Question

Imagine that you've just discovered a new microbe with an ATP synthase that is very efficient. As such, it takes only 2 H+ to make 3 ATP molecules. Now you want to know-how many ATP molecules will this organism produce when it completely oxidizes 1 molecule of glucose? Assume that 10 protons are pumped across the inner membrane for every NADH molecule, while 6 protons are pumped for every FADH2. How many ATP molecules would this organism produce when it completely oxidizes 1, C18 fatty acid (18:0)?

Answer 1

One molecule glucose is oxidized to two molecules of pyruvate produces 2ATP and 2NADH.

Oxidation of pyruvate to acetyl Co-A produces one NADH. So two NADH from two pyruvates.

Acetyl Co-A is completely oxidized to CO2 through the TCA cycle and 3 NADH, 1 FADH, and 1 GTP are produced.

So overall 6 NADH, 2 FADH, and 2 ATP are produced from on glucose molecules through the TCA cycle.

overall NADH = 2 + 2 +6 = 10

Overall FADH = 2

Overall ATP = 2+2 = 4.

One NADH transport 10 protons and two protons give 3 ATP. So 10 proton give 15 ATP

One FADH transport 6 protons and two protons give 3 ATP. So 6 proton give 9 ATP

10 NADH gives 150*10 = 150 ATP.

2 FADH gives 9*2 = 18 ATP.

So, overall ATP from one glucose molecules = 150 + 18+ 4 =172.

Conversion of fatty acid into fatty acyl Co-A required two ATP. This fatty acyl Co-A is then entered Beta-oxidation.

In one cycle of beta-oxidation one NADH and one FADH are synthesized and the fatty acid losses two carbon during beta-oxidation which are converted into acetyl Co-A. If the fatty acid is 18 carbon, then it undergoes seven beta-oxidation reactions and produces seven acetyl Co-A. The last cycle which has four carbon produces two acetyl Co-A and one NADH and one FADH.

Acetyl Co-A is completely oxidized to CO2 through the TCA cycle and 3 NADH, 1 FADH, and 1 GTP are produced.

From 9 Acetyl Co-A 9*3 NADH, 9 FADH and 9 ATP are synthesized

overall NADH = 9 * 3 + 8 = 27+8 =35

Overall FADH = 9+8 =17

ATP from TCA cycle = 9

One NADH transport 10 protons and two protons give 3 ATP. So 10 proton give 15 ATP

One FADH transport 6 protons and two protons give 3 ATP. So 6 proton give 9 ATP

ATP from NADH = 35 * 15 =525

ATP from FADH = 17 * 9 = 153

Overall ATP = 525+153 +9 = 697.

Two ATP are used to activate fatty acid.

So, overall ATP will be 697 -2 = 695.