Let me preface this by saying I am a senior in high school taking AP Biology. Currently, we are studying glycolysis, TCA cycle, and oxidative phosphorylation.
Were taught many years ago that the oxidation of glucose to harvest energy can be generalized by
C6H12O6 + 6O2 -> 6CO2 + 6H2O
I am trying to account for where all of these molecules are either consumed or made.
One glucose is used in glycolysis, which makes 2 NADH + 2 protons. Pyruvate oxidation creates an additional 2 NADH + 2 protons and 2 CO2 (per glucose). Two cycles of the TCA cycle produce 6 NADH + 6 protons, 2 FADH2, and 4 CO2. So far, the glucose and the CO2 have been entirely accounted for. I excluded water because two waters are made from glycolysis but 2 are used again in TCA cycle.
So, 10 NADH + 10 protons and 2 FADH2 enter the electron transport chain. They donate, collectively, 12 pairs of electrons, which ultimately result in the reduction of 3 molecules of oxygen (O2) to make 6 H2O. O2 doesn't fit. I say 3 molecules and not 6 because each oxygen molecule needs 4 electrons (and protons) before it can become 2 H2O.
This does not match with the generalized equation. I have consulted a few biochemistry texts, but was unsuccessful in finding a satisfactory explanation. Can someone please explain this?
