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

1 Answer
Aug 28, 2016

#"NAD"^+# and #"FADH"# are being reduced and later oxidezed. The molecule they receive the electrons from are being oxidized.

Explanation:

#color(red)"The basic terms"#
Oxidation and reduction is about the transfer of electrons:

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

#color(red)"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:

  • Nicotinamide adenine dinucleotide
    #"NAD"^+ + "2H" + 2 e^- " " harr " " "NADH" + "H"^+#
  • Flavin adenine dinucleotide
    #"FAD" " "+ "2H" + 2 e^- " " harr " " "FADH"_2 #

#color(Red)"What gets reduced and what gets oxidized?"#
The molecules #"NAD"^+# and #"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, #"FADH"_2# and #"NADH"# are also being oxidized when they give off their gained electrons.