Glycolysis/Cell Respiration

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I found this chart searching the forums and am trying to understand a part of it:

http://imgur.com/k0QVH

Why is the ATP equivalence of the NADH different for glycolysis than the equivalence for the other two steps?

Originally Posted by Anonymous01

I found this chart searching the forums and am trying to understand a part of it:

http://imgur.com/k0QVH

Why is the ATP equivalence of the NADH different for glycolysis than the equivalence for the other two steps?

Because the cell has to spend energy importing NADH and pyruvate into the mitochondria innter matrix so there is less net energy per molecule. See glycerol phosphate shuttling. The NADH produced in krebs cycle on the other hand is produced within mito so no import is necessary.

Thanks for the reply!

The ExamCrackers book says, "each NADH (depending upon the mechanism used for transport) may or may not require the hydrolysis of ATP." They were vague about it, but your explanation cleared it up.

Thanks again!

Just want to make sure that the net 36 ATP is per glucose, right? So the kreb's cycle only produces ~18ATP per cycle, since 1 glucose = 2 turns due to 2 pyruvates produced by glycolysis = 2 acetyl CoA's to enter into Kreb's?

i think less. that figure shows 18 per glucose. so half per cycle, 9. then we count 1 GTP and 1 FADH2.

I think it's 12.

Glycolysis gets you 2+4 ATP per glucose. The other 30 come from the rest of the respiration process where each step turns twice per a glucose molecule. That means that you get 6 ATP from converting NADH during entering Kerb's cycle twice which leaves you 24 for the Kerb's cycle itself or 12 for each turn.

Depending on the literature the 36 number will vary somewhere around 32-36. You also get 2 more ATPs in prokaryotes since you lose 2 of them to cross the mitochondrial membrane in eukaryotes.

It is 29 net ATP per glucose, not 36, according to new research, not sure if the MCAT will reflect this discovery or not.

Originally Posted by Perimeter

It is 29 net ATP per glucose, not 36, according to new research, not sure if the MCAT will reflect this discovery or not.

I doubt you would need to worry about it, since the MCAT isn't going to ask a question about something that has so many different published numbers, or if it does it will either give you the number to assume, or give a series of options, only one of which makes any sense.

One aspect relevant about this question is actually how this manifests between prokaryotes and eukaryotes. Prokaryotes actually produce more ATP per glucose molecule--because prokaryotes don't have to expend energy to shuttle pyruvates into mitochondria.

It is very unlikely that you would be asked a question about how many net ATPs are created when something happens. You'll be given that in a passage