discrepancy between TPR and EK in cellular respiration?

[capn jazz]

Okay. This question totally threw me off and maybe someone who has the TPR Bio review can shed some light on it, because it's from the TPR Science Workbook, passage 17 of biology.

If E. coli is incubated under aerobic conditions, how many molecules of ATP would be produced upon the complete oxidation of one molecule of glucose?

a) 28
b) 30
c) 32
d) 34

The answer is apparently C: 32. Here's the explanation:
The complete oxidation of glucose yields 2 ATP and 2 NADH through glycolysis, 2 GTP in the Krebs cycle (equivalent to ATP in energy), 2 NADH from pyruvate dehydrogenase, 2 FADH2 from the Krebs Cycle and 6 NADH from the Krebs Cycle. In oxidative phosphorylation, each NADH yields 2.5 ATP and each FADH2 yields 1.5 ATP. This all totals up to 32 ATP per glucose. (In eukaryotes, the answer is 30 ATP per glucose due to the fact that electrons from the glycolytic NADH [in the cytoplasm] must be shuttled to the electron transport chain [in the mitochondria]; they bypass the first proton pump, just like FADH2, and yield only 1.5 ATP, just like FADH2.)

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Now, honestly, is TPR on crack?? I have NEVER heard of eukaryotic glycolysis producing 30 ATP. I have also never heard of NADH producing 2.5 ATP and FADH2 producing 1.5, always 3 and 2, respectively. I understand the 2 different shuttle systems for getting cytosolic NADH into the matrix resulting in 2 ATP per NADH instead of 3 (although the malate-aspartate shuttle results in 3 ATP per NADH).

But 30 for eukaryotes and 32 for prokaryotes??? Someone please make sense of this. I know 36/38 is the "theoretical yield" but I thought all we needed to know is the theoretical yield.

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[Bernoull]

Okay. This question totally threw me off and maybe someone who has the TPR Bio review can shed some light on it, because it's from the TPR Science Workbook, passage 17 of biology.

If E. coli is incubated under aerobic conditions, how many molecules of ATP would be produced upon the complete oxidation of one molecule of glucose?

a) 28
b) 30
c) 32
d) 34

The answer is apparently C: 32. Here's the explanation:
The complete oxidation of glucose yields 2 ATP and 2 NADH through glycolysis, 2 GTP in the Krebs cycle (equivalent to ATP in energy), 2 NADH from pyruvate dehydrogenase, 2 FADH2 from the Krebs Cycle and 6 NADH from the Krebs Cycle. In oxidative phosphorylation, each NADH yields 2.5 ATP and each FADH2 yields 1.5 ATP. This all totals up to 32 ATP per glucose. (In eukaryotes, the answer is 30 ATP per glucose due to the fact that electrons from the glycolytic NADH [in the cytoplasm] must be shuttled to the electron transport chain [in the mitochondria]; they bypass the first proton pump, just like FADH2, and yield only 1.5 ATP, just like FADH2.)

------

Now, honestly, is TPR on crack?? I have NEVER heard of eukaryotic glycolysis producing 30 ATP. I have also never heard of NADH producing 2.5 ATP and FADH2 producing 1.5, always 3 and 2, respectively. I understand the 2 different shuttle systems for getting cytosolic NADH into the matrix resulting in 2 ATP per NADH instead of 3 (although the malate-aspartate shuttle results in 3 ATP per NADH).

But 30 for eukaryotes and 32 for prokaryotes??? Someone please make sense of this. I know 36/38 is the "theoretical yield" but I thought all we needed to know is the theoretical yield.

To add to ur heartburn, I referenced my bio textbook(Life, Purves et al,7e; pg 140) and guess what, it's 36 NET ATP!!!!!! Clearly, getting a precise consistent answer is like taking the census . Back in my college days I was taught 36 too. 2 net from glycolysis, 2 net from TCA and 32 from ETC. I have EK and they SAY:

"You should know that aerobic respiration
produces about 36 net ATPs (includes
glycolysis). You should also know that 1
NADH brings back 2 to 3 ATPs and that
1 FADH, brings back about 2 ATPs. "

In AO they also say that some books say 2.5ATP/NAdh and 1.5ATP/Fadh2 but student should use 36 unless the MCAT says otherwise.

(In eukaryotes, the answer is 30 ATP per glucose due to the fact that electrons from the glycolytic NADH [in the cytoplasm] must be shuttled to the electron transport chain [in the mitochondria]; they bypass the first proton pump, just like FADH2, and yield only 1.5 ATP, just like FADH2.)

I remember reading somewhere about this inefficiency and that cardiac muscles produce more ATP/glucose molecule because they transfer either electrons or coenzymes more efficiently...

 

[BloodySurgeon]

It was originally believed that 1 NADH = 3 ATP and 1 FADH2 = 2 ATP. It is now inaccurate and is currently believed that 1 NADH = 2.5 ATP and 1 FADH2 = 1.5 ATP.

The older model would have Eukaryotes producing 36 ATP per Glucose molecule, Bacteria producing 38 ATP per Glucose molecule whereas the newer model has Eukaryotes producing 30 ATP per Glucose versus Bacteria's 32 ATP per Glucose molecule. For the MCAT sake, they will not give you both answer choices unless the model is clearly explained in the passage.

 

[capn jazz]

I can accept that, but I haven't read that before anywhere so I have no idea how I was supposed to know that.

 

[vickpick]

To add to ur heartburn, I referenced my bio textbook(Life, Purves et al,7e; pg 140) and guess what, it's 36 NET ATP!!!!!! Clearly, getting a precise consistent answer is like taking the census . Back in my college days I was taught 36 too. 2 net from glycolysis, 2 net from TCA and 32 from ETC. I have EK and they SAY:

"You should know that aerobic respiration
produces about 36 net ATPs (includes
glycolysis). You should also know that 1
NADH brings back 2 to 3 ATPs and that
1 FADH, brings back about 2 ATPs. "

In AO they also say that some books say 2.5ATP/NAdh and 1.5ATP/Fadh2 but student should use 36 unless the MCAT says otherwise.

(In eukaryotes, the answer is 30 ATP per glucose due to the fact that electrons from the glycolytic NADH [in the cytoplasm] must be shuttled to the electron transport chain [in the mitochondria]; they bypass the first proton pump, just like FADH2, and yield only 1.5 ATP, just like FADH2.)

I remember reading somewhere about this inefficiency and that cardiac muscles produce more ATP/glucose molecule because they transfer either electrons or coenzymes more efficiently...

the 36 is net ATP production in a 100% efficient human or bacterial cell..

since there is a problem with membrane leakage, 32 is the most widely use number in terms of ATP production by cells..

1 more problem for less production of ATP on average is that many times NADH is used for other function other than the ETC..