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

#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.