Cellular Respiration

[PooyaH]

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Hey guys,

I've read different things in different text books, so I'm gonna write what I know and see if you agree or disagree:

In glycolysis:

Input = 2 ATPs
Output = 2ATPs from 2 ADPs & 6ATPs from 2 NADHs (2ATPs per NADH), Net: 4 ATPs so far

Pyruvate Decarboxylation:

6ATP from 2NADHs (3ATPs per NADH)
Net: 10ATPs so far

Citric Acid Cycle:

18ATPs from 6 NADHs (3ATPs per NADH)
4ATPs from 2 FADH2s (2ATPs per FADH2)
2ATPs from 2 GTPs
Net 36ATPs!!!

Let me know if this is right, I've also read we get 2 ATPs in glycolysis, 2ATPs in pyruvate decarboxylation, and 34ATPs in ETC!

Thanks!

 

[Chga]

its 2.5 atps per NADH
and its 1.5 atps pet FADH2

 

[PooyaH]

its 2.5 atps per NADH
and its 1.5 atps pet FADH2

Where did you get 2.5 and 1.5 ATPs from??? Last time I checked they were 3 and 2 ATPs lol

 

[osimsDDS]

Hey guys,

I've read different things in different text books, so I'm gonna write what I know and see if you agree or disagree:

In glycolysis:

Input = 2 ATPs
Output = 2ATPs from 2 ADPs & 6ATPs from 2 NADHs (2ATPs per NADH), Net: 4 ATPs so far

Pyruvate Decarboxylation:

6ATP from 2NADHs (3ATPs per NADH)
Net: 10ATPs so far

Citric Acid Cycle:

18ATPs from 6 NADHs (3ATPs per NADH)
4ATPs from 2 FADH2s (2ATPs per FADH2)
2ATPs from 2 GTPs
Net 36ATPs!!!

Let me know if this is right, I've also read we get 2 ATPs in glycolysis, 2ATPs in pyruvate decarboxylation, and 34ATPs in ETC!

Thanks!

Glycolysis:
The net ATP production from glycolysis is 2 ATP, also 2 NADH that only make 2 ATP per NADH in Oxydative phosphorylation instead of the regular 3ATP per NADH...
Also 2 pyruvate molecules

Pyruvate decarboxylation:
-1 NADH and 1 CO2 per pyruvate molecule so total 2 NADH and 2 CO2

Krebs:
-For 2 pyruvate molecules you get 2 ATP, 6 NADH, 2 FADH2, and 2 CO2

Oxidative phosphorylation:
-Glycolysis: 2NADH = 4 ATP
-Pyruvate decarboxylation: 2NADH = 6 ATP
-Krebs: 6NADH = 18 ATP, 2 FADH2 = 4 ATP

Total from oxidative phos. = 32 ATP + 2 ATP (glycolysis) + 2 ATP (krebs) = 36 ATP per glucose molecule

 

[osimsDDS]

its 2.5 atps per NADH
and its 1.5 atps pet FADH2

eh dude i wouldnt go with that, they always use 3 per NADH and 2 per FADH2, they never go by the 2.5 and 1.5 rule even though many people have stated otherwise...i will gaurantee you they wont use those on the test....

 

[harrygt]

Pooya jan, regarding glycolysis, I think you had some mistakes there.
The input of glycolysis is 2 ATP, but 4 ATPs are made at the end at the substrate level. Also 2 NADH are made in glycolysis [multiply it by either 2 or 3 based on reference to different sources] (I would still multiply by 3)

This is the part that I did not get, when you said, "Output = 2ATPs from 2 ADPs & 6ATPs from 2 NADHs (2ATPs per NADH), Net: 4 ATPs so far". You are making a mistake here. Review the glycolysis section for sure.

 

[PooyaH]

Pooya jan, regarding glycolysis, I think you had some mistakes there.
The input of glycolysis is 2 ATP, but 4 ATPs are made at the end at the substrate level. Also 2 NADH are made in glycolysis [multiply it by either 2 or 3 based on reference to different sources] (I would still multiply by 3)

This is the part that I did not get, when you said, "Output = 2ATPs from 2 ADPs & 6ATPs from 2 NADHs (2ATPs per NADH), Net: 4 ATPs so far". You are making a mistake here. Review the glycolysis section for sure.

Yeah you're right man, I meant to say 4 ATP 😀, and 2 of them get used up again for the next glycolysis cycle! my bad! lol and we get 4 ATPs from 2 NADHs not 6 ATPs!!! Sorry bro I've been studying since 9am. my brain is fried right now!

 

[ryry]

eh dude i wouldnt go with that, they always use 3 per NADH and 2 per FADH2, they never go by the 2.5 and 1.5 rule even though many people have stated otherwise...i will gaurantee you they wont use those on the test....

its normally 3 ATP per NADH and 2 ATP per FADH2

But two of the NADH produced from Glycolysis, 3 ATPs are produced from each NADH but 1 is used up to transport one NADH into the Mitochondrial matrix - remember, this only applies to Eukaryotes (prokaryotes, there is no need to transfer NADH across a membrane because they lack membrane-bound organelles.) hence, 2 ATP per NADH from GLYCOLYSIS in Eukaryotes

If we recalculate everything:

glycolysis - 2 ATP + 2 NADH
Decarboxylation - 1 NADH x 2 (1 per pyruvate, therefore 2 per glucose)
Citric Acid Cycle - (3 NADH + 1 FADH2 + 1 ATP) x 2

By the time we get to ETC/Oxd. Phosphorylation, the number of NADH is:

2 NADH from Glycolysis + 2 NADH from Decarboxylation + 6 NADH from Krebs Cycle

2 NADH from Glycolysis - 2 x 2 = 4 ATP
8 NADH from Decarb + Krebs = 8 x 3 = 24 ATP
2 FADH2 from Krebs = 2 x 2 = 4 ATP

Subtotal: 32

Now we add in the rest of ATP produced w/o using NADH

2 ATP from Glycolysis + 2 ATP from 2 GTP in Krebs + 32 ATP = 36 ATP!!!

If prokaryote, it would be 38 because, for the reasons stated above.

Hope this helps!

 

[hdu]

There is a convention followed by some books that say that:

1 mol of NADH.H+ when oxidized in the respiratory chain,, release energy enough for the synthesis of 3 moles of ATP, while 1 mol of FADH2, when oxidized in the respiratory chain, release energy enough for the synthesis of 2 moles of ATP.

Other books say that it is most accurate to say that 1 mol of NADH.H+ when oxidized in the respiratory chain, release energy enough for the synthesis of 2.5 moles of ATP, while 1 mol of FADH2, when oxidized, release energy enough for the synthesis of 1.5 moles of ATP

It is not about who is right of who is wrong, but about which is the convention that is used in your textbook or in your Biochemistry course,

Anyway, review the calculations of the first post:

glucose to pyruvate

- 2ATP, +2ATP, + 2 NADH.H+ (produced in the cytosol)

2 Pyruvate to 2 acetyl CoA (decarboxylation that occurs in mitochondria)

2 NADH.H+

2 acetyl Co A in Krebs cycle (mitochondria)

2x (1GTP, + 3NADH.H+ + 1FADH2)


My blog: www.biochemistryquestions.wordpress.com

 

[hdu]

Ryry, I think you have explained it very well.

I just would like to add that there are two different shuttles in eucaryotes that transport the Hydrogens from NADH.H+ produced in the cytosol (like the two in glycolysis) to the mitochondria.
One of then is the malate-aspartate shuttle. Using this shuttle, the Hydrogens that come from the cytoplasmatic NADH.H+ are taken by other molecules of NAD+ inside the mitochondria, so there is not "waste" of ATP, since you obtain again NADH.H+ inside the mitochondria. When used this shuttle, the energetic balance of glycolysis up to CO2 and water is 38 ATP.

The other shutlle is the glycerophosphate shuttle. In this shuttle, the Hydrogens from NADH.H+ produced in the cytosol are taken by FADH2 in the mitochondria, and so they yield only 2 ATP. In this case, the energetic balance of glycolysis up to CO2 and water is 36 ATP.

It explains that in books that use the same convention (3ATP for each NADH.H+ oxidized and 2 ATP for each FADH2 oxidized), sometimes you find a glycolysis net production of 36 ATP while others show 38 ATP. In fact, it depends in which shuttle is used to enter the Hydrogens of the NADH.H+ from the cytosol to the mitochondria.

 

[PooyaH]

Ryry, I think you have explained it very well.

I just would like to add that there are two different shuttles in eucaryotes that transport the Hydrogens from NADH.H+ produced in the cytosol (like the two in glycolysis) to the mitochondria.
One of then is the malate-aspartate shuttle. Using this shuttle, the Hydrogens that come from the cytoplasmatic NADH.H+ are taken by other molecules of NAD+ inside the mitochondria, so there is not "waste" of ATP, since you obtain again NADH.H+ inside the mitochondria. When used this shuttle, the energetic balance of glycolysis up to CO2 and water is 38 ATP.

The other shutlle is the glycerophosphate shuttle. In this shuttle, the Hydrogens from NADH.H+ produced in the cytosol are taken by FADH2 in the mitochondria, and so they yield only 2 ATP. In this case, the energetic balance of glycolysis up to CO2 and water is 36 ATP.

It explains that in books that use the same convention (3ATP for each NADH.H+ oxidized and 2 ATP for each FADH2 oxidized), sometimes you find a glycolysis net production of 36 ATP while others show 38 ATP. In fact, it depends in which shuttle is used to enter the Hydrogens of the NADH.H+ from the cytosol to the mitochondria.

Sooo do we have to know every step of glycolysis or Krebs cycle for the DAT?

 

[hdu]

Sorry, I do not know about that. Maybe I am giving too much detail, but I think it is important to understand why sometimes you find different numbers in different books, and do not waste time finding who is right and who is wrong.

 

[ryry]

Sooo do we have to know every step of glycolysis or Krebs cycle for the DAT?

i've taken about 8 practice tests so far, and what i realized was that they typically ask about

How many ATPs generated total/one specific step?
Where does each step occur?

So i would just memorize basically what i wrote to you above. i checked with the books so they are correct. hope it helps.

 

[PooyaH]

i've taken about 8 practice tests so far, and what i realized was that they typically ask about

How many ATPs generated total/one specific step?
Where does each step occur?

So i would just memorize basically what i wrote to you above. i checked with the books so they are correct. hope it helps.

Sweet...Thanks!

 

[Chga]

I am going to quote streetwolf from couple of months ago


"2.5 and 1.5 are the correct and current accepted values in most literature. 2 and 3 are old and not correct anymore haha.

You get 2 NADH net from glycolysis and 2 net ATP = 7 ATP total. However, the 2 NADH are unable to be transported into the mitochondria for oxidative phosphorylation. They must be shipped in as FADH2 and thus only count as 1.5 ATP each = 5 ATP total for glycolysis.

The PDH complex (pyruvate decarboxylation in the mitochondria) yields 2 NADH = 5 ATP.

The TCA cycle yields 3 NADH and 1 FADH2 per turn, plus 1 GTP per turn x 2 turns = 6 NADH (15 ATP), 2 FADH2 (3 ATP), and 2 GTP (2 ATP) = 20 ATP.

Total = 5 + 5 + 20 = 30 ATP in eukaryotes.

In prokaryotes it would be 32 ATP because they do not lose the 2 ATP it takes to shuttle NADH from glycolysis into the mitochondria. Of course this is because they don't have mitochondria."
If you want to read the full thread here the link
http://forums.studentdoctor.net/showthread.php?t=479294

yes im really confused and I will began to read the chapter in a few minutes.