Describe the key events that occur during the aerobic metabolism of glucose, remarking on the net energy gained by such reactions.
During the Krebs citric acid cycle, each two-carbon acetic acid 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.
