Chapter 17 Fatty Acid Catabolism (Ed. 6 test bank)

Question 1

Lipoprotein lipase acts in:

Answer 1

Hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues

Question 2

The role of hormone-sensitive triacylglycerol lipase is to:

Answer 2

Hydrolyze triacylglycerols stored in adipose tissue

Question 3

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

Answer 3

ATP, carnitine, and coenzyme A

Question 4

Carnitine is:

Answer 4

Essential for intracellular transport of fatty acids

Question 5

What is the correct order of function of the following enzymes of beta-oxidation?

1. Beta-hydroxyacyl-CoA dehydrogenase
2. Thiolase
3. Enoyl-CoA hydratase
4. Acyl-CoA dehydrogenase

Answer 5

1. Acyl-CoA dehydrogenase
2. Enoyl-CoA hydratase
3. Beta-hydroxyacyl-CoA dehydrogenase
4. Thiolase

Question 6

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

Answer 6

4

Question 7

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 beta-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.
2. Carnitine functions as an electron acceptor. 4. 8 mol of FADH2 are formed.
3. 8 mol of acetyl-CoA are formed.
4. There is no direct involvement of NAD+.

Answer 7

1, 2, and 5

Question 8

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 8

18-carbon monounsaturated fatty acid

Question 9

Which of the following statements apply (applies) to the beta-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 beta-oxidation can directly enter the citric acid cycle for further oxidation.

Answer 9

3 and 5 only

Question 10

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

Answer 10

The free fatty acid must be converted to a thioester before the process of beta-oxidation commences

Question 11

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:

Answer 11

1 FADH_2 and 1 NADH

Question 12

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

Answer 12

8 mol of FADH_2 are formed

Question 13

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 (16:0)
B) glucose > alanine > palmitate
C) glucose > palmitate > alanine
D) palmitate > alanine > glucose
E) palmitate > glucose > alanine

Answer 13

Palmitate > glucose > alanine

Question 14

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

Answer 14

Succinyl-CoA

Question 15

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

Answer 15

First, the energy yield per gram of lipid (about 38 kJ/g) is more than twice that for carbohydrate (about 17 kJ/g).

Second, lipid is stored as anhydrous lipid droplets, but carbohydrates such as glycogen and starch are stored hydrated, and the water of hydration roughly triples the effective weight of the carbohydrate, reducing the energy yield to about 6 kJ/g.

Question 16

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 –> R–CO–S–CoA + AMP + PPi

The standard free-energy change (Delta-G’°) for this reaction is –15 kJ/mol

What will tend to make the reaction more favorable when it takes place within a cell?

Answer 16

The hydrolysis of PPi by inorganic pyrophosphatase, for which Delta-G’° is –19 kJ/mol, makes the
overall Delta-G’° more negative.

Question 17

The beta-oxidation of fatty acids begins with this activation reaction:

R–CH2–CH2–CH2–COOH + ATP + CoA–SH –> R–CH2–CH2–CH2–CO–S–CoA + AMP + PPi

What are the next two steps (after transport into the mitochondria)?

Show structures and indicate where any cofactors participate.

Answer 17

The reactions are those catalyzed by fatty acyl–CoA dehydrogenase and enoyl hydratase.

See Fig. 17-8a, p. 653.

Question 18

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).

Answer 18

The reaction is that catalyzed by beta-hydroxyacyl-CoA dehydrogenase, for which NAD+ is cofactor. See Fig. 17-8a, p. 653.

Question 19

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?

Answer 19

Each —CH2—CH2— unit yields 14 extra ATP molecules. The two oxidations of the beta-oxidation pathway produce 1 FADH2 and 1 NADH, which yield 1.5 and 2.5 ATP, respectively, by
oxidative phosphorylation.

The extra acetyl-CoA, when oxidized via the citric acid cycle, yields another 10 ATP equivalents: 3 NADH, 1 FADH2, and 1 ATP or GTP.

Question 20

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.

Answer 20

Oxidation of odd-chain fatty acid yields acetyl-CoA + propionyl-CoA. The reaction CO2 +
propionyl-CoA –> methylmalonyl-CoA is catalyzed by propionyl-CoA carboxylase, a biotin- containing enzyme, which is therefore inhibited by avidin.