Chapter 27 Fatty Acid Degradation
Matching Questions
Use the following to answer questions 1–10:
Choose the correct answer from the list below. Not all of the answers will be used.
a) pyrophosphate
b) 106 ATP
c) pyruvate dehydrogenase
d) oxidation
e) glucagon
f) glycolysis
g) 30 ATP
h) cobalamin
i) hydroxybutyrate
j) hormone-sensitive lipase
k) oxaloacetate
l) adipose
m) acyl CoA dehydrogenase
1.
Triacylglycerols are stored in ____________ cells in animals.
2.
The approximate energy yield from complete oxidation of palmitate is ____________.
Ans: b
3.
The molecule ____________stimulates lipolysis when energy reserves are low.
Ans: e
Section: 27.1
4.
The enzyme ____________ is activated by hormones and is responsible for the first hydrolysis
of triacylglycerol.
Ans: j.
Section: 27.1
5.
The transfer of an acyl group to coenzyme A is driven by the hydrolysis of ____________.
Ans: a
Section: 27.1
6.
The pathway by which an acyl CoA is degraded to acetyl CoA is ____________.
Ans: d
Section: 27.1
7.
Another name for vitamin B12 is ____________.
Section: 27.2
Ans: l
Chapter 27 Fatty Acid Degradation
2
8.
The availability of the metabolite ____________ determines whether acetyl CoA, made from
fatty acids, can enter the citric acid cycle.
9.
The compound ____________ is considered one of the “ketone bodies.”
Ans: i
Section: 27.3
10.
Increases in acetyl CoA during starvation inhibit the enzyme ____________.
Ans: c
Section: 27.4
Fill–in-the-Blank Questions
11.
In eukaryotes, the degradation of fatty acids occurs in the _____.
Ans: mitochondrial matrix Section: 27.1
12.
The first step of oxidation is a(n) _____-linked oxidation of the fatty acyl chain.
Ans: FAD Section: 27.1
13.
Glucagon and _____ stimulate the breakdown of triacylglycerols by activation of a hormone-
sensitive lipase.
Ans: epinephrine Section: 27.1
14.
oxidation of odd-numbered fatty acids produces acetyl CoA and _____.
Ans: propionyl CoA Section: 27.2
15.
The final step of each round of oxidation of fatty acids is the _____ cleavage to yield acetyl
CoA.
Ans: thyolytic Section: 27.1
16.
_____ from fatty acid oxidation may enter glycolysis after phosphorylation and oxidation.
Ans: Glycerol Section: 27.1
17.
Acetoacetate spontaneously decarboxylates to form _____.
Ans: acetone Section: 27.3
18.
The brain uses _____ instead of glucose for its source of ATP production during long-term
fasting.
Ans: ketone bodies Section: 27.4
19.
Acetoacetate and _____are referred to as ketone bodies and are a major fuel source for muscle
tissue.
Ans: β hydroxybutyrate Section: 27.4
20.
Untreated, chronic ketone body production will_____blood pH levels.
Ans: lower Section: 27.4
Ans: k
Section: 27.3
Chapter 27 Fatty Acid Degradation
3
Multiple-Choice Questions
21.
Fatty acids are the building blocks of
A)
cholesterol.
B)
phospholipids.
C)
glycolipids.
D)
B and C.
E)
A, B, and C.
22.
Enzymes that digest the triacylglycerols into free fatty acids and monoacylglycerol are called
A)
hydrases.
B)
glyases.
C)
lipases.
D)
All of the above.
E)
None of the above.
Ans: C Section: 27.1
23.
The hormone __________ induces lipolysis, whereas the hormone __________ inhibits the
process.
A)
epinephrine; adrenocorticotropic hormone
B)
glucagon; insulin
C)
insulin; norepinephrine
D)
glucagon; epinephrine
E)
epinephrine; glucagon
Ans: B Section: 27.1
24.
The enzyme acyl CoA synthetase catalyzes
A)
lipolysis to release free glyceraldehyde.
B)
ATP-dependent reduction prior to activation.
C)
ATP-dependent activation of fatty acids using CoA.
D)
All of the above.
E)
None of the above.
Ans: C Section: 27.1
25.
Coenzyme(s) involved in the degradation of saturated fatty acyl CoA include(s)
A)
FAD.
B)
NAD+.
C)
TPP.
D)
A and B.
E)
A, B, and C.
Ans: D Section: 27.1
Ans: D Section: Introduction
Chapter 27 Fatty Acid Degradation
4
26.
The oxidation of myristyl-CoA (14:0) yields
A)
7 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+.
B)
6 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+.
C)
7 acetyl CoA + 6 FADH2 + 6 NADH + 6 H+.
D)
7 acetyl CoA + 7 FAD + 7 NAD+.
E)
14 acetyl CoA + 12 FADH2 + 12 NADH + 12 H+.
27.
How many rounds of oxidation would be required for a 16-carbon fatty acyl chain to be
degraded to acetyl CoA?
A)
16
B)
8
C)
7
D)
15
E)
None of the above.
Ans: C Section: 27.1
28.
In the conversion of propionyl CoA to succinyl CoA, what type of reaction does the cobalamin-
containing enzyme catalyze?
A)
intramolecular rearrangements
B)
methylations
C)
reduction of ribonucleotides to deoxyribonucleotides
D)
A and C
E)
A, B, and C
Ans: E Section: 27.2
29.
Odd-numbered unsaturated fatty acids are metabolized by which of the following enzymes?
A)
propionyl CoA carboxylase
B)
2,4-dienoyl reductase
C)
enoyl-CoA isomerase
D)
All of the above.
E)
None of the above.
Ans: C Section: 27.2
30.
Which organs or tissues prefer to use ketone bodies such as acetoacetate as a fuel energy source
instead of glucose?
A)
the heart muscle
B)
the renal cortex
C)
the brain
D)
A and B
E)
A, B, and C
Ans: D Section: 27.3
31.
Triacylglycerol stored in adipose tissue is used by the liver and other tissues for
A)
glycerol for pyruvate and glucose in liver.
B)
ATP production via the citric acid cycle in muscle.
C)
conversion to acetyl CoA and ketone bodies during starvation for the brain.
D)
All of the above.
E)
None of the above.
Ans: D Section: 27.1
Ans: C Section: 27.1
Chapter 27 Fatty Acid Degradation
5
32.
What does muscle weakness and cramping affecting skeletal muscle, heart, and kidney likely
indicate?
A)
carnitine excess in the diet
B)
loss of hormone-sensitive lipase activity
C)
malfunctioning or deficient carnitine translocase
D)
ketone-body production
E)
All of the above.
33.
Three rounds of fatty acid oxidation result in
A)
two acetyl CoA molecules.
B)
three acetyl CoA molecules.
C)
the synthesis of palmitate.
D)
the formation of enoyl CoA.
E)
the complete oxidation of palmitate B.
Ans: B Section: 27.1
34.
The activation of fatty acids for degradation takes place in two steps. What is the intermediate
formed and why is activation necessary for β oxidation to occur?
A)
Acyl adenlyate; the cAMP formed by this reaction activates protein kinase A.
B)
Acyl adenlyate; only the activated form of the fatty acid can react with coenzyme A.
C)
Propionate; only the activated form of the fatty acid can react with coenzyme A.
D)
Acyl carnitine; the cAMP formed by this reaction activates protein kinase A.
E)
Acyl carnitine: this intermediate is needed to fuel the carnitine cycle.
Ans: B Section: 27.1
35.
Exercising first thing in the morning without eating mobilizes lipid stores for fuel. All of the
below are involved in this mobilization, EXCEPT
A)
glucagon binds 7TM receptors that activate adenylate cyclase.
B)
perilipin is phosphorylated.
C)
cAMP stimulates protein kinase A.
D)
hormone-sensitive lipase completes the mobilization of fatty acids with the production of
a free fatty acid and glycerol.
E)
hormone-sensitive lipase is phosphorylated.
Ans: D Section: 27.1
36.
What is the role of acetoacetate in lipid metabolism in addition to providing energy when blood
glucose is low?
A)
B)
C)
D)
E)
Ans: E Section: 27.3
Ans: C Section: 27.1
Chapter 27 Fatty Acid Degradation
6
37.
How does the formation of acetyl CoA by β oxidation not only provide energy for cellular
respiration, but also spare glucose?
A)
As acetyl CoA levels increase during lipid metabolism, D-3-hydroxybutyrate is reduced to
pyruvate for gluconeogenesis.
B)
Acetyl CoA provides carbon for the formation of oxaloacetate, which in turn can be
decarboxylated to form pyruvate.
C)
Acetyl can be converted to acetoacetate and from there to lactate for anaerobic
metabolism.
D)
Acetyl CoA derived from fatty acids inhibits pyruvate dehydrogenase, the enzyme that
converts pyruvate into acetyl CoA.
E)
Acetyl CoA derived from fatty acids activates pyruvate carboxylase stimulating
gluconeogenesis.
38.
Every biochemistry student knows that most naturally occurring unsaturated fatty acids are “cis”
fatty acids. Why then do so many fat-containing foods come with the notation “Contains no
trans fats”?
A)
Vegetable oils contain polyunsaturated fatty acids prone to oxidation, which then convert
them to trans fats.
B)
Olive oils, normally healthy oils, are converted to trans fat when cooked at high
temperatures. Thus, olive oils are used only at low temperatures.
C)
Vegetable oils are often hydrogenated to form trans unsaturated fatty acids to preserve
shelf life.
D)
Oils that contain an odd number of carbon atoms are particularly susceptible to oxidation
to trans fats. Thus, no odd numbered carbon fatty acids are used in these foods.
E)
Oils that contain an odd number of carbon atoms are particularly susceptible to reduction
to trans fats. Thus, no odd number carbon fatty acids are used in these foods.
Ans: C Section: 27.4
Short-Answer Questions
39.
How and where are fatty acids stored?
Ans:
Fatty acids are stored as triacylglycerol in adipocytes of adipose tissue. This fuel-rich
tissue can be found under the skin (subcutaneous) or surrounding internal organs
(visceral).
Section: Introduction
40.
What are the repeated steps of fatty acid degradation?
and finally, thiolysis. These are detailed in steps 3–6 in Table 27.1.
Section: 27.1
Ans: D Section: 27.4
Chapter 27 Fatty Acid Degradation
7
41.
Briefly outline the steps in fatty acid degradation.
42.
Why is the anhydrous nature of triacylglycerols important in energy efficiency?
carbohydrates, gram for gram.
Section: 27.1
43.
What three stages are required to utilize the energy stores in adipocytes?
processed in the citric acid cycle.
Section: 27.1
44.
What is the fate of glycerol released during lipolysis?
pyruvate.
Section: 27.1
45.
How is pyrophosphate formation an important theme in biochemistry?
a common strategy in several paths.
Section: 27.1
46.
Calculate the amount of ATP generated from the total oxidation of an activated fatty acid with
an acyl chain of 16 carbons.
activation. The net amount generated is therefore 106 ATP.
Section: 27.1
molecule of acetyl CoA.
Section: 27.1
Chapter 27 Fatty Acid Degradation
8
47.
How are unsaturated fatty acids degraded?
48.
In odd-numbered fatty acid chains, how is the final three-carbon piece, propionyl CoA, utilized?
49.
What pathological conditions can arise from a large increase in blood levels of ketone bodies in
diabetics?
tissue function.
Section: 27.4
50.
Explain why animals cannot convert fatty acids to glucose.
possess the glyoxylate cycle, which can convert two acetyl groups into succinate.
51.
What organelle contains the enzymes for β oxidation and how does the fatty acid enter this
organelle?
carnitine into the matrix while transporting carnitine back out.
Section: 27.2