ATP yield from substrate phosphorylation

[AntonFreeman]

Net ATP from glycolysis is 2 ATP and from substrate phosphorylation is 4 ATP correct? also does substrate phosphorylation happen in aerobic state or anaerobic state? pyruvate would not enter TCA without O2 right?

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[BB8730]

I think you're getting terms confused. Substrate-level phosphorylation happens during glycolysis and produces 2 ATP per glucose molecule. It can happen aerobically or anaerobically.

The TCA cycle generates 4 NADH, 1 GTP(=ATP), and 1 FADH2 per pyruvate. The ETC, aka oxidative phosphorylation, generates ATP from the NADH and FADH2 from glycolysis and TCA cycle.

The TCA and ETC only happen under aerobic conditions. Under anaerobic conditions, the pyruvate from glycolysis would be converted to lactate to regenerate NAD+. Not sure where you're getting the 4 ATP from.

 

[sciencebooks]

Net ATP from glycolysis is 2 ATP and from substrate phosphorylation is 4 ATP correct? also does substrate phosphorylation happen in aerobic state or anaerobic state? pyruvate would not enter TCA without O2 right?

Yes.

Net ATP per glycolysis = 2 ATP
Net ATP per Kreb's = 2 ATP (1 ATP -- from GTP -- per spin; 2 pyruvates --> 2 acetyl coA --> 2 spins)
Net ATP from substrate level phosphorylation = 2+2 = 4 ATP

Yes and no, I guess. Substrate level phosphorylation is glycolysis AND Kreb's cycle. Glycolysis can happen anaerobically but Kreb's cycle cannot so the entire process cannot occur.

And yes. It would not because Kreb's cycle requires O2 indirectly.

 

[sciencebooks]

I think you're getting terms confused. Substrate-level phosphorylation happens during glycolysis and produces 2 ATP per glucose molecule. It can happen aerobically or anaerobically.

The TCA cycle generates 4 NADH, 1 GTP(=ATP), and 1 FADH2 per pyruvate. The ETC, aka oxidative phosphorylation, generates ATP from the NADH and FADH2 from glycolysis and TCA cycle.

The TCA and ETC only happen under aerobic conditions. Under anaerobic conditions, the pyruvate from glycolysis would be converted to lactate to regenerate NAD+. Not sure where you're getting the 4 ATP from.

I was taught that it is both glycolysis AND Kreb's cycle. I think OP is getting at that too.

 

[BB8730]

Yes.

Net ATP per glycolysis = 2 ATP
Net ATP per Kreb's = 2 ATP (1 ATP -- from GTP -- per spin; 2 pyruvates --> 2 acetyl coA --> 2 spins)
Net ATP from substrate level phosphorylation = 2+2 = 4 ATP

Yes and no, I guess. Substrate level phosphorylation is glycolysis AND Kreb's cycle. Glycolysis can happen anaerobically but Kreb's cycle cannot so the entire process cannot occur.

And yes. It would not because Kreb's cycle requires O2 indirectly.

I was taught that it is both glycolysis AND Kreb's cycle. I think OP is getting at that too.

Ah yes I suppose the GTP creation in the TCA cycle is also substrate-level phosphorylation. It is definitely different from glycolysis though because the ATP is stuck in the mito and it takes energy to get it out, so you don't get 4 net (cytoplasmic) ATP from both processes. I think that's a bit beyond the scope of the MCAT but that's why I see them as being very different.

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[MedPR]

TCA and Glycolysis both produce ATP via substrate-level phosphorylation.
ETC is oxidation phosphorylation.