A red blood cell has no nucleus and is therefore unable to make the proteins necessary to maintain itself.

Because of this, red blood cells have a relatively short life span of about 120 days. Given that we have about 25 trillion red blood cells, show that more than 208 billion red blood cells die and are replaced each day. Also show that, in the 20 seconds it took you to read this problem, about 48 million red blood cells died and were replaced.