Deck 21: Lipid Metabolism

Question 1

The first three reactions of the b-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 1

C

Question 2

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 P_i.
C) Activation includes the formation of an acyl-adenylate intermediate.
D) Activation includes hydrolysis of ATP to produce AMP and PP_i, with the further hydrolysis of PP_i to drive the reaction to completion.

Answer 2

B

Question 3

Which group of small molecules best fit the boxes associated with the reaction shown?

A) I
B) II
C) III
D) IV

Answer 3

B

Question 4

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

Question 5

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.

Question 6

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

Question 7

Carnitine acyltransferase is located in the mitochondrial

A) intermembrane space.
B) outer membrane.
C) inner membrane.
D) matrix.

Question 8

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.

Question 9

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.

Question 10

Where in the cell does b-oxidation occur?

A) Cytoplasm.
B) Outer mitochondrial membrane.
C) Mitochondrial intermembrane space.
D) Inner mitochondrial membrane.
E) Mitochondrial matrix.

Question 11

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

Question 12

The bond linking a fatty acid to coenzyme A is

A) an ester.
B) a thioester.
C) an anhydride.
D) an ether.

Question 13

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.

Question 14

The metabolically activated form of a fatty acid is

A) an ester
B) a Schiff base
C) a phosphate ester
D) a thioester

Question 15

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

Question 16

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.

Question 17

The enzyme activity catalyzing the reaction shown is best termed a

A) reductase
B) hydratase
C) dehydratase
D) dehydrogenase

Question 18

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

Question 19

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

Question 20

Which of the following statements concerning b-oxidation of fatty acids is false?

A) Initiation occurs at the methyl end of the fatty acid.
B) b-oxidation is the primary route for degradation of fatty acids.
C) b-oxidation takes place in the mitochondrial matrix.
D) Two-carbon units are successively eliminated with each round.

Question 21

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

Question 22

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

Question 23

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

Question 24

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.

Question 25

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.

Question 26

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

Question 27

The conversion of methylmalonyl-CoA to succinyl-CoA involves which of these cofactors?

A) thiamine pyrophosphate
B) Vitamin B₁₂
C) NAD
D) biotin

Question 28

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

Question 29

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.

Question 30

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

Question 31

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

Question 32

The reactions involved in b-oxidation of fatty acids include the following: 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

Question 33

The processing of one molecule of stearic acid (18 carbons) by b-oxidation

A) requires 8 cycles of b-oxidation and produces 9 molecules of acetyl-CoA.
B) requires 8 cycles of b-oxidation and produces 8 molecules of acetyl-CoA.
C) requires 9 cycles of b-oxidation and produces 8 molecules of acetyl-CoA.
D) requires 9 cycles of b-oxidation and produces 9 molecules of acetyl-CoA.

Question 34

Which of the following vitamins and cofactors is not used in b-oxidation?

A) Biotin
B) Niacin
C) Pantothenic acid
D) Riboflavin
E) All of these are important in the b-oxidation of fatty acids.

Question 35

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

Question 36

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

Question 37

Which of the following is not true?

A) One advantage of the b-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

Question 38

A key intermediate in the formation of "ketone bodies" is

A) succinyl-CoA
B) methyl malonyl-CoA
C) propionyl-CoA
D) acetoacetyl-CoA

Question 39

The unsaturated fatty acids that are intermediates in the b-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

Question 40

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

Question 41

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.

Question 42

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.

Question 43

Which are the three most common ketone bodies?

A) Acetone, formaldehyde, acetoacetate.
B) Acetone, butyric acid and oxaloacetate.
C) Acetone, b-hydroxybutyrate and acetoacetate.
D) Acetone, b-hydroxybutyrate and oxaloacetate.
E) Acetocetate, b-hydroxybutyrate and oxaloacetate.

Question 44

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.

Question 45

Which group of small molecules best fit the boxes associated with the reaction shown?

A) I
B) II
C) III
D) IV

Question 46

The enzyme activity catalyzing the reaction shown is best termed a

A) reductase
B) ketothiolase
C) transferase
D) dehydratase

Question 47

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.

Question 48

Reduction reactions during fatty acid synthesis utilize

A) FADH₂.
B) NADH.
C) NADPH.
D) FADH₂ and NADH.
E) FADH₂ and NADPH.

Question 49

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

Question 50

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.

Question 51

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

Question 52

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

Question 53

The enzyme activity catalyzing the reaction shown is best termed a

A) reductase
B) ketothiolase
C) transferase
D) dehydratase

Question 54

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.

Question 55

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

Question 56

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

Question 57

Synthesis of fatty acids involves simple reversal of the b-oxidation cycle.

Question 58

"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.

Question 59

Acetyl-CoA carboxylase uses which of these cofactors?

A) thiamine pyrophosphate
B) Vitamin B₁₂
C) NAD
D) biotin

Question 60

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

Question 61

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

Question 62

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

Question 63

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

Question 64

Drugs are available to lower cholesterol which actually inhibit its synthesis in the body.

Question 65

The first true steroid synthesized in the steroid pathway is the following:

A) Cholesterol.
B) Squalene
C) Lanosterol
D) Progesterone
E) Mevalonic acid

Question 66

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.

Question 67

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.

Question 68

The ultimate precursor of all the carbon atoms in steroids is

A) acetyl-CoA (acetyl group)
B) oxaloacetate
C) succinyl-CoA (succinyl group)
D) a-ketoglutarate

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.

Question 70

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.

Question 71

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.

Question 72

The committed step in cholesterol biosynthesis is catalyzed by

A) HMG-CoA synthase
B) HMG-CoA reductase
C) mevalonate kinase
D) squalene monooxygenase

Question 73

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

Question 74

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.

Question 75

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

Question 76

Compared to b-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.

Question 77

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

Question 78

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

Question 79

Cholesterol is a precursor of all of the following except

A) cortisone
B) testosterone
C) progesterone
D) lanosterol

Question 80

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.