ATP during and after death

If I remember correctly, anaerobic metabolism can produce ATP in a given cell for around 30 seconds before your cells must switch over to aerobic metabolism. This is why you can't sprint etc. for very long. There may be some differences between cells that are specialized for anaerobic and those that aren't, because the former can store a bit more glucose and creatine phosphate (allows some short-term regeneration of ATP), but you run through your cells' reserves very quickly. We're talking no more than few minutes, though. There's a reason we die within minutes when we can't breathe. And some tissue, such as nervous tissue, is even more dependent on aerobic metabolism. Extremely low temperatures can slow this process, but of course freezing someone would cause cell membranes to burst.

Normally, cellular membranes start to rupture within 4-10 minutes of death too, depending on ambient temperature, because CO2 and lactic acid build up, lowering pH in the fluid between cells. Once a cell membrane is ruptured, that cell cannot function, and ruptured organelles within the cell release digestive enzymes which start to "eat" the cells from within.

And once the heart stops beating, of course, there is no new glucose (blood sugar) that can be taken up by a cell either, so if anything, anaerobic capacity ceases even more quickly after death. Our cells run out of ATP very quickly after death, and they exhaust their capacity to renew it anaerobically very quickly as well. Now people can survive cold water drownings just above freezing for longer periods of time, because cold temperatures lower metabolism and demand for ATP as well as the process of cellular decomposition. But an extremely cold corpse would be unable to function metabolically because, well, it's cold.

Now there are organisms that can live of different types of anaerobic fermentation, as it's called. They are generally small and simple, or have much lower metabolic rates than we do.