Question

1. If 1 mol of a fatty acyl-CoA containing 20 carbon atoms undergoes only four rounds of beta oxidation, how many mol of ATP are produced from the complete aerobic catabolism of the products of these four rounds? (The remaining fatty acyl-CoA is NOT catabolized further.)

a. 12 ATP

b. 52 ATP

c. 34.5 ATP

d. 56 ATP

e. 42 ATP

2. Complete oxidation of 1 mole of which fatty acid would yield the least 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

3. Which statement is FALSE regarding acyl-carrier protein (ACP)?

a. ACP is transiently attached to malonyl-CoA during fatty acid elongation.

b. ACP contains a pantothenate-derived prosthetic group.

c. ACP carries reaction intermediates from one active site to the next in fatty acid synthesis.

d. ACP associates as a separate polypeptide with fatty acid synthase 1 in vertebrates.

e. Fatty acyl chains on ACP are transferred to a cysteine on beta-ketoacyl-ACP synthase during fatty acid synthesis.

Answer 1

1. If 1 mol of a fatty acyl-CoA containing 20 carbon atoms undergoes only four rounds of beta oxidation, how many mol of ATP are produced from the complete aerobic catabolism of the products of these four rounds? (The remaining fatty acyl-CoA is NOT catabolized further.)

56 ATP.

4 rounds of β-oxidation generate 4 FADH2, 4 NADH, and 4 acetyl-CoA.

1 Acetyl-CoA via TCA cycle generates 3 NADH, 1 FADH2, and 1 GTP.

4 Acetyl-CoA via TCA cycle generates 12 NADH, 4 FADH2, and 4 GTP.

Totally, it is

16 NADH = 48 ATP (16 x 2.5) (1 NADH generates 2.5 ATPs)

8 FADH2 = 16 ATP (8 x 1.5) 1 FADH2 generates 1.5 ATPs)

4 GTP = 4 ATP

Total = 56 ATPs.

2. Complete oxidation of 1 mole of which fatty acid would yield the least ATP?

16-carbon poly-unsaturated fatty acid.

Presence of one or more than one double bonds reduces ATP production via β-oxidation and TCA cycle. Among all the options, this one (16-carbon poly-unsaturated fatty acid) has more double bonds. So, it would yield the least ATP.

3. Which statement is FALSE regarding acyl-carrier protein (ACP)?

ACP associates as a separate polypeptide with fatty acid synthase 1 in vertebrates.

Other options are true regarding ACP.

ACP contains is a pantothenate-derived prosthetic group and transiently attached to malonyl-CoA during fatty acid elongation. It carries reaction intermediates from one active site to the next in fatty acid synthesis. Fatty acyl chains on ACP are transferred to a cysteine on beta-ketoacyl-ACP synthase during fatty acid synthesis.