Lipid Metabolism

Question 1

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.

Answer 1

a

Question 2

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

Answer 2

c

Question 3

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

Answer 3

d

Question 4

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

Answer 4

b

Question 5

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

Answer 5

b

Question 6

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

Answer 6

b

Question 7

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

Answer 7

c

Question 8

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

Answer 8

c

Question 9

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

Answer 9

a

Question 10

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.

Answer 10

a

Question 11

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

Answer 11

d

Question 12

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.

Answer 12

e

Question 13

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

Answer 13

a

Question 14

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

Answer 14

a

Question 15

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

Answer 15

c

Question 16

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

(picture)

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

Answer 16

d

Question 17

17. 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

Answer 17

b

Question 18

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

Answer 18

c

Question 19

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.

Answer 19

b

Question 20

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

Answer 20

a

Question 21

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

Answer 21

b

Question 22

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

Answer 22

b

Question 23

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

Answer 23

c

Question 24

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.

Answer 24

a

Question 25

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

Answer 25

b

Question 26

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

Answer 26

c

Question 27

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

Answer 27

a

Question 28

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

Answer 28

c

Question 29

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

Answer 29

e

Question 30

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

Answer 30

c

Question 31

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

Answer 31

c

Question 32

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.

Answer 32

c

Question 33

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

Answer 33

a

Question 34

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

Answer 34

b

Question 35

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

Answer 35

a

Question 36

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

Answer 36

b

Question 37

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

Answer 37

b

Question 38

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

Answer 38

c

Question 39

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

Answer 39

b

Question 40

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

Answer 40

a

Question 41

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

Answer 41

b

Question 42

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

Answer 42

a

Question 43

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

Answer 43

a

Question 44

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

Answer 44

d

Question 45

"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

Answer 45

c

Question 46

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.

Answer 46

a

Question 47

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

Answer 47

d

Question 48

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

Answer 48

c

Question 49

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

Answer 49

d

Question 50

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.

Answer 50

a

Question 51

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

Answer 51

a

Question 52

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.

Answer 52

c

Question 53

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

Answer 53

c

Question 54

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

Answer 54

a

Question 55

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

Answer 55

c

Question 56

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.

Answer 56

b

Question 57

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

Answer 57

a

Question 58

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

Answer 58

a

Question 59

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

Answer 59

b

Question 60

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.

Answer 60

d

Question 61

61. 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+

Answer 61

c

Question 62

62. The enzyme activity catalyzing the reaction shown is best termed a (picture) a. reductase b. ketothiolase c. transferase d. dehydratase

Answer 62

a

Question 63

63. The enzyme activity catalyzing the reaction shown is best termed a (picture) a. reductase b. ketothiolase c. transferase d. dehydratase

Answer 63

d

Question 64

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

Answer 64

a

Question 65

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

Answer 65

a

Question 66

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

Answer 66

d

Question 67

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

Answer 67

d

Question 68

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.

Answer 68

a

Question 69

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.

Answer 69

d

Question 70

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.

Answer 70

d

Question 71

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.

Answer 71

b

Question 72

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

Answer 72

c

Question 73

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

Answer 73

c

Question 74

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

Answer 74

d

Question 75

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.

Answer 75

b

Question 76

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.

Answer 76

c

Question 77

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

Answer 77

a

Question 78

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

Answer 78

b

Question 79

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

Answer 79

d

Question 80

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

Answer 80

b

Question 81

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

Answer 81

d

Question 82

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

Answer 82

a

Question 83

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

Answer 83

b

Question 84

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

Answer 84

b

Question 85

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

Answer 85

c

Question 86

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.

Answer 86

b

Question 87

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

Answer 87

a

Question 88

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

Answer 88

a

Question 89

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

Answer 89

a

Question 90

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

Answer 90

d

Question 91

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

Answer 91

f

Question 92

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

Answer 92

e

Question 93

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

Answer 93

a

Question 94

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

Answer 94

c

Question 95

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

Answer 95

d

Question 96

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

Answer 96

c

Question 97

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

Answer 97

a

Question 98

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

Answer 98

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.

Question 99

_____ 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

Answer 99

b

Question 100

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

Answer 100

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.