NADH, pyruvate and acetyl CoA

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Kap
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NADH, pyruvate and acetyl CoA

Post by Kap » Sat Dec 10, 2005 11:44 pm

I've got a question about the conversion of pyruvate to acetyl CoA, the linkage from the glycolisis to the cirtic acid cycle. In this step it is said an enzym transfers electrons to NAD+, so it can become NADH. If I understand this right, the NAD+ receives electrons from the pyruvate, but where does it get its H+ ions from, to become NADH? Acetyl CoA contains as much hydrogen as pyruvate, isn't it?

Dennis

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Post by sdekivit » Sun Dec 11, 2005 10:45 am

It does get its H from pyruvate

--> the type of oxidation is: HCOH --> C=O + 2H(+) + 2e(-)

--> NAD(+) takes up 2 electrons and 1 H to form NADH + H(+)

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Post by Kap » Sun Dec 11, 2005 2:03 pm

Thank you for trying to help me out. But after studying some books I am still not completely satisfied...

In the 7th edition of campbells' biology (page 168, figure 9.10) they show a figure, which I tried to reconstruct here:

(-)OOC-CO-CH3 -->CoA-S-CO-CH3 with foming of NADH + H(+) out of NAD(+), lose of CO2 and work of Coenzyme A.

And it seemed to me as if two H's needed here for NADH and H(+) are created there out of nothing. That's why I asked my question. So I searched in some other books and I found one which is saying the following:

HOOC-CO-CH3 + HS-CoA --> CoA-S-CO-CH3 (Also with lose of CO2 and forming of NADH)

And in this equation it looks like as if the first H needed is coming from pyruvate, and the second one from the HS attached to CoA. Is there something I see completely wrong here?

It's just my first year of biology, and it is possible I'm not aware of more complexicity than there so far has been told in those books or it may be I just don't understand anything about this...

Thank you in advance.

Dennis

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Post by Kap » Sun Dec 11, 2005 3:22 pm

There are two pyruvates created at the end of the glycolisis... :shock: I think that's why I didn't see where that second H(+) came from... But I'm still curious about the H at the CoA.

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Post by sdekivit » Mon Dec 12, 2005 11:13 am

Kap wrote:There are two pyruvates created at the end of the glycolisis... :shock: I think that's why I didn't see where that second H(+) came from... But I'm still curious about the H at the CoA.


see my reaction equation

--> 2 Hs are taken off the substrate and are tranferred to the cytosol and NAD(+).

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