molecule is combined with a four-carbon molecule of oxaloacetic acid to form a six-carbon molecule called citric acid. Each citric acid is oxidized to form carbon dioxide plus a five-carbon compound which, in turn, is oxidized to form carbon dioxide plus a four-carbon compound. This four-carbon compound is then converted into oxaloacetic acid, at which point the whole cycle can begin again. Since each acetyl-CoA contains two carbons, it takes two cycles to release the remaining four carbons of the glucose as carbon dioxide. During these two cycles, two additional ATP and six additional NADre are produced as are two FADre, an energy-rich electron acceptor compound very similar to NAD. At this point, a total of four ATP, ten NADre, and two FADre have been produced; the latter twelve molecules contain much of the energy that was present in the original glucose molecule.
