If all the cell in our body are replaced at some point in our life, why do we get old and die?

Question

If all the cell in our body are replaced at some point in our life, why do we get old and die?

In: Biology

Answer 1

There are only so many times a living cell can divide. That’s dictated by a protein inside our cells called Telomeres which gets shorten every time cells divide. Once that Telomeres reaches terminal length (after 50-70 cell divisions), those cells simply stops dividing and dies.