Question

How much ATP does a 6 carbon fatty acid yield with a double bond between carbons 4 and 5? (assume each NADH is equal to 2.5 ATP and every FADH2 is equal to 1.5ATP)

Answer 1

β oxidation has 4 steps snd each's catalyzed by an enzyme. Out of these 4 steps, two steps yield one NADH and FADH2 each. Therefore 2.5+1.5= 4 ATP is produced from a combination of NADH and FADH2. Now, a 6-carbon fatty acid would undergo β oxidation twice and hence generate 4*2 = 8 ATPs.

Now, due to β oxidation, acetyl CoA is produced which when enters the TCA cycle yields 3 NADH (3*2.5=7.5 ATP) and one FADH2 (1.5 ATP) that is 9 ATP molecules.

Now, a 6-carbon fatty acid would undergo β oxidation twice and in turn generate 3 acetyl-CoA equivalents. That is 9*3= 27 ATPs.

Therefore total ATP produced:

ATPs through β oxidation pathway = 8

ATPs from acetyl CoA = 27

ATPs that are required for fatty acid activation = -2

Total ATP = 33 ATPs