7
Level of Difficulty: Easy
Learning Objective: Cholesterol Metabolism
26. Which of the following best describes arachidonic acid?
A)
B)
C)
D)
E)
a 20-carbon isoprene-based intermediate of cholesterol synthesis
a 20-carbon fatty acid essential for cholesterol synthesis
a 20-carbon isoprene-based compound used for synthesis of prostaglandins
a 20-carbon fatty acid used for synthesis of prostaglandins
a 2-carbon compound that functions in conjunction with a fatty acid carrier protein
for transport of primed fatty acids
Section:
20.6.C
Level of Difficulty: Easy
Learning Objective: Synthesis of Other Lipids
Answers available at http://bit.ly/3cTLh4q
27. Which of the following compounds are required to make sphingosine?
I. palmitoyl-CoA
II. serine
III. acetyl-CoA
IV. isoprene
V. arachidonic acid
A)
I, II
B)
I, III
C)
II, IV
D)
IV, V
E)
II, V
Section:
20.6.B
Level of Difficulty: Moderate
Learning Objective: Synthesis of Other Lipids
28. In which location listed below does the following reaction take place?
A)
B)
C)
D)
HMG-CoA → acetoacetate + Acetyl-CoA
cytosol of cardiomyocytes
mitochondria of cardiomyocytes
cytosol of liver cells
mitochondria of liver cells
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E)
all of the above
Section: 20.3
Level of Difficulty: Moderate
Learning Objective: Ketone Bodies
Answers available at http://bit.ly/3cTLh4q
29. In which cellular compartment does the following reaction take place?
A)
B)
C)
D)
E)
HMG-CoA + 2 NADPH → mevalonate + 2 NADP+ + Acetyl-CoA
cytosol of liver cells
mitochondria of liver cells
cells in the intestinal lumen
lysosomal fluid
all of the above
Section:
20.7.A
Level of Difficulty: Moderate
Learning Objective: Cholesterol Metabolism
30. Which enzyme catalyses the key regulatory step of cholesterol synthesis?
A)
B)
C)
D)
E)
-ketothiolase
HMG-CoA synthase
HMG-CoA reductase
mevalonate-5-phosphotransferase
phenyltransferase
Section:
20.7.A
Level of Difficulty: Easy
Learning Objective: Cholesterol Metabolism
Answers available at http://bit.ly/3cTLh4q
31. Sphinganine is an intermediate in the synthesis of which of the following?
I. ceramides
II. spingomyelins
III. cerebrosides
IV. prostaglandins
A)
I only
B)
I, II
C)
I, II, III
D)
II, III
E)
I, II, IV
Section:
20.6.B
Level of Difficulty: Difficult
Learning Objective: Synthesis of Other Lipids
Answers available at http://bit.ly/3cTLh4q
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32. Which of the following is TRUE regarding the enzyme acetyl-CoA carboxylase?
I. It catalyzes the first committed step in fatty acid oxidation.
II. It requires S-adenosylmethionine.
III. It produces malonyl CoA
IV. It uses acetyl CoA
A)
I, II, III, IV
B)
I only
C)
I, III, IV
D)
III, IV
E)
III only
Section:
20.4.B
Level of Difficulty: Difficult
Learning Objective: Fatty Acid Biosynthesis
33. What is the net production of ATP from complete catabolism of the following fatty acid to CO2 and
H2O?
A)
B)
C)
D)
E)
< 50
51 – 90
91 - 120
121 - 150
151 +
Section: 20.4.B
Level of Difficulty: Moderate
Learning Objective: Fatty Acid Biosynthesis
34. Which of the following could be produced by the reaction of two or more of phosphatidic acids with
two or more glycerol-3-phosphates?
I. phosphatidylglycerol
II. cardiolipin
III. phosphatidylinositol
IV. gangliosides
A)
I, II, III, IV
B)
II, III
C)
I, III
D)
I, II
E)
III only
Answers available at http://bit.ly/3cTLh4q
Section:
20.6.A
Level of Difficulty: Difficult
Learning Objective: Synthesis of Other Lipids
35. The mechanism of the condensing enzyme (KS) of fatty acid synthase is best described as
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A)
B)
C)
D)
E)
base catalysis using a glu residue in the active site
acid catalysis using a glu residue in the active site
base catalysis using a cys residue in the active site
acid catalysis using a cys residue in the active site
covalent catalysis using a cys residue in the active site
Section: 20.4.C
Level of Difficulty: Difficult
Learning Objective: Fatty Acid Biosynthesis
36. Which statement concerning fatty acid synthesis is TRUE?
I. The process occurs in the cytosol.
II. In eukaryotes, the process occurs on a single large protein.
III. The growing acyl chain is carried on an acyl carrier protein instead of coenzyme A.
IV. The process requires two NADPH per acetyl group (2 carbons) added.
A)
I, II
B)
II, III
C)
I, II, III, IV
D)
III, IV
E)
I, III, IV
Section:
20.4.C
Level of Difficulty: Moderate
Learning Objective: Fatty Acid Biosynthesis
37. Which of the following diets would most likely promote the formation of ketone bodies?
A)
B)
C)
D)
E)
high simple carbohydrates, low fat
high complex carbohydrates, high fructose
high fat, high protein, low carbohydrate
low fat, high protein, high complex carbohydrates
high fructose; high whole grain carbohydrates
Section:
20.3
Level of Difficulty: Difficult
Learning Objective: Ketone Bodies
Answers available at http://bit.ly/3cTLh4q
38. Which statement concerning phospholipid synthesis is true?
A)
B)
C)
D)
E)
Addition of polar “head groups” to diacylglycerol usually involves CDP derivatives.
Addition of polar “head groups” to diacylglycerol usually involves UDP adducts.
Addition of fatty acyl “tails” to glycerol usually involves CDP adducts.
Addition of fatty acyl “tails” to glycerol usually involves UDP adducts.
None of the above is true.
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Section: 20.6.A
Level of Difficulty: moderate
Learning Objective: Synthesis of Other Lipids
39. An enzyme that is inhibited by the statin group of drugs (e.g. Lipitor®) is
A)
B)
C)
D)
E)
phospholipase a2.
hormone sensitive lipase.
HMG CoA reductase.
desaturase.
glycerol kinase.
Section:
20.7
Level of Difficulty: Easy
Learning Objective: Cholesterol Metabolism
40. Which of the following is the source of the two carbon fragments in fatty acids biosynthesis?
A)
B)
C)
D)
E)
acetyl CoA
malonyl CoA
palmitic acid
propionyl CoA
ceramides
Section:
20.4.C
Level of Difficulty: Easy
Learning Objective: Fatty Acid Biosynthesis
Answers available at http://bit.ly/3cTLh4q
41. Which of the following is the starting metabolite in ketone body biosynthesis?
A)
B)
C)
D)
E)
acetyl CoA
malonyl CoA
propionlyl CoA
acetyl CoA and propionyl CoA
acetyl CoA and malonyl CoA
Section:
20.3
Level of Difficulty:
Learning Objective: Ketone Bodies
Answers available at http://bit.ly/3cTLh4q
42. Which of the following is FALSE regarding HMG-CoA reductase?
A)
B)
C)
D)
HMG-CoA reductase is highly regulated.
The active site is tightly bound by statins.
HMG-CoA reductase levels are increased as a result of high cholesterol
concentrations in the ER
HMG-CoA reductase levels are decreased as a result of high cholesterol
concentrations in the ER.
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E)
HMG-CoA reductase is levels are decreased by the same factor that down regulated
production of the LDL receptors
Section: 20.7.A.B
Level of Difficulty: Moderate
Learning Objective: Cholesterol Metabolism
43. Considering the figure below, what compound would be formed by action of acyl-CoA
dehydrogenase?
A)
B)
C)
D)
E)
Section:
20.2.C
Level of Difficulty: Moderate
Learning Objective: Fatty Acid Oxidation
Answers available at http://bit.ly/3cTLh4q
44. Which of the following drugs acts by acetylating a serine residue preventing adequate enzyme
activity?
A)
B)
C)
D)
E)
ibuprofen
acetaminophen
Vioxx®
aspirin
Celebrex®
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Section:
20.6.C
Level of Difficulty: Easy
Learning Objective: Synthesis of Other Lipids
45. PGH2 is synthesized from
A)
B)
C)
D)
E)
and triggers pain and
.
cardiolipins; foam cell development
steroids; fever
salicylic acid; foam cell development
NSAIDS; COX-1
arachidonate; inflammation
Section:
20.6.C
Level of Difficulty: Easy
Learning Objective: Synthesis of Other Lipids
46. Which of the following enzymes is NOT involved in the tricarboxylate transport system?
A)
B)
C)
D)
E)
citrate synthase
ATP citrate lyase
malate dehydrogenase
malic enzyme
All are involved in the transport of acetyl-CoA into the cytosol
Section:
20.4.A
Level of Difficulty: Easy
Learning Objective: Fatty Acid Biosynthesis
47. Which of the following components would be condensed to form acetoacetate?
A)
B)
C)
D)
E)
acetyl CoA and acetyl-CoA
HMG-CoA and acyl-CoA
acetone and betahydroxybutyrate
malonyl-CoA and acyl-CoA
DHAP and glycerol-3-phosphate
Section:
20.3
Level of Difficulty: Easy
Learning Objective: Ketone Bodies
48. Which of the following is the correct sequence of events in cholesterol synthesis? (Note: not all
events in the sequence are included)
A)
B)
C)
D)
HMG-CoA > isopentyl pyrophosphate > farnesyl pyrophosphate > geranyl
pyrophosphate
isopentyl pyrophosphate > squalene > oxidosqualene > geranyl pyrophosphate
dimethylallyl pyrophosphate > geranyl pyrophosphate > farnesyl pyrophosphate >
squalene
HMG –CoA > phosphomevalonate > squalene > farnesyl pyrophosphate
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E)
mevalonate > dimethylallyl pyrophosphate > farnesyl pyrophosphate > gernayl
pyrophosphate
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Section: 20.7
Level of Difficulty: Difficult
Learning Objective: Cholesterol Metabolism
49. Which of the following compounds is produced by the multistep cyclization of squalene?
A)
B)
C)
D)
E)
lanosterol
geranyl pyrophosphate
fanesyl pyrophosphate
isoprene
isopentyl pyrophosphate
Section:
20.7
Level of Difficulty: Easy
Learning Objective: Cholesterol Metabolism
50. Which of the following is NOT an example of a problem sometimes associated with unsaturated fatty
acid breakdown?
A)
B)
C)
D)
E)
β, double bond
α, β double bond
unanticipated isomerization
inhibition of hydratase by a double bond
All of the above are problems.
Section:
20.2.D
Level of Difficulty: Moderate
Learning Objective: Fatty Acid Oxidation
51. LDL taken up by the liver is
A)
B)
C)
D)
E)
broken down into fatty acids and amino acids.
taken up by the ER and used to control synthesis of HMG CoA reductase and LDL
receptor synthesis.
converted into clathrin and recycled.
irreversibly bound to LDL receptors.
excreted in a clathrin coated vesicle.
Answers available at http://bit.ly/3cTLh4q
Section: 20.2.B
Level of Difficulty: Moderate
Learning Objective: Lipid Digestion, Absorption, and Transport
Answers available at http://bit.ly/3cTLh4q