Question

how is cyanide able to bring death so quickly

Answer 1

Cyanide will bind to cytochrome-c in the electron transport chain and prevent it from either accepting or donating electrons. The effect of this is that ATP generation from the electron transport chain stops. The body is quickly depleted of ATP and without ATP, every function in your body that requires ATP will also stop.

Answer 2

also cyanide binds irreversibly with the
heme portion of hemoglobin, result-- no o2 transport

Answer 3

http://en.wikipedia.org/wiki/Cyanide_poisoning read about it.