# Question #50238

Jul 20, 2016

It is a reduction reaction that plays an important role in cellular respiration.

#### Explanation:

Gaining electrons
The conversion of $\text{FAD}$ to ${\text{FADH}}_{2}$ is an example of a reduction reaction. In this case falavin adenine dinucleotide ($\text{FAD}$) gains 2 electrons and 2 hydrogen atoms. The reaction is:

$F A D + 2 {e}^{-} + 2 {H}^{+} \leftrightarrow F A D {H}_{2}$

$F A D$ can be seen as a carrier for electrons. This reduction reaction happens in the citric acid cycle when fumurate is formed from succinate (see image).

As you can see, a similar thing happens to ${\text{NAD}}^{+}$ which takes up two electrons and one hydrogen atom. This nicotinamide adenine dincleotide (${\text{NAD}}^{+}$) is also a carrier of electrons.

Losing electrons
Of course this carrying of electrons has a purpose. The electrons are used in the electron transport chain of cellular respiration. The final goal of the process is to generate ATP, which is the main energy source for all cellular processes.

This transport chain that finally produces ATP requires electrons, The electrons are provided by the $\text{NADH}$ and ${\text{FADH}}_{2}$. When these molecules lose the electrons they 'carry', it is called an oxidation reaction (as opposed to a reduction reaction).