Quiz 14

In a mitochondrion that expresses a c-ring of 12 subunits the total number of ATP produced per β-oxidation of a 16-carbon saturated fatty acid is: A. 106 B. 96 C. 88 D. 86 E. 80

1st step, calculating P/O ratios: a. 12 subunits = 12 protons for 360-degree turn of the gamma-shaft making 3-ATP. b. Each ATP requires 1 additional proton to move Pi through the phosphate translocase making for a total of 15 protons to make 3 ATP. c. This means it take 5 protons to make 1 ATP (15 protons/3 ATP) d. NADH pumps 10 protons from N to P-side. This means the P/O ratio for NADH is 2 ATP/NADH (10 protons per NADH/5 protons per ATP) e. FADH2 pumps 6 protons from N to P-side. This means the P/O ratio for FADH2 is 1.2 ATP/FADH2 (6 protons per NADH/5 protons per ATP) 2nd step, calculating number of acetyl-CoA, NADH, and FADH2 produced by β-oxidation. a. Number of acetyl-CoA = number of carbons in fatty acid/2. In this case 16/2 = 8 acetyl-CoA. b. Number of NADH and FADH2 = number of rounds of β-oxidation. Number of rounds of β-oxidation = (number of carbons in fatty acid/2 - 1. In this case: (16/2)-1 = 7. 3rd step, calculating number of total NADH and FADH2 made from the citric acid cycle. a. Each acetyl-CoA produces 3 NADH per turn of the cycle. Total NADH from acetyl-CoA = 8 x 3 = 24. b. Each acetyl-CoA produces 1 FADH2 per turn of the cycle. Total FADH2 from acetyl-CoA = 8. 4th step, calculating number of ATP made from NADH and FADH2 a. Total NADH = 24 + 7 = 31. Total ATP = 31 NADH x 2 ATP/NADH = 62 ATP. b. Total FADH2 = 8 + 7 = 15. Total ATP = 15 FADH2 x 1.2 ATP/FADH2 = 18 ATP. 5th step, calculating number of ATP from the citric acid cycle substrate level phosphorylation. a. Each acetyl-CoA produces 1 ATP per turn of the cycle. Total ATP from acetyl-CoA = 8. 6th step, calculation total number of ATP from β-oxidation of 16:0. a. 62 ATP + 18 ATP + 8 ATP = 88 ATP b. Two ATP must be subtracted from this total as two ATP equivalents are used to attach CoA to the fatty acid. c. Total = 86 ATP.

β-oxidation is a metabolic pathway that removes 2-carbons from a lipid and, at the same time, oxidizes the β-carbon. Considering this pathway, which of the following are true? A. β-oxidation, like glycolysis, is capable of carrying out substrate-level phosphorylation. B. β-oxidation of a 20-carbon saturated lipid requires 10 rounds in order to make 10 acetyl-CoA. C. β-oxidation, like glycolysis, takes place in the cytosol. D. Produces 4 NADH and 2 FADH2 for every two carbons that are oxidized to CO2 (assume the citric acid cycle is coupled to β-oxidation). (correct) E. B) and D).

D. Produces 4 NADH and 2 FADH2 for every two carbons that are oxidized to CO2 (assume the citric acid cycle is coupled to β-oxidation). (correct)

β-oxidation is integrated with other pathways in cellular metabolism. As such, it is regulated in order to maintain cellular steady-states. Considering this regulation and pathway, which of the following are true? A. Increased expression of CATI can lead to increased flux through β-oxidation. B. Glucagon signaling activates PKA that will subsequently lead to a reduction in flux through β-oxidation. C. Insulin increases flux through lipid biogenesis by increasing malonyl-CoA production which, subsequently, activates the carnitine shuttle. D. Activation of PPARα leads to increased expression of β-oxidation genes. E. A) and D). (correct)

E. A) and D). (correct)

β-oxidation is integrated with other pathways in cellular metabolism. Considering this integration, which of the following are true? A. Glucagon signaling within a liver cell will increase flux through gluconeogenesis and lipid biogenesis. B. Insulin signaling within a liver cell leads to increased flux through glycolysis and conversion of the resulting pyruvate to lipids via the intermediate malonyl-CoA. C. Increased flux through gluconeogenesis in a liver cell is coupled with increased flux through β-oxidation in order to supply ATP to the cell. D. Covalent modification is the only means of regulating β-oxidation. E. A), B), and C). F. B) and C). (correct)

F. B) and C). (correct)

enoyl-CoA hydratase

Places a hydroxyl group on the β-carbon. (correct)

β-hydroxyacyl-CoA dehydrogenase

Transfers electron to the ETC via complex I. (correct)

Acyl-CoA dehydrogenase

Transfers electrons to the ETC via electron transferring flavoprotein (ETF). (correct)

Thiolase

Utilizes CoA to catalyze its reaction. (correct)