Structure of Haemoglobin: Haemoglobin is an aggregation of four globular proteins (typically two alpha and two beta subunits), each with an embedded haeme group. Each haeme group allows the binding of an oxygen molecule.
Here's another intriguing case from the Guinness World Records. In 1964, a 17-year-old high school student named Randy Gardner beat the world record for sleep deprivation by staying awake for 264 hours (11 days) without using any stimulants.
Because even I who has chronic insomnia can stay awake for 5 days but I am not without any sleep because even what I think was a blink lasted for 15 seconds. Sleep is needed and the body would do everything to get it, even if it knows something bad will happen if you go to sleep (such as in the streets)