Lipid Metabolism Flashcards

1
Q

Phospholipases are designated A, B, etc, based on
a. the different sites in the molecule where they cleave the phospholipids.
b. whether they are phosphorylases or hydrolases.
c. whether they use NAD as a cofactor.
d. whether they use ATP as a cofactor.

A

a

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2
Q

Phospholipases break down fats by
a. adding a phosphate group to them.
b. reducing the double bonds to single bonds.
c. hydrolyzing them.
d. removing acetyl-CoA units.
e. none of these

A

c

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3
Q

Which of the following is true concerning phospholipases?
a. Many snake venoms contain phospholipases
b. Phospholipase D is a component in some spider venoms
c. Phospholipases in snake venoms can lead to the lysing of blood cells
d. All of these

A

d

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4
Q

The bond linking a fatty acid to coenzyme A is
a. an ester.
b. a thioester.
c. an anhydride.
d. an ether.
e. none of these

A

b

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5
Q

Which of the following statements below about the activation of fatty acids is false?

a. Activation involves the formation of a high energy thioester bond.

b. Activation is accompanied by hydrolysis of ATP to ADP and Pi.

c. Activation includes the formation of an acyl-adenylate intermediate.

d. Activation includes hydrolysis of ATP to produce AMP and PPi, with the further hydrolysis of PPi to drive the reaction to completion

A

b

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6
Q

The carrier molecule which transports fatty acids through the inner mitochondrial membrane is
a. ATP.
b. Carnitine.
c. Coenzyme A.
d. Lipoic Acid.
e. none of these

A

b

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7
Q

Which of the following reactions is catalyzed by carnitine acyltransferase?
a. carnitine + acyl-CoA –> CoASH + acylcarnitine
b. CoASH + acylcarnitine –> carnitine + acyl-CoA
c. both of these
d. none of these

A

c

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8
Q

Which of the following is not true regarding catabolism of triacylglycerols?
a. Control of release of fatty acids from triacylglycerols in adipocytes involves cyclic AMP as a second
messenger.
b. When cAMP is a second messenger in the catabolsim of triacylglycerols, it activates a protein kinase
c. The protein kinase, once activated, cleaves fatty acids from the triacylglycerol
d. The phosphorylated form of triacylglycerol lipase is the active form
e. All of these are true

A

c

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9
Q

The use of cyclic AMP to mobilize fatty acids from adipose tissue is analogous to cyclic AMPs role in mobilization of
sugars from glycogen in the liver.
a. True
b. False

A

a

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10
Q

Which of the following statements concerning β-oxidation of fatty acids is false?
a. Initiation occurs at the methyl end of the fatty acid.
b. β-oxidation is the primary route for degradation of fatty acids.
c. β-oxidation takes place in the mitochondrial matrix.
d. Two-carbon units are successively eliminated with each round.

A

a

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11
Q

The metabolically activated form of a fatty acid is
a. an ester
b. a Schiff base
c. a phosphate ester
d. a thioester
e. none of these

A

d

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12
Q

Where in the cell does β-oxidation occur?
a. Cytoplasm.
b. Outer mitochondrial membrane.
c. Mitochondrial intermembrane space.
d. Inner mitochondrial membrane.
e. Mitochondrial matrix.

A

e

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13
Q

When an acyl group is being transferred from the cytosol to the mitochondria for oxidation, the order of the enzymes it
encounters is:
a. CPT-I: Carnitine Translocase: CPT-II
b. Carnitine Translocase: CPT-I: CPT-II
c. CPT-II: Carnitine Translocase: CPT-I
d. none of these

A

a

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14
Q

Which of the following best describes carnitine?
a. It transports fatty acids across the inner mitochondrial membrane for breakdown.
b. It transports acetyl-CoA to the cytosol for fatty acid synthesis.
c. It’s a precursor of cholesterol.
d. It carries growing acyl chains during fatty acid synthesis.
e. none of these

A

a

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15
Q

Carnitine acyltransferase is located in the mitochondrial
a. intermembrane space.
b. outer membrane.
c. inner membrane.
d. matrix.

A

c

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16
Q
  1. The enzyme activity catalyzing the reaction shown is best termed a

(picture)

a. reductase
b. hydratase
c. dehydratase
d. dehydrogenase

A

d

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17
Q
  1. Which group of small molecules best fit the boxes associated with the reaction shown?

(picture)

 a                        b I. ATP                   ADP II. NAD+              NADH III. NADP+           NADPH IV. FAD                FADH2
A

b

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18
Q

The first three reactions of the β-oxidation cycle of fatty acids produce
a. two moles of NADH
b. two moles of FADH2
c. one mole each of NADH and FADH2
d. two moles of ATP

A

c

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19
Q

Which of the following is not a product of the activation of fatty acids?
a. A thioester
b. ADP
c. Pyrophosphate
d. Phosphate
e. All of these are products of the activation of a fatty acid.

A

b

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20
Q

Fatty acid catabolism is called β-oxidation, since the second or β carbon from the carboxyl group is the site of
oxidation.
a. True
b. False

A

a

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21
Q

Palmitic acid, with 16 carbons, requires 8 cycles of β-oxidation to produce 8 acetyl-CoA.
a. True
b. False

A

b

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22
Q

How many cycles of β-oxidation are required to convert stearic acid (18 carbons) to 9 acetyl-CoAs?
a. 6
b. 8
c. 9
d. 18
e. none of these

A

b

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23
Q

The reactions involved in β-oxidation of fatty acids include the following:
1. Cleavage of acetyl-CoA from the fatty acid.
2. Hydration of a double bond.
3. Formation of a C−C double bond.
4. Oxidation of an alcohol.
The correct order of these reactions is:
a. 1 → 2 → 3 → 4
b. 4 → 3 → 2 → 1
c. 3 → 2 → 4 → 1
d. 2 → 4 → 3 → 1
e. 1 → 4 → 3 → 2

A

c

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24
Q

Which of the following vitamins and cofactors is not used in β-oxidation?
a. Biotin
b. Niacin
c. Pantothenic acid
d. Riboflavin
e. All of these are important in the β-oxidation of fatty acids.

A

a

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25
Q

How many NAD+
are reduced in the degradation of palmitoyl-CoA to form eight molecules of acetyl-CoA?
a. 1
b. 7
c. 8
d. 14
e. 16

A

b

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26
Q

Which of the following is true about the oxidation steps in β-oxidation of fatty acids?
a. NAD+
is the cosubstrate when the oxidation creates a double bond
b. FAD is the cosubstrate when the oxidation produces a carbonyl group
c. FAD is the cosubstrate when the oxidation creates a double bond
d. either NAD+
or FAD can be used to create a double bond
e. none of these

A

c

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27
Q

The processing of one molecule of stearic acid (18 carbons) by β-oxidation
a. requires 8 cycles of β-oxidation and produces 9 molecules of acetyl-CoA.
b. requires 8 cycles of β-oxidation and produces 8 molecules of acetyl-CoA.
c. requires 9 cycles of β-oxidation and produces 8 molecules of acetyl-CoA.
d. requires 9 cycles of β-oxidation and produces 9 molecules of acetyl-CoA

A

a

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28
Q

How many ATPs can be netted from the complete oxidation of palmitate (C16) to CO2 & H2O?
a. ATPs ≤ 40
b. 40 < ATPs ≤ 80
c. 80 < ATPs ≤ 120
d. 1200 < ATPs

A

c

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29
Q

Approximately how many ATP molecules are netted from the complete oxidation of stearic acid (C−18)?
a. 2
b. 4
c. 32
d. 88
e. 120

A

e

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30
Q

Lipids yield more ATP than sugars because
a. they have more carbon atoms than sugars.
b. their carbon atoms are more highly reduced.
c. both of these
d. neither of these

A

c

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31
Q

Which of the following is not true?
a. One advantage of the β-oxidation of fats compared to oxidation of sugars is that fatty acids produce more
metabolic water.
b. The oxidation of fats produces more energy per carbon than the oxidation of carbohydrates
c. Fat yields more energy than carbohydrates because it is more oxidized
d. For every cycle of oxidation of a fatty acid, one NADH and one FADH2 are produced

A

c

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32
Q

Which of the following is not an advantage of fatty acids as a form of energy storage?
a. Fatty acids contain more highly reduced carbons than carbohydrates.
b. Their hydrophobic nature allows close packing in adipose tissue.
c. Storage of fats in muscle tissue makes it readily available for use during activity.
d. Fats contain more energy per gram than sugars.
e. They do not require water for storage.

A

c

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33
Q

The oxidation of unsaturated fatty acids specifically requires
a. a cis-trans isomerase and a reductase.
b. a cis-trans isomerase and a dehydrogenase.
c. a dehydrogenase and a reductase.
d. a dehydrogenase and a hydrase.
e. none of these

A

a

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34
Q

A key intermediate in the catabolism of fatty acids with uneven numbers of carbon atoms is
a. malonyl-CoA
b. propionyl-CoA
c. oxaloacetate
d. phosphoenolpyruvate

A

b

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35
Q

The β-oxidation of fatty acids with an odd number of carbons requires additional enzymes to allow all the products to
enter the citric acid cycle .
a. True
b. False

A

a

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36
Q

When is propionyl-CoA carboxylase required for the complete oxidation of a fatty acid?
a. When it has an even number of carbons.
b. When it has an odd number of carbons.
c. When it is a monounsaturated fatty acid.
d. When it is a polyunsaturated fatty acid.
e. Never

A

b

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37
Q

The conversion of methylmalonyl-CoA to succinyl-CoA involves which of these cofactors?
a. thiamine pyrophosphate
b. Vitamin B12
c. NAD
d. biotin

A

b

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38
Q

The oxidation of an unsaturated fatty acid leads to the production of fewer ATPs than a saturated fatty acid with the same number of carbons because ____

a. the oxidation of the fatty acid stops when it reaches the double bond
b. unsaturated fatty acids cannot be metabolized
c. the double bond results in the bypassing of the first oxidation step of the pathway, thereby eliminating one
FADH product
d. none of these

A

c

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39
Q

The cis double bonds of naturally-occurring fatty acids react well with the hydratase enzyme.
a. True
b. False

A

b

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40
Q

The β-oxidation of unsaturated fatty acids requires additional enzymes to isomerize the double bonds.
a. True
b. False

A

a

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41
Q

The unsaturated fatty acids that are intermediates in the β-oxidation cycle have what orientation around the double
bond?
a. the cis orientation
b. the trans orientation
c. can have either orientation
d. the orientation is not known

A

b

42
Q

Isomerization of the double bonds of polyunsaturated fatty acids involves both cis-trans isomerization and changing
the position of the double bonds.
a. True
b. False

A

a

43
Q

The yield of ATP from oxidation of an unsaturated fatty acid has what relationship to the yield from the oxidation of a
saturated fatty acid with the same number of carbon atoms?
a. less
b. greater
c. the same
d. not possible to determine from the information in this chapter

A

a

44
Q

A key intermediate in the formation of “ketone bodies” is
a. succinyl-CoA
b. methyl malonyl-CoA
c. propionyl-CoA
d. acetoacetyl-CoA

A

d

45
Q

“Ketone bodies” are formed when
a. oxaloacetate is converted to acetoacetyl-CoA.
b. there is a deficiency of acetyl-CoA.
c. there is not enough oxaloacetate to react with available acetyl-CoA.
d. an organism consumes excessive amounts of carbohydrate compared to its lipid intake.
e. none of these

A

c

46
Q

What effect do high concentrations of ketone bodies have on blood pH?
a. They tend to lower blood pH.
b. They tend to increase blood pH.
c. They have no effect on blood pH.

A

a

47
Q

Which of the following is not true regarding ketone bodies?
a. Ketone bodies form during the catabolism of fats.
b. Ketone bodies are an effective means for weight loss, since the body will excrete them in the urine.
c. The first enzyme used in the production of ketone bodies is thiolase
d. Ketone bodies are always an alternative fuel in all tissues

A

d

48
Q

Which are the three most common ketone bodies?
a. Acetone, formaldehyde, acetoacetate.
b. Acetone, butyric acid and oxaloacetate.
c. Acetone, β-hydroxybutyrate and acetoacetate.
d. Acetone, β-hydroxybutyrate and oxaloacetate.
e. Acetocetate, β-hydroxybutyrate and oxaloacetate

A

c

49
Q

Acetyl-CoA carboxylase uses which of these cofactors?
a. thiamine pyrophosphate
b. Vitamin B12
c. NAD
d. biotin

A

d

50
Q

Where in the cell does fatty acid synthesis occur?
a. Cytoplasm.
b. Outer mitochondrial membrane.
c. Mitochondrial intermembrane space.
d. Inner mitochondrial membrane.
e. Mitochondrial matrix.

A

a

51
Q

Of the processes listed below, which is not an important source of acetyl-CoA?
a. pentose phosphate pathway
b. amino acid degradation
c. glycolysis
d. fatty acid oxidation

A

a

52
Q

How is acetyl-CoA transported from the mitochondria to the cytosol for fatty acid synthesis?
a. directly as acetyl-CoA
b. through a temporary linkage to carnitine
c. as citric acid
d. There is no reason to transport acetyl-CoA from the mitochondria to the cytosol, since it is produced primarily
in the cytosol.

A

c

53
Q

Reduction reactions during fatty acid synthesis utilize
a. FADH2.
b. NADH.
c. NADPH.
d. FADH2 and NADH.
e. FADH2 and NADPH.

A

c

54
Q

If the bicarbonate used in malonyl-CoA synthesis were labeled with 14C in the biosynthesis of palmitate, where would
the label be found in the reaction products?
a. CO2
b. C−16 of palmitate
c. C−1 of palmitate
d. evenly distributed in palmitate

A

a

55
Q

The addition of two-carbon units to a growing fatty acid chain is directly driven by
a. reduction of NADP+
b. oxidation of NADPH
c. decarboxylation of malonyl-CoA
d. hydrolysis of ATP

A

c

56
Q

Which of the following statements concerning the anabolism and catabolism of fatty acids is true?
a. Biotin is required for oxidation of fatty acids but not for anabolism.
b. NADPH is required for anabolism of fatty acids and not for catabolism.
c. Anabolism occurs in the intermembrane space of mitochondria while catabolism takes place in the
mitochondrial matrix.
d. Acetyl-CoA is not required for anabolism.

A

b

57
Q

The primary function of biotin in metabolism is:
a. to allow for the addition of CO2 to other molecules.
b. to inhibit acetyl-CoA carboxylase
c. to inhibit carnitine palmitoyltransferase
d. all of these
e. none of these

A

a

58
Q

Since acetyl-CoA carboxylase is key to the synthesis of fatty acids, inhibitors of this enzyme may be useful for weight
loss or treatment of obesity.
a. True
b. False

A

a

59
Q

Synthesis of fatty acids involves simple reversal of the β-oxidation cycle.
a. True
b. False

A

b

60
Q

Fatty acid synthase binds growing fatty acids
a. by an ester linkage to a side chain of serine.
b. by a thioester linkage to a side chain of cysteines.
c. as a Schiff base to a side chain of lysine.
d. by a thioester linkage to a phosphopantetheine linked to a serine.

A

d

61
Q
  1. Which group of small molecules best fit the boxes associated with the reaction shown?

(picture)

   a                   b I. ATP                ADP II. NAD+           NADH III. NADPH       NADP+ IV. NADH         NAD+
A

c

62
Q
  1. The enzyme activity catalyzing the reaction shown is best termed a

(picture)

a. reductase
b. ketothiolase
c. transferase
d. dehydratase

A

a

63
Q
  1. The enzyme activity catalyzing the reaction shown is best termed a

(picture)

a. reductase
b. ketothiolase
c. transferase
d. dehydratase

A

d

64
Q

The acyl carrier used in fatty acid synthesis is similar to coenzyme A.
a. True
b. False

A

a

65
Q

During fatty acid synthesis, the growing fatty acid is always bound to a protein.
a. True
b. False

A

a

66
Q

Which of the following mechanisms explains why fatty acid synthesis and breakdown do not compete with each other
in the body?
a. Synthesis and breakdown take place in two separate compartments of the cell.

b. One process uses NADH/NAD+
and the other uses NADPH/NADP+

c. They are not attached to the same carrier molecule in the two processes.

d. All of these mechanisms are in operation.

e. None of these

A

d

67
Q

How many NADPH are oxidized in the synthesis of palmitoyl-CoA from eight molecules of acetyl-CoA?
a. 1
b. 7
c. 8
d. 14
e. 16

A

d

68
Q

Compared to β-oxidation, fatty acid synthesis requires this extra vitamin or cofactor.
a. Biotin
b. Riboflavin
c. Niacin
d. Pantothenic acid
e. All of these are used in both pathways.

A

a

69
Q

Which of the following reactants is involved in both fatty acids synthesis and breakdown?
a. CO2.
b. Malonyl-CoA
c. NADPH.
d. Pantothenic acid.
e. All of these reactants are involved in both fatty acid synthesis and breakdown.

A

d

70
Q

ACP used in fatty acid synthesis is an abbreviation for:
a. Acetyl-CoA phosphate.
b. Adenosine cyclo-phosphate.
c. Acyl Carnitine Protein
d. Acyl Carrier Protein.
e. None of these is correct.

A

d

71
Q

Which of the following enzyme types is involved in both fatty acid synthesis and breakdown?
a. Carboxylase.
b. Transferase.
c. Synthase.
d. Both carboxylase and synthase.
e. All three of these enzymes are used in fatty acid synthesis.

A

b

72
Q

Biosynthesis of compound lipids typically takes place
a. in the mitochondrial matrix
b. in the cytosol
c. on the endoplasmic reticulum
d. in the Golgi apparatus
e. none of these

A

c

73
Q

Which of the following is true about the FTO gene and obesity?
a. People with the FTO gene will be obese
b. Scientists know exactly how the FTO gene leads to obesity
c. Individuals with a specific variant of the FTO gene are a little over 1.5 times as likely to be obese
d. All of these are true

A

c

74
Q

Scientists think ACC2 may be a target to fight obesity because
a. Inhibiting ACC2 leads to lowered levels of malonyl-CoA
b. mice lacking ACC2 are leaner than wild-type mice
c. reducing malonyl-CoA relieves the inhibition of CPT-I
d. all of these

A

d

75
Q

Other than their use in nucleic acid synthesis, which energy source is used uniquely for the synthesis of lipids?
a. ATP
b. CTP
c. GTP
d. UTP
e. None of these is unique to fatty acid synthesis.

A

b

76
Q

The first committed precursor in the pathway for the synthesis of cholesterol is:
a. Isoprene
b. Lanosterol
c. Mevalonic acid
d. Squalene
e. None of these is correct.

A

c

77
Q

The ultimate precursor of all the carbon atoms in steroids is
a. acetyl-CoA (acetyl group)
b. oxaloacetate
c. succinyl-CoA (succinyl group)
d. α-ketoglutarate

A

a

78
Q

Isoprenoid derivatives play what role in steroid biosynthesis?
a. inhibit a key step
b. are key intermediates
c. compete with steroid biosynthesis for a limited precursor
d. its role is unknown

A

b

79
Q

The cyclization reaction that produces lanosterol in the course of steroid biosynthesis is remarkable because
a. it involves large molecules
b. it involves methyl groups
c. of the extreme conditions under which it takes place
d. it is a concerted reaction

A

d

80
Q

The committed step in cholesterol biosynthesis is catalyzed by
a. HMG-CoA synthase
b. HMG-CoA reductase
c. mevalonate kinase
d. squalene monooxygenase

A

b

81
Q

Cholesterol is a precursor of all of the following except
a. cortisone
b. testosterone
c. progesterone
d. lanosterol

A

d

82
Q

Drugs are available to lower cholesterol which actually inhibit its synthesis in the body.
a. True
b. False

A

a

83
Q

Lipoproteins are incorporated into the cell by a process called pinocytosis.
a. True
b. False

A

b

84
Q

Cholesterol can be made in the body; however, some must still be eaten in the diet, since we cannot make enough to
meet the demand.
a. True
b. False

A

b

85
Q

The first true steroid synthesized in the steroid pathway is the following:
a. Cholesterol.
b. Squalene
c. Lanosterol
d. Progesterone
e. Mevalonic acid

A

c

86
Q

Which of the following is not a function of cholesterol in the human body?
a. Precursor of steroid hormones.
b. Energy storage compound.
c. Precursor of bile salts.
d. Component of cell membranes.
e. All of these are important function of cholesterol in humans.

A

b

87
Q

Which of the following is not associated with coronary heart disease?
a. high relative levels of HDLs
b. high levels of LDLs
c. absence or dysfunction of LDL receptors
d. serum cholesterol levels of 300 mg/dl or higher

A

a

88
Q

When the blood contains a high concentration of LDLs, the cells respond by making fewer receptors to react with the
LDL.
a. True
b. False

A

a

89
Q

The human lipoproteins with the lowest density are
a. Chylomicrons.
b. HDL.
c. IDL.
d. LDL.
e. VLDL.

A

a

90
Q

The components of lipoproteins such as LDL and HDL which makes them water soluble are
a. proteins.
b. phospholipids.
c. unesterified cholesterol.
d. proteins and phospholipids.
e. All of these

A

d

91
Q

Which of the following are involved in the development of atherosclerosis?
a. Excess LDL
b. Inflammation
c. Adhesion molecules
d. Monocytes
e. none of these
f. all of these

A

f

92
Q

Obesity can lead to which of the following?
a. diabetes
b. heart attack
c. stroke
d. some forms of cancer
e. all of these

A

e

93
Q

Which of the following is true about neuropeptide Y?
a. it leads to increased appetite
b. it is a melanocortin
c. it leads to supressed appetite
d. It is a steroid hormone
e. none of these

A

a

94
Q

Which of the following is NOT a short term regulator of appetite?
a. ghrelin
b. Cholecystokinin
c. leptin
d. all of these are short term regulators

A

c

95
Q

Leptin is
a. a peptide hormone
b. an appetite supressant
c. a hormone that stimulates fat breakdown
d. all of these

A

d

96
Q

_____ hydrolyzes phospholipids at the surface of micelles.
a. PhospholipaseA1
b. Phospholipase D
c. Phospholipase A2
d. Phospholipase B

A

c

97
Q

Which of the following enzymes is involved in the esterification of a fatty acid for its activation?
a. Acyl-CoA synthetase
b. Pyruvate dehydrogenase
c. Aldolase
d. Phosphofructokinase

A

a

98
Q

Explain why the yield of adenosine triphosphate (ATP) from the oxidation of lipids is higher than that from carbohydrates.

A

A fatty acid is all hydrocarbon except for the carboxyl group. Therefore, a fatty acid exists in a
highly reduced state. On the other hand, a sugar is already partly oxidized because of the presence
of its oxygen-containing groups. The oxidation of a fuel leads to the reduced electron carriers to be
used in the electron transport chain. As a result, a more reduced fuel (such as a fatty acid) can be
oxidized further than a partially oxidized fuel, such as a carbohydrate.

99
Q

_____ is a condition in which arteries are blocked to a greater or lesser extent by the deposition of cholesterol
plaques.
a. Angioedema
b. Atherosclerosis
c. Anterolisthesis
d. Alkaptonuria

A

b

100
Q

Explain the involvement of leptin in the long-term control of eating behavior.

A

Leptin is a protein hormone that stimulates the breakdown of lipids and inhibits fatty acid production in adipocytes. Leptin production increases when fat deposits in adipocytes become larger, and the increased leptin is released into the bloodstream. When the signal of higher leptin levels reaches the central nervous system, there is a decrease in appetite. High levels of leptin are interpreted as overfeeding that results in a decrease in appetite. On the other hand, low leptin levels are interpreted as starvation that cause an increase in appetite.