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.
Optimal alertness: Healthy sleep allows us to function optimally when we are awake, to have what is called optimal alertness. We have all experienced varying degrees of being awake, from groggy to alert to hyper-alert.