Adenosine triphosphate is the universal energy molecule in cells. Three phosphate groups; breaking the terminal phosphate releases the energy to drive nearly every cellular process.
Mechanism — Synthesized via three systems: ATP-PCr (instant, short duration — first 10 sec of effort), glycolysis (anaerobic, 30 sec to 2 min), and oxidative phosphorylation (aerobic, minutes to hours). Mitochondria are the dominant producer. Body turns over its body weight in ATP daily.
Use case — ATP production is the integrated readout of metabolic health. Support via mitochondrial density (Zone 2 + heavy lifting), NAD+ pool, CoQ10, magnesium, and substrate availability (carbohydrate for glycolytic effort, fat for aerobic).
Caveats — Direct ATP supplements have negligible bioavailability. Build ATP production capacity, don't try to swallow the molecule.