Anaerobic Respiration question?

[predental89]

Hey guys,

I had a quick question regarding anaerobic respiration, I know that O2 is needed for ETC as the final electron acceptor and w/out it NADH and FADH2 would accumulate and stop glycolysis and krebs. Now, with anaerobic respiration we have lactate and alcohol fermentation to generate NAD+ which helps glycolysis and krebs continue, but if O2 is absent still then what good is it that we can make NADH and FADH2 again? because even if they go through ETC there is no O2 to take the electrons at the end of the chain and make water. I hope this makes sense? Please any help would be appreciated

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[flin5845]

Hey guys,

I had a quick question regarding anaerobic respiration, I know that O2 is needed for ETC as the final electron acceptor and w/out it NADH and FADH2 would accumulate and stop glycolysis and krebs. Now, with anaerobic respiration we have lactate and alcohol fermentation to generate NAD+ which helps glycolysis and krebs continue, but if O2 is absent still then what good is it that we can make NADH and FADH2 again? because even if they go through ETC there is no O2 to take the electrons at the end of the chain and make water. I hope this makes sense? Please any help would be appreciated

remember that you still generate a small amount of ATP through substrate level phosphorylation. Even though it is not much....it is still something.

 

[predental89]

remember that you still generate a small amount of ATP through substrate level phosphorylation. Even though it is not much....it is still something.

I know that but if we are in ANAEROBIC respiration and we have this newly generated NAD+ to go through glycolysis and krebs to make NADH, if it goes through ETC, we still dont have O2 to accept the electrons at the end of the chain? I don't get it :/

 

[LetsGo2DSchool]

The NADH made in Glycolysis is the same NADH that is broken down to NAD+ in fermentation. So it continuously cycles (Glycolysis ---> Fermentation ---> Glycolysis ---> Fermentation ---> etc.) or NADH ---> NAD+ ---> NADH ---> NAD+ ---> etc. Remember, Glycolysis and Fermentation both occur in the cytoplasm. Thus, the NADH produced in glycolysis won't be shuttled to the mitochondria and get backed up.

FADH is made in Krebs Cycle so besides the few FADH that will get backed up once oxygen is unavailable, this process shuts down once the anaerobic path kicks in. Thus FADH won't keep being made.

 

[predental89]

The NADH made in Glycolysis is the same NADH that is broken down to NAD+ in fermentation. So it continuously cycles (Glycolysis ---> Fermentation ---> Glycolysis ---> Fermentation ---> etc.) or NADH ---> NAD+ ---> NADH ---> NAD+ ---> etc. Remember, Glycolysis and Fermentation both occur in the cytoplasm. Thus, the NADH produced in glycolysis won't be shuttled to the mitochondria and get backed up.

FADH is made in Krebs Cycle so besides the few FADH that will get backed up once oxygen is unavailable, this process shuts down once the anaerobic path kicks in. Thus FADH won't keep being made.

Ohhh ok this is starting to make sense, I was thinking about it wrong. Thank you

 

[LetsGo2DSchool]

No problem man. Cell metabolism is my bread and butter in biology. If you have any more questions in this area, I could probably answer them.

 

[predental89]

I appreciate it, I will let you know if anything else comes up!

 

[LetsGo2DSchool]

Here's another thing about cell respiration that most people don't understand...

The difference between the total ATP production (36 ATP in eukaryotes vs. 38 ATP in prokaryotes) is due to the energy required to transport the 2 NADH produced in glycolysis to the mitochondria.

Thus, due to this energy expenditure in eukaryotes, each NADH made in glycolysis yields a net 2 ATPs whereas the NADH made in Krebs Cycle yield 3 ATPs.

However, in prokaryotes, cell respiration occurs at the cell membrane and thus there is no mitochondria to transport the NADH made in glycolysis and thus, every NADH will yield 3 ATPs.

 

[redkbro]

Here's another thing about cell respiration that most people don't understand...

The difference between the total ATP production (36 ATP in eukaryotes vs. 38 ATP in prokaryotes) is due to the energy required to transport the 2 NADH produced in glycolysis to the mitochondria.

Thus, due to this energy expenditure in eukaryotes, each NADH made in glycolysis yields a net 2 ATPs whereas the NADH made in Krebs Cycle yield 3 ATPs.

However, in prokaryotes, cell respiration occurs at the cell membrane and thus there is no mitochondria to transport the NADH made in glycolysis and thus, every NADH will yield 3 ATPs.

A HA! i remembered reading the reason for that in my cell book last year, but have been to lazy to look it up. thanks for the info!

 

[thejamespark]

No problem man. Cell metabolism is my bread and butter in biology. If you have any more questions in this area, I could probably answer them.

So does anaerobic respiration PRODUCE ATP?
I mean in glycolysis, it produces net of 2 ATP but if a questions asking, which one of these produces ATP?
does anaerobic respiration count as one of the answers because it is counting glycolysis as one of the steps in anaerobic resp?

 

[journeybegins]

Anaerobic respiration definitely produces ATP, just a lot less than aerobic respiration. Glycolysis can occur with or without O2, but produces less ATP since it uses substrate-level phosphorylation. Whereas, the ETC uses oxidative phosphorylation and makes the most ATP.

Whenever you see anaerobic respiration, think no O2.
3 processes can go without O2.
1) Glycolysis --> uses substrate-level phosphorylation produces a net of 2 ATP, 2 NADH, 2 pyruvate
2) Fermentation (in yeasts) --> pyruvate goes on to produces ethanol + NAD+ needed to keep Glycolysis going
3) Lactate fermentation (in muscles) --> pyruvate goes on to make lactic acid build up in the muscles + NAD+ to keep Glycolysis going

Aerobic respiration processes that need O2
1) Krebs -- uses substrate-level phosphorylation
2) ETC -- uses oxidative phosphorylation