# In cellular respiration, what is being oxidized and what is being reduced?

Aug 28, 2016

${\text{NAD}}^{+}$ and $\text{FADH}$ are being reduced and later oxidezed. The molecule they receive the electrons from are being oxidized.

#### Explanation:

$\textcolor{red}{\text{The basic terms}}$
Oxidation and reduction is about the transfer of electrons:

• oxidation = a molecule loses electrons
• reduction = a molecule gains electrons

$\textcolor{red}{\text{Electron carriers in cellular respiration}}$
An important part of cellular respiration is the transfer of electrons. In the first two phases of cellular respiration (glycolysis and Krebs cycle) electrons are transferred to a carrier molecule. In the third phase (electron transport chain) the electrons are taken from the carrier and used to make energy (ATP).

The carriers are:

${\text{NAD"^+ + "2H" + 2 e^- " " harr " " "NADH" + "H}}^{+}$
${\text{FAD" " "+ "2H" + 2 e^- " " harr " " "FADH}}_{2}$

$\textcolor{R e d}{\text{What gets reduced and what gets oxidized?}}$
The molecules ${\text{NAD}}^{+}$ and $\text{FADH}$ gain electrons, so these are being reduced .

Electrons are coming from molecules in glycolysis and the Krebs cycle, these are being oxidized :

• glyceraldehyde-3-phosphate
• pyruvate
• isocitrate
• $\alpha$-ketoglutatrate
• succinate
• malate

In the last phase of cellular respiration, the electron transport chain, ${\text{FADH}}_{2}$ and $\text{NADH}$ are also being oxidized when they give off their gained electrons.