Deck 17: Fatty Acid Catabolism

Question 1

Which of the following is (are) true of the oxidation of 1 mol of palmitate (a 16-carbon saturated fatty acid; 16:0) by the β-oxidation pathway, beginning with the free fatty acid in the cytoplasm?
1. Activation of the free fatty acid requires the equivalent of two ATPs.
2. Inorganic pyrophosphate (PPi) is produced.
3. Carnitine functions as an electron acceptor.
4. 8 mol of FADH2 are formed.
5. 8 mol of acetyl-CoA are formed.
6. There is no direct involvement of NAD+.

A)1 and 5 only
B)1,2,and 5
C)1,2,and 6
D)1,3,and 5
E)5 only

Answer 1

1,2,and 5

Question 2

Complete oxidation of 1 mole of which fatty acid would yield the most ATP?

A)16-carbon saturated fatty acid
B)18-carbon mono-unsaturated fatty acid
C)16-carbon mono-unsaturated fatty acid
D)16-carbon poly-unsaturated fatty acid
E)14-carbon saturated fatty acid

Answer 2

18-carbon mono-unsaturated fatty acid

Question 3

The role of hormone-sensitive triacylglycerol lipase is to:

A)hydrolyze lipids stored in the liver.
B)hydrolyze membrane phospholipids in hormone-producing cells.
C)hydrolyze triacylglycerols stored in adipose tissue.
D)synthesize lipids in adipose tissue.
E)synthesize triacylglycerols in the liver.

Answer 3

hydrolyze triacylglycerols stored in adipose tissue.

Question 4

Which of the following is not true regarding the oxidation of 1 mol of palmitate (16:0)by the $\beta$ -oxidation pathway?

A)1 mol of ATP is needed.
B)8 mol of acetyl-CoA are formed.
C)8 mol of FADH₂ are formed.
D)AMP and PP_i are formed.
E)The reactions occur in the mitochondria.

Question 5

Lipoprotein lipase acts in:

A)hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues.
B)intestinal uptake of dietary fat.
C)intracellular lipid breakdown of lipoproteins.
D)lipoprotein breakdown to supply needed amino acids.
E)none of the above.

Question 6

Which of the following statements concerning the $\beta$ -oxidation of fatty acids is true?

A)About 1200 ATP molecules are ultimately produced per 20-carbon fatty acid oxidized.
B)One FADH₂ and two NADH are produced for each acetyl-CoA.
C)The free fatty acid must be carboxylated in the $\beta$ position by a biotin-dependent reaction before the process of $\beta$ -oxidation commences.
D)The free fatty acid must be converted to a thioester before the process of $\beta$ -oxidation commences.
E)Two NADH are produced for each acetyl-CoA.

Question 7

Saturated fatty acids are degraded by the stepwise reactions of $\beta$ -oxidation,producing acetyl-CoA.Under aerobic conditions,how many ATP molecules would be produced as a consequence of removal of each acetyl-CoA?

A)2
B)3
C)4
D)5
E)6

Question 8

Which of these is able to cross the inner mitochondrial membrane?

A)Acetyl-CoA
B)Fatty acyl-carnitine
C)Fatty acyl-CoA
D)Malonyl-CoA
E)None of the above can cross.

Question 9

Transport of fatty acids from the cytoplasm to the mitochondrial matrix requires:

A)ATP,carnitine,and coenzyme A.
B)ATP,carnitine,and pyruvate dehydrogenase.
C)ATP,coenzyme A,and hexokinase.
D)ATP,coenzyme A,and pyruvate dehydrogenase.
E)carnitine,coenzyme A,and hexokinase.

Question 10

The conversion of palmitoyl-CoA (16:0)to myristoyl-CoA (14:0)and 1 mol of acetyl-CoA by the $\beta$ -oxidation pathway results in the net formation of:

A)1 FADH₂ and 1 NADH.
B)1 FADH₂ and 1 NADPH.
C)1 FADH₂,1 NADH,and 1 ATP.
D)2 FADH₂ and 2 NADH.
E)2 FADH₂,2 NADH,and 1 ATP.

Question 11

Carnitine is:

A)a 15-carbon fatty acid.
B)an essential cofactor for the citric acid cycle.
C)essential for intracellular transport of fatty acids.
D)one of the amino acids commonly found in protein.
E)present only in carnivorous animals.

Question 12

What is the correct order of function of the following enzymes of -oxidation?
1. β-Hydroxyacyl-CoA dehydrogenase
2. Thiolase
3. Enoyl-CoA hydratase
4. Acyl-CoA dehydrogenase

A)1,2,3,4
B)3,1,4,2
C)4,3,1,2
D)1,4,3,2
E)4,2,3,1

Question 13

Which of the following is (are) true of the -oxidation of long-chain fatty acids?
1. The enzyme complex that catalyzes the reaction contains biotin.
2. FADH₂ serves as an electron carrier.
3. NADH serves as an electron carrier.
4. Oxidation of an 18-carbon fatty acid produces six molecules of propionyl-CoA.
5. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA.

A)1,2,and 3
B)1,2,and 5
C)2,3,and 4
D)2,3,and 5
E)3 and 5 only

Question 14

Free fatty acids in the bloodstream are:

A)bound to hemoglobin.
B)carried by the protein serum albumin.
C)freely soluble in the aqueous phase of the blood.
D)nonexistent;the blood does not contain free fatty acids.
E)present at levels that are independent of epinephrine.

Question 15

Which compound is an intermediate of the $\beta$ -oxidation of fatty acids?

A)CH₃-(CH₂)₂₀-CO-COOH
B)CH₃-CH₂-CO-CH₂-CO-OPO₃^2-
C)CH₃-CH₂-CO-CH₂-OH
D)CH₃-CH₂-CO-CO-S-CoA
E)CH₃-CO-CH₂-CO-S-CoA

Question 16

Fatty acids are activated to acyl-CoAs and the acyl group is further transferred to carnitine because:

A)acyl-carnitines readily cross the mitochondrial inner membrane,but acyl-CoAs do not.
B)acyl-CoAs easily cross the mitochondrial membrane,but the fatty acids themselves will not.
C)carnitine is required to oxidize NAD⁺ to NADH.
D)fatty acids cannot be oxidized by FAD unless they are in the acyl-carnitine form.
E)None of the above is true.

Question 17

If the 16-carbon saturated fatty acid palmitate is oxidized completely to carbon dioxide and water (via the $\beta$ -oxidation pathway and the citric acid cycle),and all of the energy-conserving products are used to drive ATP synthesis in the mitochondrion,the net yield of ATP per molecule of palmitate is:

A)3)
B)10.
C)25.
D)108.
E)1000.

Question 18

Which of the following statements apply (applies) to the β-oxidation of fatty acids?
1. The process takes place in the cytosol of mammalian cells.
2. Carbon atoms are removed from the acyl chain one at a time.
3. Before oxidation, fatty acids must be converted to their CoA derivatives.
4. NADP+ is the electron acceptor.
5. The products of β-oxidation can directly enter the citric acid cycle for further oxidation.

A)1 and 3 only
B)1,2,and 3
C)1,2,and 5
D)3 and 5 only
E)4 only

Question 19

If an aerobic organism (e.g. ,the bacterium E.coli)were fed each of the following four compounds as a source of energy,the energy yield per mole from these molecules would be in the order:

A)alanine > glucose > palmitate
B)glucose > alanine > palmitate
C)glucose > palmitate > alanine
D)palmitate > alanine > glucose
E)palmitate > glucose > alanine

Question 20

The glycerol produced from the hydrolysis of triacylglycerides enters glycolysis as:

A)glucose.
B)glucose-6-phosphate.
C)dihydroxyacetone phosphate.
D)pyruvate.
E)glyceryl CoA.

Question 21

In the citric acid cycle,a double bond is introduced into a four-carbon compound containing the -CH₂-CH₂- group,producing fumarate.Show a similar reaction that occurs in the $\beta$ -oxidation pathway.

Question 22

The carbon atoms from a fatty acid with an odd number of carbons will enter the citric acid cycle as acetyl-CoA and:

A)butyrate.
B)citrate.
C)malate.
D)succinyl-CoA.
E)( $\alpha$ -ketoglutarate.)

Question 23

The following fatty acid,in which the indicated carbon is labeled with ¹⁴C,is fed to an animal: ¹⁴CH₃(CH₂)₉COOH
After allowing 30 minutes for fatty acid $\beta$ -oxidation,the label would most likely be recovered in:

A)acetyl-CoA.
B)beta-hydroxy butyryl-CoA.
C)both acetyl-CoA and propionyl-CoA.
D)palmitoyl-CoA.
E)propionyl-CoA.

Question 24

When comparing the $\beta$ -oxidation and $\omega$ -oxidation pathways,which one of the following statements is correct?

A)( $\beta$ -oxidation and $\omega$ -oxidation occur in the cytoplasm.)
B)( $\beta$ -oxidation occurs at the carboxyl end of the fatty acid whereas $\omega$ oxidation occurs at the methyl end.)
C)( $\beta$ -oxidation occurs at the methyl end of the fatty acid,whereas $\omega$ -oxidation occurs at the carboxyl end.)
D)( $\beta$ -oxidation occurs mainly in the cytoplasm,whereas $\omega$ -oxidation occurs mainly in the mitochondria.)
E)( $\beta$ -oxidation occurs mainly in the mitochondria,whereas $\omega$ -oxidation occurs mainly in the cytoplasm.)

Question 25

Draw the third and fourth steps in the $\beta$ -oxidation of a saturated fatty acid.Show structures,name enzymes,and indicate where any cofactors participate.

Question 26

The oxidation of acetyl-CoA added to isolated,intact mitochondria is stimulated strongly by carnitine.Why?

Question 27

Why is it more efficient to store energy as lipid rather than as glycogen?

Question 28

In the disease sprue,vitamin B₁₂ (cobalamin)is poorly absorbed in the intestine,resulting in B₁₂ deficiency.If each of the following fatty acids were in the diet,for which one would the process of fatty acid oxidation be most affected in a patient with sprue?

A)CH₃(CH₂)₁₀COOH
B)CH₃(CH₂)₁₁COOH
C)CH₃(CH₂)₁₂COOH
D)CH₃(CH₂)₁₄COOH
E)CH₃(CH₂)₁₈COOH

Question 29

Explain why lipases are required in both the intestine and in the bloodstream?

Question 30

The metabolite that regulates the activity of carnitine acyl transferase I is:

A)acetyl-CoA.
B)carnitine-CoA.
C)malonyl-CoA.
D)NADH.
E)CoA.

Question 31

Ketone bodies are formed in the liver and transported to the extrahepatic tissues mainly as:

A)acetoacetyl-CoA.
B)acetone.
C)( $\beta$ -hydroxybutyric acid.)
D)( $\beta$ -hydroxybutyryl-CoA.)
E)lactic acid.

Question 32

Explain the chemical reason why the addition of water across the double bond in the second step of $\beta$ -oxidation occurs with the OH adding at the $\beta$ -carbon,not the $\alpha$ -carbon.Also,how does addition at the $\beta$ -carbon aid in the subsequent step(s)of $\beta$ -oxidation?

Question 33

For each two-carbon increase in the length of a saturated fatty acid chain,how many additional moles of ATP can be formed upon complete oxidation of one mole of the fatty acid to CO₂ and H₂O?

Question 34

Write a balanced equation for the $\beta$ -oxidation of palmitoyl-CoA,a 16-carbon,fully saturated fatty acid,and indicate how much of each product is formed.

Question 35

The major site of formation of acetoacetate from fatty acids is the:

A)adipose tissue.
B)intestinal mucosa.
C)kidney.
D)liver.
E)muscle.

Question 36

Draw the first two steps of $\beta$ -oxidation of saturated fatty acids.Show structures and indicate where any cofactors participate.

Question 37

One of the steps in fatty acid oxidation in mitochondria involves the addition of water across a double bond.What is the next step in the process? Show structures and indicate where any cofactor(s)participate(s).

Question 38

In the first step of fatty acid oxidation,the fatty acid (R-COOH)is converted to its coenzyme A derivative in the following reaction:
R-COOH + ATP + CoA-SH $\rightarrow$ R-CO-S-CoA + AMP + PP_i
The standard free-energy change ( $\Delta$ G'° )for this reaction is -15 kJ/mol
What will tend to make the reaction even more favorable when it takes place within a cell?

Question 39

During $\beta$ -oxidation of fatty acids,___________ is produced in peroxisomes but not in mitochondria.

A)acetyl-CoA
B)FADH₂
C)H₂O
D)H₂O₂
E)NADH

Question 40

Which enzyme is the major regulatory control point for $\beta$ -oxidation?

A)Pyruvate carboxylase
B)Carnitine acyl transferase I
C)Acetyl CoA dehydrogenase
D)Enoyl CoA isomerase
E)Methylmalonyl CoA mutase

Question 41

What are the two major differences between the $\beta$ -oxidation pathway in mitochondria and the $\beta$ -oxidation pathway in peroxisomes?

Question 42

Briefly explain the basic concept of $\omega$ -oxidation.

Question 43

Draw the structure of one ketone body,and describe circumstances under which you would expect to find high concentrations of this compound in the urine of a human.

Question 44

An experimenter studying the oxidation of fatty acids in extracts of liver found that when palmitate (16:0)was provided as substrate,it was completely oxidized to CO₂.However,when undecanoic acid (11:0)was added as substrate,incomplete oxidation occurred unless he bubbled CO₂ through the reaction mixture.The addition of the protein avidin,which binds tightly to biotin,prevented the complete oxidation of undecanoic acid even in the presence of CO₂,although it had no effect on palmitate oxidation.Explain these observations in light of what you know of fatty acid oxidation reactions.

Question 45

Describe the steps in the metabolic pathway in which cells oxidize a four-carbon,straight-chain,saturated fatty acid (butyrate;4:0)to the fragments that enter the citric acid cycle.Show the structures of intermediates and products,and indicate where any cofactor(s)participate(s).

Question 46

Describe the steps in the metabolic pathway in which cells oxidize a five-carbon,straight-chain,saturated fatty acid (valerate;5:0)to the fragments that enter the citric acid cycle.Show the structures of intermediates and products,and indicate where any cofactor(s)participate(s).

Question 47

Two vitamins,biotin and vitamin B₁₂,play crucial roles in the metabolism of propionic acid (propionate).Explain this by showing the steps in which each is essential in propionate metabolism.

Question 48

If you received a laboratory report showing the presence of a high concentration of ketone bodies in the urine of a patient,what disease would you suspect? Why do ketone bodies accumulate in such patients?

Question 49

Write a balanced equation for the complete oxidation (to acetyl-CoA and any other products that might be formed)of pelargonic acid,CH₃(CH₂)₇COOH.

Question 50

The total degradation of a fatty acid with an odd number of carbons yields acetyl-CoA and another compound,X.Show the structure of X and describe the pathway by which it is converted into a citric acid cycle intermediate,including where any cofactors participate.