Deck 17: Lipid Metabolism I: Synthesis, Storage, and Utilization of Fatty Acids and Triacylglycerols

Question 1

The beta-oxidation of fatty acids

A) occurs in the mitochondrial matrix.
B) occurs in the cytosol.
C) produces only acetyl-CoA.
D) requires NADP in one of the steps.
E) occurs only in skeletal and heart muscle.

Answer 1

occurs in the mitochondrial matrix.

Question 2

During the biosynthesis of saturated fatty acids, the addition of every two-carbon unit requires

A) 2 NADH + 2 H+ + 1 ATP
B) 2 NADPH + 2 H+ + 1 ATP
C) 1 NADPH + H+ + 1 ATP
D) 1 NADH + H+ + 1 FADH2 + 1 ATP
E) 1 NADPH + H+ + 1 FADH2 + 1 ATP

Answer 2

2 NADPH + 2 H+ + 1 ATP

Question 3

Complete hydrogenation of linoleate produces

A) stearate.
B) palmitate.
C) oleate.
D) palmitoleate.
E) none of the above.

Answer 3

stearate.

Question 4

The fatty acid synthase complex contains all the following EXCEPT

A) a reductase.
B) a dehydratase.
C) a carboxylase.
D) a condensing enzyme.
E) a transacylase.

Question 5

Which of the following compounds will generate, upon oxidation, the highest yield of ATP on a mole per mole basis?

A) myristate (14:0)
B) myristoyl-CoA
C) 1,2-dimyristoylphosphatidylserine
D) 1,2,3-trimyristoylglycerol
E) cholesteryl myristate

Question 6

True statements about de novo fatty acid synthesis include

A) It utilizes acetyl CoA from carbohydrates and occurs in the liver and adipocyte inner mitochondrial matrix.
B) The rate limiting step involves a reaction in which acetyl CoA accepts a one carbon group from another acetyl CoA to form malonyl CoA.
C) Acetyl CoA carboxylase is active only in its multimeric form which contains biotin in a N-carboxybiotin-enzyme complex.
D) Fatty acid synthase is a complex enzyme in humans which is active as a homodimer. Each round of synthesis adds two carbons from malonyl-CoA to the methyl end of the fatty acid chain. The final product contains the original two carbons
E) The acyl carrier protein (ACP) in the fatty acid synthase enzyme contains a biotin moiety esterified to a hydroxyl group of serine to provide the sulfhydryl group onto which the growing fatty acid chain is always attached.

Question 7

The theoretical P/O ratio for the oxidation of a fatty acid to acetyl-CoA is

A) 3.0
B) 2.5
C) 2.0
D) 0.25
E) 0

Question 8

All of the following are directly involved in the conversion of fatty acids and glycerol to triglycerides EXCEPT

A) ATP.
B) A specific phosphatase.
C) NAD.
D) Phosphatidic acid.
E) Acyl-CoA's.

Question 9

A condition which favors increased ketone body synthesis is

A) increased glycogenolysis in skeletal muscle.
B) increased fatty acid synthesis in liver.
C) increased lipolysis in adipose tissue.
D) decreased gluconeogenesis in liver.

Question 10

The reductive steps in fatty acids synthesis are carried out by

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

Question 11

In contrast to fatty acids, which of the following is characteristic of ketone bodies?

A) carried by albumin in blood
B) soluble in water
C) require carnitine for transport into mitochondria
D) contain an average of 18 carbon atoms
E) may be saturated or unsaturated

Question 12

The major site of the formation and release of acetoacetate is

A) adipose tissue.
B) brain.
C) liver.
D) muscle.
E) small intestine.

Question 13

Mobilization of fat from adipose tissue requires the enzymatic activity of

A) lipoprotein lipase.
B) hormone-sensitive lipase.
C) phospholipase A2.
D) pancreatic lipase.
E) glycerol kinase.

Question 14

The beta-oxidation of oleic acid (delta-9) as opposed to palmitic acid requires the addition of which of the following enzymes?

A) enoyl-CoA hydratase
B) L-beta-ketoacyl-CoA thiolase
C) enoyl-CoA isomerase
D) acyl-CoA dehydrogenase
E) L-beta hydroxyacyl-CoA dehydrogenase

Question 15

Which of the following is true about polyunsaturated fatty acids found in man?

A) The first double bond is between carbons 2 and 3.
B) The double bonds are generally TRANS.
C) The double bonds are in a very stable conjugated system.
D) Generally, the double bonds are separated by one methylene group.

Question 16

A reaction for the synthesis of triacylglycerol believed to be unique in the intestine is

A) phosphatidic acid ---> diacylglycerol + Pi.
B) fatty acid + ATP + CoA ---> fatty acid-CoA + AMP + PPi.
C) diacylglycerol + fatty acyl-CoA ---> triacylglycerol + CoA.
D) monoacylglycerol + fatty acyl-CoA ---> diacylglycerol + CoA.
E) phosphatidylcholine + diacylglycerol ---> triacylglycerol + lysophosphatidylcholine.

Question 17

Fatty acid oxidation is a major source of energy in all of the following tissues EXCEPT

A) liver.
B) kidneys.
C) brain.
D) heart muscle.
E) resting skeletal muscle.

Question 18

The enzyme primarily responsible for generating acetyl-CoA in the cytoplasm is

A) ATP-citrate synthase.
B) malic enzyme.
C) malate dehydrogenase.
D) ATP-citrate lyase.
E) acetyl-CoA carnitine transferase.

Question 19

The predominant fatty acyl group in stored triglycerides is

A) arachidonate.
B) linoleate.
C) palmitate.
D) oleate.
E) stearate

Question 20

Which of the following molecules possesses a phosphopantetheine group?

A) Acetyl CoA
B) Acyl carrier protein
C) Both
D) Neither

Question 21

All of the following molecules are either substrates, cofactors or intermediates in the synthesis of triglyceride EXCEPT which one?

A) Glycerol 3-phosphate
B) Fatty acyl-CoA
C) Phosphatidic acid
D) CDP-diglyceride
E) water

Question 22

Oxidation of acetoacetic acid to carbon dioxide and water

A) by the liver mitochondria follows its direct reaction with CoA-SH.
B) requires an investment of two equivalents of ATP.
C) requires transfer to the CoA residue of succinyl-CoA.
D) takes place preferentially in the brain.
E) yields 38 equivalents of ATP.

Question 23

The β-oxidation of a 16 carbon fatty acyl CoA to 8 acetyl CoAs would generate:

A) 7 FADH2 and 7 NADH
B) 8 FADH2 and 8 NADH
C) 14 NADPH
D) 16 NADPH
E) 7 NADPH

Question 24

All of the following enzymes are involved in the beta-oxidation of palmitic acid EXCEPT

A) Enoyl-CoA hydratase
B) Acyl-CoA thiolase
C) 3 cis --> 2 trans enoyl-CoA isomerase
D) Acyl-CoA dehydrogenase
E) L-beta-hydroxyacyl-CoA dehydrogenase

Question 25

The function of fatty acyl-CoA dehydrogenase of beta-oxidation is most analogous to that of

A) beta-hydroxybutyrate dehydrogenase.
B) alpha-ketoglutarate dehydrogenase.
C) glutamate dehydrogenase.
D) succinate dehydrogenase.
E) NADH dehydrogenase.

Question 26

Each of the following processes occurs predominantly in mitochondria EXCEPT

A) cholesterol side-chain cleavage.
B) ketone body formation.
C) tricarboxylic acid cycle reactions.
D) fatty acid biosynthesis.
E) oxidative phosphorylation.

Question 27

The primary action of leptin is the

A) activation of triacylglycerol synthesis in adipose.
B) inhibition of insulin secretion from pancreatic beta cells.
C) modulation of polypeptide secretion from hypothalamus.
D) promotion of increase in skeletal muscle mass.
E) stimulation of ketone body utilization by brain.

Question 28

Citrate regulates fatty acid metabolism by

A) inhibiting delta9-desaturase.
B) inhibiting acyl-CoA synthetase.
C) inhibiting carnitine acyltransferase.
D) stimulating acetyl-CoA carboxylase.
E) stimulating fatty acid synthase.

Question 29

Lipids are the most efficient forms of biologically stored energy because they are

A) highly insoluble.
B) highly soluble.
C) highly oxidized.
D) highly reduced.
E) converted directly to ATP.

Question 30

The synthesis of fatty acids by the de novo pathway from acetyl-CoA

A) proceeds by the reversal of beta-oxidation.
B) occurs primarily in mitochondria.
C) requires NADPH, ATP and bicarbonate.
D) is increased during fasting.
E) utilizes acetoacetyl-CoA as substrate for beta-ketoacyl reductase.

Question 31

Carnitine is involved in all of the following processes EXCEPT

A) the transport of fatty acyl groups across the inner mitochondrial membrane.
B) formation of an ester bond with fatty acids.
C) maintenance of separate pools of coenzyme A in the mitochondrial matrix and the cytosol.
D) transport of citrate from mitochondria for synthesis of malonyl-CoA in the cytosol.
E) use of fatty acids released from adipose tissue for generation of energy in other tissues.

Question 32

All of the compounds listed below are ketone bodies EXCEPT which one?

A) acetoacetate.
B) beta-hydroxybutyrate.
C) alpha-ketoglutarate.
D) acetone.
E) All of the above are ketone bodies.

Question 33

De novo fatty acid biosynthesis occurs in the

A) mitochondria.
B) endoplasmic reticulum (microsomal fraction).
C) lysosomes.
D) cytosol.
E) nucleus.

Question 34

An intermediate produced during the oxidation of palmitic acid to carbon dioxide and water in skeletal muscle mitochondria is

A) pyruvic acid.
B) malonyl-CoA.
C) hydroxymethyl-glutaryl-CoA
D) acetoacetyl-CoA.
E) propionyl-CoA.

Question 35

Acetyl-CoA for de novo fatty acid biosynthesis is formed by the energy-dependent cleavage of

A) pyruvate
B) oxaloacetate
C) citrate
D) alpha-ketoglutarate
E) acetoacetate

Question 36

The most immediate impact of malonyl CoA inhibition of carnitine: fatty acyl CoA transferase is to

A) stimulate the synthesis of ketone bodies.
B) Stimulate fatty acid oxidation leading to a decreased rate of gluconeogenesis.
C) stimulate fatty acid oxidation leading to a decreased rate of gluconeogenesis.
D) turn back fatty acids heading for the mitochondrion while stimulating fatty acid elongation in the endoplasmic reticulum.
E) increase the concentration of mitochondrial acetyl CoA available for combustion through the TCA cycle.

Question 37

Enzymes for the synthesis of oleic acid from palmitic acid are located in the

A) cytosol.
B) endoplasmic reticulum.
C) mitochondria.
D) lysosomes.
E) Golgi apparatus.

Question 38

How may of the carbon atoms from stearic acid may contribute, through cellular metabolism, to the net synthesis of glucose?

A) 18
B) 17
C) 6
D) 3
E) 0

Question 39

All of the following are intermediates or enzymes in the production of triglycerides in a cell of fatty tissue from a lipoprotein of blood plasma EXCEPT which one?

A) Hormone sensitive lipase
B) Free fatty acids
C) Phosphatidic acid
D) A diglyceride
E) Fatty acyl-CoA transferase

Question 40

Glucose metabolism is necessary in adipose tissue to supply which of the following for the formation of triglycerides?

A) ribose 5-phosphate
B) succinyl-CoA
C) alpha-glycerol phosphate
D) phosphoenolpyruvate

Question 41

Which of the following is a property of the triacylglycerols?

A) Their specific gravity is higher than that of water.
B) They are resistant to attack by alkali.
C) Those occurring naturally with an asymmetric carbon atom are by convention named as if they derive from L-glyceraldehyde.
D) They are solid at body temperature.

Question 42

Which of the following statements regarding the fatty acid elongation system located in the endoplasmic reticulum is CORRECT?

A) This system utilizes only NADH as a source of reducing equivalents.
B) This system utilizes both NADH and NADPH as sources of reducing equivalents.
C) This system utilizes only NADPH as a source of reducing equivalents.
D) This system only elongates saturated long chain fatty acyl-CoA derivatives.
E) Acetyl-CoA is the source of the two-carbon unit that is added to the carboxyl end of the fatty acid being elongated.

Question 43

Which one of the following is an example of precursor (feedforward) activation? The effect of

A) palmityl CoA on acetyl CoA carboxylase.
B) citrate on acetyl CoA carboxylase.
C) insulin on hormone-sensitive lipase.
D) malonyl CoA on carnitine acyl transferase I.

Question 44

In man the synthesis of fatty acids from glucose proceeds primarily in the

A) adipose tissue.
B) intestines.
C) kidney.
D) liver.
E) skeletal muscles

Question 45

Export of acetyl-CoA from mitochondria to cytosol to participate in fatty acid or steroid biosynthesis involves

A) a specific carrier for acetyl-CoA in the mitochondrial membrane.
B) transport of citrate from mitochondria.
C) synthesis of acetoacetate from acetyl-CoA in mitochondria.
D) transport of oxaloacetate from mitochondria.
E) formation of acetyl-carnitine.

Question 46

Functional mammalian fatty acid synthase is composed of:

A) A dimer of identical subunits, with each subunit catalytically functioning independently
B) A dimer of identical subunits, with the subunits forming two catalytically active sites in the region where the subunits interface.
C) Both
D) Neither

Question 47

The coenzyme involved in the synthesis of malonyl-CoA from acetyl-CoA is

A) thiamine.
B) biotin.
C) nicotinamide.
D) riboflavin.
E) folic acid.

Question 48

Carnitine acyltransferase catalyzes the

A) transfer of a fatty acyl group from the sulfhydryl group of fatty acyl-CoA to the carboxyl group of carnitine.
B) energy-dependent carboxylation of carnityl-CoA.
C) transfer of a fatty acyl group from the sulfhydryl group of fatty acyl-CoA to the secondary hydroxyl group of carnitine.
D) energy dependent formation of a thioester bond between the carboxyl group of a fatty acid and the sulfhydryl group of acyl carrier protein.
E) transfer of a fatty acyl group from the sulfhydryl group of fatty acyl-CoA to the sulfhydryl group of carnitine.

Question 49

Elongation of an acyl-CoA derivative in mitochondria requires

A) NADH + H+ and acetyl-CoA.
B) NADH + H+ and malonyl-CoA.
C) NADPH + H+ and acetyl-CoA.
D) NADPH + H+ and malonyl-CoA.
E) NADPH + H+, malonyl-CoA and ATP.

Question 50

The correct structure for palmitic acid is

A) CH3(CH2)12 COOH
B) CH3(CH2)14 COOH
C) CH3(CH2)16 COOH
D) CH3(CH2)18 COOH
E) None of the other answers is correct.

Question 51

Fatty acid synthesis

A) uses NADH as the source of reducing equivalents.
B) occurs in the mitochondria of the cell.
C) requires the intermediate synthesis of HMG-CoA to begin the process.
D) requires that the growing hydrocarbon chain be attached to acyl carrier protein.
E) is the main use of energy and reducing equivalents provided by glycolysis in red blood cells.

Question 52

All of the following are involved in processes related to fatty acid synthesis EXCEPT which one?

A) biotin
B) ATP
C) NADH
D) Pantothenate
E) Carbon Dioxide

Question 53

ATP is required for fatty acid oxidation for the reaction catalyzed by

A) acyl-CoA dehydrogenase.
B) acyl-CoA synthetase.
C) thiolytic cleavage.
D) carnitine acyltransferase.

Question 54

With respect to the complete oxidation of fatty acids, as the degree of unsaturation increases the yield of ATP

A) is constant.
B) slightly decreases.
C) slightly increases.
D) reaches a maximum with three double bonds.
E) depends upon the tissue.

Question 55

Among the differences between fatty acid synthesis and fatty acid oxidation is the fact that

A) synthesis occurs in the mitochondria and oxidation in cytosol.
B) synthesis uses NADH and oxidation uses FAD.
C) synthesis is accelerated and oxidation depressed in diabetes.
D) malonyl-CoA is an intermediate in oxidation, but not in synthesis.
E) the acyl groups form different thioesters in synthesis and oxidation.

Question 56

Which of the following is the best positive effector of acetyl coenzyme A carboxylase?

A) citrate
B) oxaloacetate
C) malonyl coenzyme A
D) ADP
E) pyruvate

Question 57

Which of the following is the most active positive effector of acetyl-CoA carboxylase?

A) citrate
B) oxaloacetate
C) malonyl-CoA
D) ADP
E) pyruvate

Question 58

Which of the following provides reducing equivalents for the formation of NADPH in the cytoplasm?

A) malonyl-CoA
B) succinyl-CoA
C) phosphatidic acid
D) acetoacetic acid
E) malic acid

Question 59

All of the following fatty acids are synthesized in man EXCEPT

A) oleic acid.
B) linoleic acid.
C) palmitoleic acid.
D) stearic acid.
E) palmitic acid.

Question 60

The sequence of reactions for the beta-oxidation of fatty acids is

A) activation, dehydrogenation, hydration, dehydrogenation and cleavage.
B) activation, hydrogenation, dehydrogenation and cleavage.
C) activation, oxidation, dehydrogenation, hydration and cleavage.
D) activation, dehydrogenation, hydration and cleavage.
E) activation, hydrogenation, hydration, hydrogenation and cleavage.

Question 61

The biosynthesis of triacylglycerols in adipose requires

A) decreased activation of long?chain fatty acids.
B) decreased levels of plasma leptin.
C) increased glycerol secretion from adipose.
D) increased glucose uptake by adipose.
E) increased levels of plasma glucagon.

Question 62

Position number one in the triglycerides of man is filled by a fatty acid residue that is

A) always saturated.
B) usually saturated.
C) always unsaturated.
D) usually unsaturated.
E) equally likely to be saturated or unsaturated.

Question 63

The rate-limiting step of fatty acid synthesis is catalyzed by

A) pyruvate dehydrogenase.
B) citrate-cleavage enzyme.
C) malic enzyme.
D) acetyl-CoA carboxylase.
E) thiolase.

Question 64

Which of the following is an 18 carbon fatty acid with 3 double bonds?

A) palmitic acid
B) oleic acid
C) linoleic acid
D) linolenic acid
E) arachidonic acid

Question 65

How may of the carbon atoms from stearic acid may contribute, through cellular metabolism, to the net synthesis of glucose?

A) 18
B) 17
C) 6
D) 3
E) 0

Question 66

What is the rate limiting step in the conversion of triglyceride to free fatty acids in adipose tissue?

A) The formation of Cyclic AMP.
B) The diffusion of glycerol into the blood.
C) Hydrolysis by the hormone stimulated lipase.
D) Stimulation of lipoprotein lipase.
E) None of the above.

Question 67

Two vitamins important in beta-oxidation are

A) riboflavin and niacin.
B) pantothenic acid and cholecalciferol.
C) coenzyme A and thiamine.
D) riboflavin and ascorbic acid.

Question 68

In mitochondria, the electron donor for the last reductive step in the elongation of the carbon chain of a fatty acid is

A) NADH.
B) FADH2.
C) FMNH2.
D) NADPH.
E) coenzyme Q-2H.

Question 69

Lipolysis:

A) is stimulated by insulin.
B) is inhibited by glucagon.
C) requires the action of hormone-sensitive lipase.
D) requires an apolipoprotein.
E) results in an increase in blood concentrations of esterified fatty acids.

Question 70

A deficiency of carnitine would be expected to interfere with which of the following?

A) Beta oxidation of long chain fatty acids.
B) Transport of fatty acids into adipose cells.
C) The synthesis of palmitate.
D) Mobilization of stored triacylglycerols from adipose tissue.
E) oxidation of ethanol to acetic acid.

Question 71

In liver, acetoacetate may be preferentially

A) reduced to beta-hydroxybutyrate.
B) esterified to coenzyme A.
C) oxidized to 2 moles of acetate.
D) none of the above.

Question 72

The steps of beta-oxidation parallel portions of:

A) Gluconeogenesis
B) Glycolysis
C) Krebs cycle
D) Oxidative phosphorylation
E) Pentose phosphate shunt

Question 73

What is the maximum percentage of carbon atoms of glucose that can be used for synthesis of palmitic acid?

A) 100%
B) 75%
C) 66-2/3%
D) 50%
E) 33-1/3%

Question 74

A deficiency in carnitine will result in

A) a decreased synthesis of phospholipids in the endoplasmic reticulum.
B) a decreased level of fatty acyl CoA in the cytoplasm.
C) a decreased synthesis of fatty acyl adenylate in the mitochondria.
D) an increased level of fatty acid in the cytoplasm.
E) an increased level of fatty acyl pantetheine in the mitochondria.

Question 75

In order for acetoacetate to be utilized by extrahepatic tissues, which of the following reactions must occur?

A) decarboxylation of acetoacetate to form acetone
B) carboxylation of acetoacetate
C) reduction to beta-hydroxybutyrate
D) transfer of a coenzyme A from succinyl CoA to form acetoacetyl CoA
E) condensation with acetyl CoA to form HMG CoA

Question 76

Fatty acids with an odd number of carbon atoms and certain branched-chain fatty acids can support the net synthesis of glucose because they

A) increase the NAD/NADH ratio.
B) can produce methylmalonyl-CoA which is converted to succinyl-CoA.
C) are converted to malonyl-CoA.
D) yield NADPH on oxidation.
E) are converted to acetoacetate and beta-hydroxybutyrate.

Question 77

When fatty acid biosynthesis is stimulated, beta-oxidation of fatty acids is inhibited. This inhibition occurs mainly because

A) the pool of acetyl-CoA is depleted by the TCA cycle and fatty acid biosynthesis.
B) malonyl-CoA inhibits carnitine acyltransferase I.
C) high levels of ATP inhibit phosphofructokinase.
D) high levels of citrate stimulate acetyl-CoA synthase.
E) none of the above.

Question 78

The formation of acetoacetic acid from acetyl-CoA involves which of the following compounds as an intermediate?

A) malonic acid
B) mevalonic acid
C) 3-hydroxy-3-methylglutaryl-CoA
D) 3-hydroxybutyryl-CoA
E) succinyl-CoA

Question 79

What is the main function of beta-oxidation?

A) production of carbon dioxide.
B) provides NADPH.
C) degradation of fatty acids.
D) the main source of odd chain fatty acids.
E) important in membrane structure.

Question 80

The oxidation and degradation of fatty acids in the cell

A) begins with the fatty acid thioester of CoA.
B) does not produce useful energy for the cell.
C) is inhibited by carnitine.
D) occurs primarily in the nucleus.
E) proceeds through successive shortening of the fatty acids by three-carbon units.