Formation of water in degradation of glucose

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10+ Year Member
Aug 24, 2008
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balance equation for degradation of glucose is

1 glucose + 6O2 --> 6CO2 + 6H2O

I can't find where all the water are coming from
I know there are 2H20 from glycolysis

so 4 must be coming from the electron transport chain

I guess my question is when NADH donates the electron that goes through the chain how many NADH does it take to produce the rest of the 4 molecules of H20 ?

I just know that 1/2 O2 is reduced to water at the end of etc but as far how that whole scheme produce 4 molecules of water with about 20 NADH entering the chain is confusing to me. :rolleyes:

anybody care to enlighten me?


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Jun 6, 2008
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I don't know if I completely understand what you are saying, but I will try.

Firstly, NADH don't "enter" the cycle, they are products, thus they leave the cycle. NAD+, on the other hand, enter the cycle.

I'm not too sure why you think 20 NADH leave the cycle... Its been a while since Ive looked at glycolysis and the CAC, but I think I remember the end product being 20something ATPs are produced, where each NADH produces 2-3 ATP...

It sounds like you know where 4 of the waters are coming from: the NADH. I can't confirm if this is right, but I'm pretty sure a water is also produced in the formation of PEP (phosphoenolpyruvate) the precursor to pyruvate, thus there are 2 produced here.. 4+2 = 6 per glucose molecule.

Water is not really important in this process. But it's good that you are trying to understand everything...

Do you want to rephrase your question?