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Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: BryanC on September 05, 2018, 06:15:24 AM

Title: Why is CO2 a by-product of NAD+ reactions in the Kreb's cycle?
Post by: BryanC on September 05, 2018, 06:15:24 AM

NAD⁺ is reduced to NADH in the reactions below:

Pyruvate oxidation
NAD⁺ + pyruvate + CoA -> NADH + H⁺ + CO₂ + Acetyl-CoA

3rd step of Kreb's cycle
NAD⁺ + Isocitrate -> NADH + H⁺ + CO₂ + α-ketoglutarate

4th step of Kreb's cycle
NAD⁺ + α-ketoglutarate + CoA -> NADH + H⁺ + CO₂ + Succinyl-CoA

Is there a reason why CO2 is produced when there is a reduction of NAD⁺?

The texts I have so far simply state that CO2 is derived from the carbon atom that is lost in the hydrocarbon molecule. However, that doesn't seem to explain the core reason why this happens.

Title: Re: Why is CO2 a by-product of NAD+ reactions in the Kreb's cycle?
Post by: Arkcon on September 05, 2018, 08:25:15 AM

If you get a reduction, how is that accomplished?  What causes a reduction?  https://en.wikipedia.org/wiki/Citric_acid_cycle#Steps

Title: Re: Why is CO2 a by-product of NAD+ reactions in the Kreb's cycle?
Post by: Babcock_Hall on September 05, 2018, 10:49:10 AM

I think it helps to assign oxidation numbers to carbon atoms and to tally up electrons.

Title: Re: Why is CO2 a by-product of NAD+ reactions in the Kreb's cycle?
Post by: Babcock_Hall on September 11, 2018, 09:03:54 AM

ON (C) = (number of bonds to O, N, etc) - (number of bonds to H).