Question

Topic :  Fatty Acid Catabolism

4.How many rounds of the TCA cycle will be used to process the acetyl-CoA produced from β-oxidation of palmitic acid? How many NADH and how many FADH2 will this produce? How many ATP will be made by substrate-level phosphorylation?


5. Given the entry points of NADH and FADH2 produced by β-oxidation into the ETS, how many net ATP can be obtained from the complete oxidation of palmitic acid? (Don’t forget that some ATP was consumed in the initial activation of the fatty acid!)


6. Given that complete oxidation of glucose (a 6-carbon sugar) yields 32 ATP, compare the energy yield on a per-carbon basis from palmitic acid vs. glucose. Does this comparison make sense to you? Explain.

Answer 1

4.Beta oxidation of palmitic acid will yield 8 acetyl CoA by 7 round of  fatty acid beta oxidation.One acetyl CoA will catabolised in each TCA cycle.Thus there will be be 8 round of TCA cycle.

Palmitic acid catabolism will produce 7 NADH 7FADH and 8 acetyl CoA. Each acetyl coa in TCA cycle will produce 3NADH 1FADH and 1 GTP thus a total of 10ATP(2.5 ATP by NADH, 1.5 ATP by FADH and 1 ATP) by a acetyl coa. Substrate level phosphorylation produce 8 ATP in which 2 is used for activation thus the net ATP produced by substrate level phosphorylation will be 6ATP.

5.ATP produced by complete oxidation of palmitic acid will be

8 acetyl coa producing 80 ATP , 7NADH producing 17.5 ATP (7*2.5=17.5), 7FADH producing 10.5 ATP ( 7×1.5=10.5) and 2 ATP is used for activation of fatty acid.so (80+17.5+10.5)- 2 = 106 ATP.

6.6 C glucose produce 32 ATP an average of 5.3 ATP per Carbon and 16 C palmitic acid produce 106 ATP an average of 6.625 ATP per carbon.

Thus fatty acid oxidation considered more efficient.But glycolysis follows more universal pathway and basic pathway.