Fermentation

[dshnay]

Hi everyone,

I'm a little bit confused with fermentation, does this process include glycolisis (EK states that it does) or is it just a seperate process?

Thanks

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[Vihsadas]

This is really just an issue of nomenclature, but yes, whenever I've heard it brought up glycolysis is included as a part of fermentation. I think that the Kaplan book might even say that. Here's the rationale:

For Glycolysis you need two NAD+ to create any ATP. This is because the step from GAP <==> 1,3-BPG requires one NAD+ and one Pi, and, this reaction happens twice for one glucose molecule. This step also occurs before either of the two ATP producing steps. Thus, you need those two NAD+ to produce any ATP.

Now in fermentation, we have:
Pyruvate <==> Ethanol (or Lactic Acid) with NADH -> NAD+ as a co-reaction. The fermentation step is absolutely required in anaerobic conditions for glycolysis to continue because it regenerates that NAD+ that is needed during the GAP <==> 1,3-BPG stage. Thus, fermentation is thought of as the entire process of Glycolysis through to lactate or ethanol creation.

 

[coffeebythelake]

This is really just an issue of nomenclature, but yes, whenever I've heard it brought up glycolysis is included as a part of fermentation. I think that the Kaplan book might even say that. Here's the rationale:

For Glycolysis you need two NAD+ to create any ATP. This is because the step from GAP <==> 1,3-BPG requires one NAD+ and one Pi, and, this reaction happens twice for one glucose molecule. This step also occurs before either of the two ATP producing steps. Thus, you need those two NAD+ to produce any ATP.

Now in fermentation, we have:
Pyruvate <==> Ethanol (or Lactic Acid) with NADH -> NAD+ as a co-reaction. The fermentation step is absolutely required in anaerobic conditions for glycolysis to continue because it regenerates that NAD+ that is needed during the GAP <==> 1,3-BPG stage. Thus, fermentation is thought of as the entire process of Glycolysis through to lactate or ethanol creation.

Just want to note that pyruvate -> lactate is not considered fermentation, but an equivalent reaction called anaerobic respiration that takes place in body tissues under anaerobic exertion. Both regenerate NAD+, but only fermentation spends carbons.

 

[Vihsadas]

Just want to note that pyruvate -> lactate is not considered fermentation, but an equivalent reaction called anaerobic respiration that takes place in body tissues under anaerobic exertion. Both regenerate NAD+, but only fermentation spends carbons.

Ah okay, good to know. I didn't really think about that, but you are right.

 

[iA-MD2013]

actually, lactic acid is fermentation (ie lactic acid fermentation). Fermentation is simply the process in which pyruvate is reduced (whether to ethanol or lactic acid) to regenerate NAD+. and i dont know how much nomenclature really matters, but anaerobic respiration includes both glycolosis and fermentation.

 

[Vihsadas]

actually, lactic acid is fermentation (ie lactic acid fermentation). Fermentation is simply the process in which pyruvate is reduced (whether to ethanol or lactic acid) to regenerate NAD+. and i dont know how much nomenclature really matters, but anaerobic respiration includes both glycolosis and fermentation.

Yeah exactly. It is just nomenclature at this point. I just e-mailed both of my biochem profs and they disagreed on this point. haha. To the OP: I'd just go by whatever it says in the Kaplan or Princeton book.

 

[iA-MD2013]

haha i hate the nomenclature part of it because every book says something different. theres even differences in the kaplan and princeton books. i dont know...im just gonna follow the bio books and what they taught us in biochem classes. thanks for the clarification vihsadas