Deck 23: Fatty Acid Catabolism

Question 1

Bile salts are important in the initial digestion of triacylglycerols in the intestine because they:

A) are coenzymes for pancreatic lipase.
B) convert the inactive lipase into the active form.
C) emulsify the triacylglycerol globules to produce greater surface area which will increase the activity of the lipase.
D) activate the cleavage at the C-2 position.
E) permit greater permeability of the triacylglycerols through the intestinal membrane.

Answer 1

C

Question 2

Where in the cell are fatty acids condensed with coenzyme A to form acyl-CoA for β-oxidation?

A) mitochondrial matrix
B) cytoplasm
C) outer mitochondrial membrane
D) inner mitochondrial membrane
E) none of the above

Answer 2

C

Question 3

How many NAD⁺ are reduced in the β-oxidation of stearoyl-CoA to form nine molecules of acetyl-CoA?

A) 18
B) 16
C) 12
D) 9
E) 8

Answer 3

E

Question 4

The majority of lipid digestion occurs in the duodenum by the enzyme ____ that produces ____ and ____ for absorption.

A) acid lipase; diacylglycerols; fatty acids
B) triacylglycerol lipase; fatty acids; glycerol
C) triacylglycerol lipase; fatty acids; glycerol
D) pancreatic lipase; monoacylglycerols; fatty acids
E) pancreatic lipase; glycerol; fatty acids

Question 5

Chylomicrons:

A) are formed in adipose tissue.
B) are primary energy sources for the brain.
C) transport dietary triacylglycerols through the bloodstream.
D) are formed in and secreted by the liver.
E) contain more phospholipid than triacylglycerol molecules.

Question 6

The first three reactions of β-oxidation of saturated fatty acids are analogous to which sequence of metabolic reactions already discussed?

A) succinate → fumarate → malate → oxaloacetate
B) isocitrate → α-ketoglutarate → succinate → fumarate
C) oxaloacetate → citrate → isocitrate → α-ketoglutarate
D) phosphoenolpyruvate → pyruvate → acetyl-CoA → citrate
E) α-ketoglutarate → succinyl-CoA → succinate → fumarate

Question 7

For the complete oxidation of a saturated fatty acid with 16 carbons, how many times must the β-oxidation cycle be repeated?

A) 4
B) 7
C) 8
D) 6
E) 16

Question 8

The product of β-oxidation, acetyl-CoA, can be used for all EXCEPT:

A) synthesis of ketone bodies.
B) synthesis of amino acids.
C) catabolism in the TCA cycle.
D) synthesis of glucose.
E) none of the above.

Question 9

Absorbed lipids are condensed with glycerol in the epithelial cells into ____ and re-packaged into ____ that are initially transported by the ____ system.

A) phospholipids; VLDL; lymphatic
B) triacylglycerols; VLDL; portal
C) triacylglycerols; LDL; portal
D) triacylglycerols; chylomicron; lymphatic
E) triacylglycerols; VLDL; lymphatic

Question 10

Fatty acids are mobilized from adipose cells in response to all of the hormones EXCEPT:

A) ACTH (adrenocorticotropic hormone).
B) glucagon.
C) insulin.
D) epinephrine (adrenaline).
E) all are true.

Question 11

Which of the following correctly describes the sequence of events for the conversion of a fatty acid to CO₂?

A) carnitine shuttle, activation to acyl CoA, β-oxidation, TCA cycle
B) activation to acyl CoA, β-oxidation, carnitine shuttle, TCA cycle
C) activation to acyl CoA, carnitine shuttle, β-oxidation, TCA cycle
D) TCA cycle, activation to acyl CoA, β-oxidation, carnitine shuttle
E) TCA cycle, activation to acyl CoA, carnitine shuttle, β-oxidation

Question 12

L-Hydroxyacyl-CoA dehydrogenase is analogous in catalytic activity to what enzyme of the citric acid cycle?

A) aconitase
B) citrate synthase
C) isocitrate dehydrogenase
D) α-ketoglutarate dehydrogenase
E) malate dehydrogenase

Question 13

Enoyl-CoA hydratase belongs to what class of enzymes?

A) oxidoreductases
B) hydrolases
C) lyases
D) ligases
E) transferases

Question 14

How many NADH are generated from the complete oxidation of palmitoyl-CoA to CO₂?

A) 7 from β-oxidation and 24 from the TCA
B) 8 from β-oxidation and 24 from the TCA
C) 7 from β-oxidation and 21 from the TCA
D) 7 from β-oxidation and 28 from the TCA
E) 8 from β-oxidation and 24 from the TCA

Question 15

All are characteristics of acyl-CoA dehydrogenase EXCEPT:

A) oxidation of the Cα-Cβ bond.
B) comes in at least three isozymes each specific for fatty acids of differing chain lengths.
C) uses tightly bound FAD.
D) electrons are transferred to electron transfer flavoprotein (ETF) and on to Q of the electron transport system.
E) all are correct.

Question 16

The sequence for activation of the release of fatty acids from adipose cells is:
A)protein kinase activation
B)cAMP production
C)triacylglycerol lipase activation
D)hormone binding receptor
E)adenylyl cyclase activation
F)
Diacylglycerol lipase and monoacylglycerol lipase activity

A) D, E, B, A, C, F
B) D, B, A, E, F, C
C) D, B, C, F, A, E
D) D, B, F, A, C, E
E) B, F, A, D, E, C

Question 17

____ carries long-chain fatty acyl groups across the ____ membrane.

A) Biotin; intestinal
B) Carnitine; plasma
C) CoA-SH; plasma
D) Carnitine; inner mitochondrial
E) TPP; outer mitochondrial

Question 18

The primary storage form of lipid is ____ and it is normally stored in the ____.

A) phospholipid; liver
B) cholesterol; muscles
C) monoacylglycerol; adipocytes
D) triacylglycerols; adipocytes
E) triacylglycerols; liver

Question 19

The first oxidation in the β-oxidation of saturated fatty acids is catalyzed by ____ and is the conversion of ____.

A) β-hydroxyacyl-CoA dehydrogenase; a primary alcohol to an aldehyde.
B) acyl-CoA dehydrogenase; a carbon-carbon single bond to a carbon-carbon double bond.
C) acyl-CoA dehydrogenase; a secondary alcohol to a ketone.
D) β-hydroxyacyl-CoA dehydrogenase; an aldehyde to a carboxylic acid.
E) acyl-CoA dehydrogenase; an aldehyde to a ketone.

Question 20

The correct sequence for transport of fatty acyl groups from the cytosol to the matrix is:
A)carnitine acyltransferase I
B)tranaslocase of carnitine and O-acylcarnitine
C)carnitine acyltransferase II
D)fatty acyl-CoA synthesis
E)O-acylcarnitine
F)
Fatty acyl-CoA in matrix

A) C, B, D, A, F, E
B) D, B, F, E, A, C
C) D, E, A, C, B, F
D) D, A, E, B, C, F
E) A, D, E, B, C, F

Question 21

How are long chain fatty acid derivatives transferred into the mitochondrial matrix?​

Question 22

What are the three most common ketone bodies?

A) acetone, butyrate and acetyl-CoA
B) acetoacetate, hydroxyacetone phosphate and butyrate
C) acetone, β-hydroxybutyrate and acetoacetate
D) acetoacetate, acetyl-CoA and acetone
E) butyrate, acetoacetate and acetone

Question 23

Propionyl-CoA is a product of β-oxidation of ____ and is ultimately converted to the TCA cycle intermediate, ____.

A) odd-chain fatty acids; citrate
B) even-chain fatty acids; isocitrate
C) odd-chain fatty acids; succinyl-CoA
D) even-chain fatty acids; succinate
E) none are true

Question 24

Which of the following correctly explains the distribution of lipids from the diet?

A) All dietary lipids are all packaged into chylomicrons
B) Dietary triacylglycerols are packaged into chylomicrons while dietary cholesterol is packaged into low density lipoproteins
C) Dietary lipids are packaged into very low density lipoproteins which lose triacylglycerol to become low density lipoproteins
D) Dietary lipids are packaged into low density lipoproteins which lose cholesterol to become very low density lipoproteins
E) None of the above

Question 25

Ketone bodies are synthesized in the:

A) cytosol of muscle.
B) mitochondria of liver.
C) endoplasmic reticulum of heart.
D) plasma membrane of brain.
E) none of the above.

Question 26

How many NADH can be produced by the complete oxidation of β-hydroxybutyrate? The conversion of a molecule of β-hydroxybutyrate to 2 molecules of acetyl CoA produces 1 NADH.

A) 3
B) 4
C) 6
D) 7
E) 9

Question 27

In ketone body biosynthesis, the HMG-CoA lyase is mechanistically the reverse of the first half of the reaction catalyzed by:

A) aconitase.
B) β-hydroxybutyrate dehydrogenase.
C) citrate synthase.
D) pyruvate dehydrogenase.
E) succinyl-CoA synthase.

Question 28

During β-oxidation of certain unsaturated fatty acids, cis-Δ³-fatty acyl-CoAs are formed that must be converted to ____-fatty acyl-CoAs by the enzyme ____.

A) cis-Δ²; acyl-CoA dehydrogenase
B) trans-Δ²; acyl-CoA dehydrogenase
C) trans-Δ²; enoyl-CoA dehydrogenase
D) trans-Δ³; enoyl-CoA dehydrogenase
E) trans-Δ²; acyl-CoA isomerase

Question 29

Discuss the significance of the enzyme enoyl-CoA isomerase in the β-oxidation of unsaturated fatty acids.​

Question 30

Which of the following correctly describes the sequence of events in the conversion of a triacylglycerol to acetyl-CoA?

A) lipolysis, albumin transport, carnitine shuttle, activation to acyl CoA, β-oxidation
B) albumin transport, carnitine shuttle, lipolysis, activation to acyl CoA, β-oxidation
C) lipolysis, albumin transport, activation to acyl CoA, carnitine shuttle, β-oxidation
D) albumin transport, activation to acyl CoA, carnitine shuttle, lipolysis, β-oxidation
E) none of the above are correct

Question 31

Which of the following is required by thr 2,4-dienoyl-CoA reductase enzyeme during the oxidation of polyunsaturated fatty acids?

A) NADH
B) NADPH
C) FADH₂
D) coenzyme Q (QH₂)
E) none of the above

Question 32

Ketone bodies are transported to the tissues of utilization:

A) complexed to serum albumin.
B) incorporated into VLDLs.
C) complexed to fatty acid binding protein.
D) freely dissolved in serum.
E) but require insulin to enter target tissues.

Question 33

Discuss the functions of the three enzymes involved in the β-oxidation of odd-carbon fatty acids.​

Question 34

The brain normally uses ____ as its source of metabolic energy, but during starvation ____ may be the major source of energy.

A) glucose; ketone bodies
B) ketone bodies; fatty acids
C) fatty acids; amino acids
D) amino acids; glucose
E) all are true

Question 35

Which of the following statements regarding ketone bodies is true?

A) They are made in the liver as a result of excessive fatty acid oxidation
B) While normally used by muscle tissue, under starvation conditions, they are used by the brain and red blood cells
C) Excessive levels of β-hydroxybutyrate in the blood stream will result in an increase of the blood pH
D) Acetone is used as a fuel in the muscle by first undergoing isomerization followed by oxidation to propionyl CoA
E) Both A and B are correct

Question 36

All are true for methylmalonyl-CoA mutase EXCEPT:

A) does hemolytic cleavage of Co³⁺ -C bond.
B) vitamin B₁₂-dependent.
C) classic B₁₂-enzyme catalyzed rearrangement.
D) produces succinyl-CoA.
E) all are true.

Question 37

All are true for 2,4-dienoyl-CoA reductase EXCEPT:

A) reduces trans-Δ², cis-Δ⁴ double bonds to trans-Δ³.
B) uses NADPH.
C) involved in saturated fatty acid catabolism.
D) cooperates with β-oxidation in fatty acid oxidation.
E) all are true.

Question 38

Ketone body carbons enter the major metabolic pathways of the cells by conversion to:

A) acetyl-CoA.
B) butyrate.
C) citrate.
D) pyruvate.
E) glucose-6-phosphate.

Question 39

What are the β-oxidation products of oleic acid (18:1Δ⁹) and how many ATP equivalents are required for activation?

A) 8 acetyl CoA, 8 NADH, 7 FADH₂, 1 ATP equivalent
B) 9 acetyl CoA, 8 NADH, 7 FADH₂, 2 ATP equivalents
C) 8 acetyl CoA, 7 NADH, 7 FADH₂, 1 ATP equivalent
D) 8 acetyl CoA, 7 NADH, 6 FADH₂, 2 ATP equivalents
E) 9 acetyl CoA, 9 NADH, 8 FADH₂, 2 ATP equivalents

Question 40

Describe the final step in the β-oxidation cycle.​

Question 41

How is the ketone body β-hydroxybutyrate synthesized from acetyl-CoA?​