Sterate Oxidation. Sterate is a 18-carbon saturated fatty acid (C18 H36 O2) that

Question

Sterate Oxidation. Sterate is a 18-carbon saturated fatty acid (C18
H36
O2) that
can be oxidized completely to carbon dioxide and water by a combination of
ß-oxidation and the TCA cycle.


a) Calculate the net number of ATP molecules generated by the complete
catabolism to sterate to the two-carbon (acetyl CoA) level. (Be sure to
remember the ATP that is used in the initial activation of the fatty acid in
reaction FA-10).
b) Next, calculate the number of ATP molecules generated by the further
oxidation of the eight resulting acetyl-CoA molecules to carbon dioxide and
water.

Explanation / Answer

- oxidation of fatty acids will produce one NADH + H+ and one FADH2 for every one acetyl CoA molecule released from the chain. 1 Acetyl CoA = 1 NADH + H+ + 1 FADH2 In the case of stearic acid which is an 18 carbon chain, gives off 9 acetyl CoA. But the number of energy molecules released will be for 8 acetyl CoA. Because the last molecule is left alone. So, for -oxidation of stearic acid the number of energy molecules are 8  NADH + H+ and 8 FADH2 That equals to - 8NADH + H+ x 3 = 21 ATP - 8 FADH2 x 2 = 16 ATP The acetyl CoA molecules will enter the citric acid cycle, producing energy molecules, of 3NADH + H+ , 1 GTP and 2 FADH2 for one Acetyl CoA molecule. Therefore for 9 acetyl CoA molecules the total number of energy molecules are 27 NADH + H+ = 81 ATP 18 FADH2 = 36 ATP 9 GTP = 9 ATP Therefore, the total number of ATP molecules are 21 +16+ 81 + 36 + 9 = 163 ATP 2ATP are utilized at the starting of -oxidation. Therefore the net ATP released are 161 ATP.

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