Deck 16: Lipid Metabolism

Question 1

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 1

act in the area where they are formed.

Question 2

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 2

bacteria do not form acetyl ACP

Question 3

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

Answer 3

inhibit HMG-CoA reductase

Question 4

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

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

Question 5

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 6

Phosphatidate is an intermediate in the synthesis of .

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

Question 7

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 8

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 9

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 10

Cholesterol is a precursor for each of the following, except

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

Question 11

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 12

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 13

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 14

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 15

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

A) condensation of precursors
B) rearrangement
C) reduction
D) dehydration

Question 16

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 17

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 18

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 19

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

A) sphingomyelin
B) cerebroside
C) ganglioside
D) ceramide

Question 20

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 21

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 22

To oxidize the fatty acid molecule shown below, what enzymes) 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 23

Fatty acids are oxidized in the .

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

Question 24

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 25

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 26

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 27

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 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

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 30

Phosphatidylcholine synthesis occurs in the .

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

Question 31

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 32

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 33

How many QH₂ and NADH are produced 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 34

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 35

To oxidize the fatty acid molecule shown below, what enzymes) isare) 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 36

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 37

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 38

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 39

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 40

Which of the following is mis-matched?

A) bile salts - intestinal absorption of lipids
B) b-estradiol - sex characteristics
C) cholesterol - membrane fluidity
D) squalene - lipid vitamin

Question 41

Which of the following does do) not occur during the fasting state?

A) increased insulin levels
B) inhibition of lipolysis
C) an increase in the concentration of albumin-bound fatty acids in the blood
D) A and B only
E) All of the above

Question 42

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

Question 43

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 44

The structure shown below is .

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

Question 45

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 46

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

A) glucagon.
B) adrenaline.
C) insulin.
D) epinephrine.

Question 47

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

Question 48

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

Question 49

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 glycagon.
D) All of the above

Question 50

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 51

Which is not a ketone body?

A) dihydroxyacetone
B) acetoacetate
C) acetone
D) β-hydroxybutyrate

Question 52

Non-insulin-dependent diabetes mellitus NIDDM) is characterized by .

A) insulin secretion that is always at levels well below normal
B) insufficient insulin levels initiated during gestational diabetes
C) a shortage of insulin receptors that leads to accumulation of blood glucose
D) an inherited genetic abnormality in the insulin gene that yields a much less active insulin

Question 53

The largest lipoproteins are the .

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

Question 54

During the fed state, which of the following occurs)?

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 55

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 56

Which dietary lipid usually contains no ester bonds?

A) cholesterol
B) triacylglycerides
C) glycerophospholipids
D) None of the above, all dietary lipids are esterified

Question 57

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 58

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 59

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 60

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 61

High levels of VLDLs have been found to have a protective effect against atherosclerosis.

Question 62

Ketone bodies are normally broken down in the liver in preparation for excretion.

Question 63

Most of the lipids in the diets of mammals are free fatty acids.

Question 64

An increase in glucagon levels activates the enzyme which catalyzes malonyl CoA synthesis in the liver.

Question 65

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 66

Chylomicrons are found in high concentrations in the blood only during fasting when lipids from adipose tissue are mobilized.

Question 67

CoA derivatives are the active thioesters in fatty acid oxidation.

Question 68

Cytosolic HMG-CoA is used for ketone body synthesis.

Question 69

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

Question 70

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

Question 71

Snake venom can cause the lysis of red blood cells due to the presence of phospholipase A₂.

Question 72

During starvation ketone bodies can take the place of glucose as a fuel for brain cells.

Question 73

S-adenosylmethionine methylates phosphatidylethanolamine to form phosphatidylcholine.

Question 74

The bile salts taurocholate and glycocholate are amphipathic derivatives of cholesterol.

Question 75

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