1
$\begingroup$

I've heard that $\ce{NAD^+}$ gains a Hydrogen proton during glycolysis and the Krebs cycle and becomes reduced to $\ce{NADH}$. However, isn't reduction when a molecule receives an electron?

Maybe I've been misinformed? Does $\ce{NADH}$ gain a Hydrogen electron, not a proton?

Improve this question
$\endgroup$
13
$\begingroup$

You are correct that reduction is simply a gain of electrons. This results in a decrease in oxidation number.

You know that NAD+ is reduced by this process because it starts off with a positive charge (+1) and ends up with a neutral charge (0).

The reducing agent that is donating the electrons is the hydrogen. More correctly, the electrons come from the hydride (H-).

The hydride is represented by 2 electrons on this redox diagram: enter image description here

As you can see, the reduction reaction transfers a proton (H+) and hydride electrons (H- or 2e-) to NAD+. One electron goes to the nitrogen, and the other to the carbon where the proton binds. More details on the redox reaction of NAD can be found here.

Improve this answer
$\endgroup$
  • 2
    $\begingroup$ Hydride anions do not exist in biochemical reactions. $\endgroup$ – Chris♦ Dec 5 '17 at 19:53

Not the answer you're looking for? Browse other questions tagged or ask your own question.