Oxidative vs. Substrate-Level Phosphorylation

[MNova]

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Hey guys,

I've always learned that there are 32 ATP generated via oxidative phosphorylation and 4 ATP generated via substrate-level phosphorylation. This is also how Kaplan teaches it and presents it in their material, as well as what the Bio book I use says.

However, on TopScore (the question wasn't directly asking about the above), one of the explanations gave some background info on cell respiration, and it says that 34 are generated during oxidative phosphorylation and 2 during substrate-level.

I know that the discrepancy is based on when the ATPs that need to be subtracted are actually subtracted, but I was wondering if you guys knew what the generally accepted values to use are.

(I've been saying 2 ATP during glycolysis, 2 ATP during Krebs = 4 ATP for substrate-level; 2 NADH from glycolysis are worth 2 ATPs each, the remaining 8 NADHs (2 from pyruvate decarboxylation, 6 from Krebs) are worth 3 ATPs each, and the 2 FADH2s from Krebs are worth 2 each = 32 ATPs from oxidative phosphorylation).

Thanks for all of your help everyone 🙂

 

[jay47]

I think that your explanation, the one in parentheses) is perfectly correct, so 32 ATP from oxidative phosphorylation, and 4 from substrate level. Although the "ATP" created from the Krebs is actually a GTP, which is an ATP equivalent.

In addition, if you have taken Biochem, then you'll know that the number of ATP per NADH and FADH2 is actually not a whole number because of the number of H+ moved into the intermembrane space. Don't worry about this though... I would just go with the explanation you said in parentheses, this is what most entry level bio books would say.

 

[Shinpe]

The only thing that crosses my mind is that question could have been for prokaryotes. What you explained is correct for Eukaryotes, but in Prokaryotes, the 2 NADH produced in glycolysis still produce 3 NADH each because they don't have to pass through the mitochondrial membrane. SO they get 34 (oxidate) + 4 (substrate). = 38 total ATP.

 

[nze82]

In case of prokaryotes, this number changes to 38, because the NADH produced during glycolysis is equivalent to 3 ATP molecules in case of these organisms (as oppose to 2 ATP molecules in case of eukaryotes).

 

[joonkimdds]

(I've been saying 2 ATP during glycolysis, 2 ATP during Krebs = 4 ATP for substrate-level; 2 NADH from glycolysis are worth 2 ATPs each, the remaining 8 NADHs (2 from pyruvate decarboxylation, 6 from Krebs) are worth 3 ATPs each, and the 2 FADH2s from Krebs are worth 2 each = 32 ATPs from oxidative phosphorylation).

Thanks for all of your help everyone 🙂

This is correct.