Deck 16: Lipid Metabolism

Question 1

The hydration step in the synthesis of acyl-ACP for fatty acid elongation forms the ________ isomers of the beta-hydroxy intermediate while the ________ isomers are formed during fatty acid degradation.

A)L,L
B)L,D
C)D,L
D)D,D

Answer 1

D,L

Question 2

Eicosanoids are not like hormones in that they

A)can alter blood flow.
B)act in the area where they are formed.
C)can mediate inflammation and swelling.
D)are chemically diverse.

Answer 2

act in the area where they are formed.

Question 3

Fatty acid synthesis is different in bacteria than in eukaryotic cells because ________.

A)bacteria do not form malonyl CoA
B)eukaryotes use acetyl CoA to form malonyl CoA
C)bacteria do not form acetyl ACP
D)bacteria do not form acetoacetyl CoA

Answer 3

bacteria do not form acetyl ACP

Question 4

Which of the following is true for carboxylation of acetyl CoA?

A)In animals and yeast,it requires three separate protein subunits.
B)It is a metabolically reversible reaction.
C)In bacteria,it is catalyzed by a bifunctional enzyme.
D)The regulatory enzyme is acetyl-CoA carboxylase.

Question 5

What type of reactions occur to convert glycerol-3-phosphate to phosphatidate?

A)Esterification.
B)Dephosphorylation.
C)Phosphorylation.
D)Decarboxylation.
E)Hemiacetal formation.

Question 6

Phosphatidate is synthesized from glycerol-3-phosphate.Which statement is correct about the enzymes and the order of esterification reactions in the synthesis?

A)Esterification at C-2 by 1-acylglycerol-3-phosphate acyltransferase followed by esterification at C-1 by glycerol-3-phosphate acyltransferase.
B)Esterification at C-1 by 1-acylglycerol-3-phosphate acyltransferase followed by esterification at C-2 by glycerol-3-phosphate acyltransferase.
C)Esterification at C-2 by glycerol-3-phosphate acyltransferase followed by esterification at C-1 by 1-acylglycerol-3-phosphate acyltransferase.
D)Esterification at C-1 by glycerol-3-phosphate acyltransferase followed by esterification at C-2 by 1-acylglycerol-3-phosphate acyltransferase.

Question 7

Before free fatty acids can be incorporated into lipids,they must be activated to

A)eicosanoids.
B)thioesters of Coenzyme A.
C)acyl carrier protein (ACP).
D)NADPH.

Question 8

Which of the following is a true statement for fatty acid synthesis?

A)It occurs in the mitochondria.
B)The reducing power for synthesis is supplied by NAD+ and ubiquinone.
C)Both A and B.
D)None of the above.

Question 9

The elongation of fatty acids is a repetition of three reactions adding carbons from ________ after each cycle until completion.

A)malonyl CoA
B)malonyl ACP
C)acetyl CoA
D)acetyl ACP

Question 10

The role of biotin in fatty acid biosynthesis is in

A)elongation.
B)malonyl CoA formation.
C)initiation.
D)ATP activation.

Question 11

The first step in fatty acid synthesis is the formation of ________ from acetyl CoA and carbon dioxide.

A)acetyl ACP
B)acetoacetyl ACP
C)malonyl CoA
D)acetoacetyl CoA

Question 12

Why are triacylglycerols able to provide more energy than carbohydrates (gram for gram)?

A)The triacylglycerols have an extremely high group transfer potential.
B)The carbohydrates are already in a more oxidized state than the triacylglycerols.
C)The carbohydrates contain fewer carbon-carbon bonds.
D)The triacylglycerols are less soluble in water than the carbohydrates.

Question 13

Phosphatidate is an intermediate in the synthesis of ________.

A)triacylglycerols and glycerophospholipids
B)glycerophospholipids only
C)sphingolipids
D)cholesterol

Question 14

Which of the following is not a stage of fatty acid synthesis?

A)Condensation of precursors.
B)Rearrangement.
C)Reduction.
D)Dehydration.

Question 15

The reaction,Palmitoyl-ACP→Palmitate + HS-ACP proceeds via which of the following enzymes?

A)Thioesterase.
B)Ketoacyl-ACP synthase.
C)Transacylase.
D)None of the above.

Question 16

Linoleate is an essential fatty acid in mammalian diets because mammalian cells ________.

A)synthesize it from arachidonate
B)do not use this acid for biosynthesis
C)can use it to synthesize eicosanoids
D)do not have a desaturase that acts beyond the carbon-9 position

Question 17

The cyclooxygenase-hydroperoxidase pathway is a precursor for each of the following except

A)thromboxane A2.
B)prostacyclin.
C)prostaglandins.
D)epinephrine.

Question 18

Which of the following is the regulated step of fatty acid synthesis in eukaryotes?

A)Carboxylation of acetyl CoA.
B)Transportation of mitochondrial acetyl CoA into the cytosol.
C)Assembly of the fatty acid chain.
D)All of the above.

Question 19

The intermediate 1,2-diacylglycerol can lead to the synthesis of all but which substance below?

A)Phosphatidylcholine.
B)Phosphatidylethanolamine.
C)Triacylglycerol.
D)Cholinesterase.

Question 20

To prepare for elongation reactions of fatty acid synthesis,the "3-keto" group must be reduced to the ________ form by transfer of electrons (and protons)to the 3-carbon position.

A)keto
B)methylene then hydroxyl
C)hydroxyl then methylene
D)all of the above

Question 21

How many cycles of β-oxidation are required to completely process a saturated C18 fatty acid?

A)6
B)8
C)9
D)18

Question 22

Lysosomal storage diseases occur when mutations cause defects in ________.

A)sphingolipid biosynthesis enzymes
B)sphingolipid degradation enzymes
C)lysosome formation
D)formation of N-acetylgalactosamine derivatives

Question 23

Which enzyme is needed for the oxidation of odd-chain saturated fatty acids that is not needed for even-chain fatty acids?

A)Methylmalonyl-CoA mutase.
B)Propionyl-CoA carboxylase.
C)Methylmalonyl-CoA racemase.
D)All of the above.

Question 24

Drugs called statins lower cholesterol levels because they ________.

A)degrade HMG-CoA reductase
B)bind serum cholesterol
C)inhibit HMG-CoA reductase
D)bind bile salts

Question 25

There are two forms of COX activity.COX-1 regulates stomach mucin,protecting the stomach lining;COX-2 promotes inflammation,pain and fever.Newer anti-inflammatory drugs for arthritic patients would inhibit

A)COX-1.
B)COX-2.
C)Both COX-1 and COX-2.
D)Arachidonate synthesis.

Question 26

Properties of aspirin may include

A)inhibition of COX activity.
B)increased production of prostaglandins.
C)Both A and B.
D)None of the above.

Question 27

There are four steps in the β-oxidation pathway.Some reaction types are listed below.Give the proper reaction types in the order that they occur in the β-oxidation pathway.
1. condensation
2. oxidation
3. reduction
4. thiolysis
5. hydration
6. phosphorylation
7. rearrangement

A)1,7,2,2
B)6,3,4,2
C)1,2,3,5
D)2,5,2,4

Question 28

What structure is shown below and what is its main function?

A)Coenzyme A;activation of fatty acids before β-oxidation.
B)Carnitine;transport of fatty acyl CoA into the mitochondrial matrix.
C)Taurocholate;one of the bile salts.
D)Acetoacetate;synthesis of fatty acids.

Question 29

Which sphingolipid is a precursor for all other types of sphingolipids?

A)Sphingomyelin.
B)Cerebroside.
C)Ganglioside.
D)Ceramide.

Question 30

Which lipid form is transported across the inner mitochondrial membrane before β-oxidation?

A)Acylcarnitine.
B)Fatty acyl CoA.
C)Acetoacetyl CoA.
D)Lysophospholipid CoA.

Question 31

All of the following occur during synthesis of ether lipids except

A)esterification of an acyl group from fatty acyl CoA to dihydroxyacetone phosphate.
B)displacement of the fatty acid of 1-acyldihydroxyacetone phosphate by a fatty alcohol.
C)oxidation of the keto group of 1-acyldihydroxyacetone by NADPH.
D)esterification of 1-alkylglycero-3-phosphate to produce 1-alkyl-2-acylglycero-3-phosphate.

Question 32

Isopentenyl pyrophosphate is the precursor for which of the following?

A)Terpenes.
B)Vitamin K.
C)Quinones.
D)All of the above.
E)None of the above.

Question 33

Cholesterol is a precursor for each of the following,except

A)bile salts.
B)vitamin D.
C)testosterone.
D)vitamin C.

Question 34

The pathway describing the formation of ether lipids in mammals begins with

A)the citric acid cycle.
B)pyruvic acid.
C)dihydroxyacetone phosphate.
D)choline.

Question 35

Which of the following is mismatched?

A)Bile salts - intestinal absorption of lipids.
B)B-estradiol - sex characteristics.
C)Cholesterol - membrane fluidity.
D)Squalene - lipid vitamin.

Question 36

A trifunctional enzyme for β-oxidation containing sites for activities for an entire pathway is an example of

A)cooperative control.
B)metabolic channeling.
C)energy loss.
D)separation of biosynthetic and degradation pathways.

Question 37

Fatty acids are oxidized in the ________.

A)mitochondrial matrix
B)cytosol
C)endoplasmic reticulum
D)mitochondrial inner membrane space

Question 38

Which of the following is a true statement for fatty acid oxidation?

A)It occurs in the cytosol.
B)Oxidation requires a three carbon substrate,which transfers a two-carbon unit to the chain.
C)Both NADH and QH₂ are produced.
D)None of the above.

Question 39

Which of the following is a true statement,concerning HMG-CoA reductase?

A)It is regulated by covalent modification of a serine in its active site.
B)It catalyzes the first committed step in cholesterol biosynthesis.
C)It causes the production of NADPH.
D)The product of the reaction it catalyzes is acetoacetyl CoA.

Question 40

If the carbonyl carbon of a fatty acyl CoA molecule with a C10 chain is labeled with 14C,how many rounds of β-oxidation are required to produce a radioactively labeled acetyl CoA?

A)One
B)Two
C)Four
D)Five

Question 41

During the fed state,which of the following occur(s)?

A)Insulin inhibition of the hydrolysis of stored triacylglycerols.
B)Insulin stimulation of malonyl CoA formation.
C)Allosteric inhibition of carnitine acyltransferase I.
D)All of the above.

Question 42

Why is it undesirable to have high concentrations of free fatty acids in cells?

A)They are unstable,free radicals that can react to form toxic substances.
B)They polymerize easily and can cause the cytosol to become too gel-like.
C)They are amphipathic and act as detergents that can degrade membranes.
D)They inhibit the uptake of pyruvate by mitochondria.

Question 43

What is the main function of the carnitine shuttle system?

A)To transport fatty acids into the mitochondrion.
B)To transport newly synthesized sphingolipids to the blood.
C)To carry cholesterol from its site of synthesis in the endoplasmic reticulum to the plasma membrane.
D)To aid in the assembly of chylomicrons.

Question 44

The conversion of the fatty acid palmitate (C16)to carbon dioxide via β-oxidation,the citric acid cycle and oxidative phosphorylation yield approximately ________ ATP equivalents.

A)3
B)32
C)106
D)800

Question 45

Each of the following is a principle hormonal regulator of fatty acid metabolism,except

A)bile salts.
B)glucagon.
C)insulin.
D)epinephrine.

Question 46

Which enzyme requires adenosylcobalamin as a cofactor?

A)Carnitine acyl transferase I.
B)Methylmalonyl-CoA mutase.
C)Enoyl-CoA hydratase.
D)Propionyl-CoA carboxylase.

Question 47

The main function of the bile salts is to ________.

A)transport lipids to the intestinal wall
B)act as counterions for the ionized forms of lipids
C)cleave the ester bonds in triacylglycerols to release free fatty acids
D)form the surface layer of chylomicrons

Question 48

Which dietary lipid usually contains no ester bonds?

A)Cholesterol.
B)Triacylglycerides.
C)Glycerophospholipidsh
D)None of the above,all dietary lipids are esterified.

Question 49

To oxidize the fatty acid molecule shown below,what enzyme(s)is(are)needed in addition to the enzymes needed for β-oxidation?

A)Enoyl-CoA isomerase only.
B)2,4-dienoyl-CoA reductase only.
C)Both enoyl-CoA isomerase and 2,4-dienoyl-CoA reductase.
D)No additional enzymes are needed besides the normal ones for β-oxidation.

Question 50

Regulation of acetyl CoA-carboxylase is accomplished by

A)inhibition by fatty acyl CoA.
B)activation by citrate (in vitro).
C)inactivation by high levels of glucagon.
D)All of the above.

Question 51

What is the fate of most glycerol that is released during the hydrolysis of triacylglycerols from adipocytes?

A)It is transported to the kidneys and excreted in the urine.
B)It is used in the synthesis of sphingolipids.
C)It is converted to glucose via gluconeogenesis in the liver.
D)It is absorbed by the chylomicrons.

Question 52

What is the major role of phospholipase A2?

A)To cleave the phosphate group from phospholipids.
B)To phosphorylate the enzyme enoyl-CoA.
C)To hydrolyze an ester bond in glycerophospholipids to form lysophosphoglyceride.
D)To transport glycerophospholipids in the blood.

Question 53

How many QH₂ and NADH are produced from a saturated fatty acid by one round of the β-oxidation pathway?

A)1 each.
B)1 QH₂ and 2 NADH.
C)2 each.
D)2 QH₂ and 1 NADH.

Question 54

Why is poor plasmalogen synthesis potentially fatal?

A)The nervous system is affected because plasmalogens are important constituents of the myelin sheath.
B)The mitochondria will not function properly due to lack of plasmalogen produced cardiolipin.
C)Poor nutrient absorption will occur in the small intestine where plasmalogens aid with the absorption of lipid-soluble vitamins and other hydrophobic substances.
D)Protein synthesis is affected due to the inability of plasmalogens binding ribosomes to the endoplasmic reticulum.

Question 55

To oxidize the fatty acid molecule shown below,what enzyme(s)is(are)needed in addition to the enzymes needed for β-oxidation?

A)Enoyl-CoA isomerase only.
B)2,4-dienoyl-CoA reductase only.
C)Both enoyl-CoA isomerase and 2,4-dienoyl-CoA reductase.
D)No additional enzymes are needed besides the normal ones for β-oxidation.

Question 56

Elevated levels of the hormone ________ stimulate the conversion of triacylglycerols stored in adipose cells to free fatty acids and monoacylglycerols to provide energy when carbohydrate stores are depleted.

A)insulin
B)glucagon
C)epinephrine
D)ergosterol

Question 57

Phosphatidylcholine synthesis occurs in the ________.

A)endoplasmic reticulum of eukaryotic cells
B)Golgi apparatus
C)mitochondrion
D)plasma membrane

Question 58

The structure shown below is ________.

A)taurocholate
B)glycerophospholipid
C)carnitine
D)lysophosphoglyceride

Question 59

Which bonds of the triacylglycerol shown are hydrolyzed by pancreatic lipase?

A)The carbon-carbon bonds between atoms 1,2 and 3.
B)The ester bond at carbon 2 only.
C)The bonds between the carbonyl carbons 4 and 6 and the first carbon of the hydrocarbon chains.
D)The ester bonds at carbons 1 and 3 only.

Question 60

Which statement is false about polyunsaturated fatty acids?

A)They have both odd-numbered and even-numbered double bonds.
B)Their synthesis is more energy-efficient than the synthesis of saturated fatty acids.
C)Some double bonds are rearranged during their degradation.
D)They require D3,D2-enoyl-CoA isomerase for their oxidation.

Question 61

Which is not a ketone body?

A)Dihydroxyacetone.
B)Acetoacetate.
C)Acetone.
D)β-hydroxybutyrate.

Question 62

Double bonds positioned farther than nine carbons from the carboxyl end of fatty acids occur only in vertebrates.

Question 63

In adult mammals fatty acid synthesis largely occurs in the cytosol of liver cells and adipocytes.

Question 64

In mammals the oxidation of fatty acids produces a two-carbon product and the synthesis of fatty acids begins with a two-carbon substrate.

Question 65

CoA derivatives are the active thioesters in fatty acid oxidation.

Question 66

The largest lipoproteins are the ________.

A)chylomicrons
B)VLDLs
C)LDLs
D)HDLs

Question 67

In eukaryotes the enzyme complex called fatty acid synthase is responsible for the assembly of the fatty acid chain.

Question 68

The long chain fatty acid arachidonate is the precursor for many eicosanoids.

Question 69

Eicosanoids,like hormones,are transferred through the blood stream to areas targeted for activities such as vasoconstriction,sensitivity,inflammation and swelling.

Question 70

Which do you expect to have the highest protein content by percent?

A)VLDLs.
B)ILDs.
C)HDLs.
D)All of the lipids above have about the same protein content.

Question 71

Linoleate is required for human diet because it is necessary for the synthesis of arachidonate and eicosanoids.

Question 72

While mutation of genes for the biosynthesis of sphingolipids are probably lethal,mutations in genes for the degradation of sphingolipids often lead to metabolic diseases such as Tay-Sachs disease.

Question 73

Animals use a type I fatty acid synthesis system (FAS
I)while bacteria use a type II fatty acid synthesis system (FAS II).

Question 74

The enzyme for β-oxidation is trifunctional with a2b2 tertiary structure.

Question 75

A biotin-dependent enzyme is responsible for catalyzing the carboxylation of acetyl CoA.

Question 76

Ketone bodies are synthsized in the ________ from ________.

A)mitochondria;oxaloacetate
B)liver;oxaloacetate
C)mitochondria;acetyl CoA
D)liver;acetyl CoA

Question 77

A patient is found to have a high concentration of cholesterol in the blood and deposits of cholesterol under the skin.The patient is diagnosed with familial hypercholesterolemia.What is the likely cause of this condition?

A)A deficiency in insulin production by the pancreas.
B)Insufficient chylomicron concentration in the blood.
C)Overproduction of lysosomal lipases.
D)Lack of LDL receptors on the surfaces of nonhepatic cells.

Question 78

Ketone bodies may be produced during periods of starvation.Which statement is true about ketone bodies?

A)They are toxic by-products from the degradation of muscle tissue.
B)They serve as substitutes for glucose to fuel the brain.
C)They are used to replenish oxaloacetate in the citric acid cycle.
D)The reduction of ketone bodies keeps the electron transport chain going.

Question 79

Triacylglycerols are more efficient to store than carbohydrates because their hydrophobicity allows them to be stored in adipose cells without large amounts of bound water molecules.

Question 80

S-adenosylmethionine methylates phosphatidylethanolamine to form phosphatidylcholine.