[0:00] Cancer, heart disease, allergic reactions, 
drowning in molasses, getting your head bitten  
[0:06] off by a grizzly bear – there are LOTS 
of things out there that can kill you.
[0:10] But when it comes to the inner 
workings of the human body,  
[0:14] it turns out that everybody 
actually dies from the same thing.
[0:17] Hi, I’m Kate and this is MinuteEarth.
[0:20] We often use specific biological hallmarks,  
[0:23] like a person’s heartbeat or brain 
activity, to divide life from death.
[0:28] But there’s something much more fundamental 
that drives these processes, and all the  
[0:32] other life-sustaining processes 
constantly going on in your body:
[0:35] ATP, our body’s energy source.
[0:38] Every single cause of death out there 
actually kills us by interfering with  
[0:42] our ability to produce ATP, powering down 
the very processes that keep us alive.
[0:48] OK, every cause of death except 
something like a nuclear explosion,  
[0:52] which obliterates the need for 
these processes in the first place.
[0:56] But for the vast majority of 
us, death is a dearth of ATP.
[1:01] It takes two ingredients to make ATP:
[1:03] fuel and oxygen… without enough of either one,  
[1:07] your cells can’t produce 
enough ATP to keep you alive.
[1:10] Starvation, for instance, is a matter of 
not having enough fuel to convert into ATP.
[1:15] But cells are really good at scavenging 
our bodies’ stores of fat, protein,  
[1:19] and carbs, so in most causes of death, 
fuel isn’t the limiting factor… oxygen is.
[1:25] Normally, our respiratory system 
grabs oxygen from the air, then our  
[1:29] circulatory system shuttles it to various 
organs, where cells use it to make ATP.
[1:34] Most causes of death interrupt 
this journey in some way.
[1:37] Some mess with the initial oxygen-acquiring 
part; like, pneumonia fills the lungs with fluid,  
[1:43] preventing oxygen from making it into 
the bloodstream in the first place.
[1:47] Other respiratory problems, like lung 
cancer, anaphylaxis, and drowning,  
[1:51] also prevent the respiratory system from 
effectively grabbing oxygen from the air.
[1:56] Most causes of death, though, interfere 
with the second part of the oxygen pathway.
[2:00] Like heart disease, the most common cause 
of death worldwide, narrows the arteries,  
[2:05] restricting the flow of blood 
throughout the rest of the body.
[2:08] Electrocution messes with the electrical 
signals that regulate the pumping of the  
[2:12] various chambers of the heart, leaving 
them unable to effectively pump blood.
[2:16] Strokes – another major cause of death – 
happen when blood can’t reach the brain.  
[2:20] And sudden trauma can cause so much 
blood loss that the pressure in the  
[2:24] circulatory system drops, leaving it 
unable to move blood through the body.
[2:29] In each of these cases, even though 
enough oxygen has made it into the body,  
[2:33] that oxygen isn’t getting carried to 
cells, where it’s needed to produce ATP.
[2:38] And in a few especially-weird causes 
of death, plenty of oxygen is making  
[2:42] it into the body AND getting where it 
needs to go, but cells can’t use it.
[2:47] Cyanide, for instance, messes with 
the cellular machinery that makes ATP,  
[2:52] leaving it unable to use oxygen 
to complete the reaction.
[2:55] There are a ton of ways to interfere with the ATP  
[2:58] production pathway – that’s why there 
are so many so-called “causes of death”.
[3:03] But no matter where – or how – the pathway 
fails, the ultimate result is the same:
[3:08] your body can’t produce enough energy to carry out 
the processes needed to actually maintain life.
[3:14] In the end, a lack of ATP is the ultimate 
cause of every single case of RIP.