The Mitochondrial Free Radical Theory of Aging - Supernova: Pliki

An Introduction to Mitochondria
Fig. 2.4. Acetaldehyde, CoA and acetyl CoA.
I say it was worked out in the 1930s, but in fact one very important step was absent until
1953. Until then, it was thought that the TCA cycle created no ATP. But in fact, one of the steps
in Krebs's original formulation—the conversion of α-oxoglutarate to succinate—occurs in
two steps, with coenzyme A as a cofactor, and the latter of these steps includes the creation
of one molecule of guanine triphosphate (GTP) from GDP and phosphate. 18 This reaction
is followed by a transphosphorylation reaction, mediated by the enzyme nucleoside
diphosphate kinase, in which the GTP is turned back into GDP and the released phosphate
is transferred to ADP making ATP. Many bacteria skip this last complication and
phosphorylate ADP directly in the succinate synthesis step. 19
2.3.3.3. Repaying the Oxygen Debt: Respiration
At this point, the destruction of one molecule of glucose has consumed six molecules
of water and yielded six molecules of carbon dioxide. Additionally, it has stored up 24
hydrogen atoms—12 from the original glucose and 12 from the water—whose protons are
free in the aqueous medium, while their electrons are carried by ten molecules of NADH
and two of FADH2. There is a limit to our supply of NAD + and FAD, and also to the number
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