I have learned that human cells have an expiry date. When cells divide, they replicate their chromosomes, which leads to the loss of their DNA at the ends. The telomeres that help to protect cells shrink after every cell division, and when they get depleted, they leave behind senescent cells. These senescent cells increase as people age, and they do not die. They are the ones that make people prone to diseases since they destroy the tissues that surround them (Youtube.com, 2017). I also learned that aging is caused by the underproduction or slow supply of the NAD+ cells. NAD+ cells are the ones that alert other cells to look after themselves. According to Barzilai (2016), NAD+ cells are essential for one to live, and without them, a person can die within 30 seconds. Therefore, when people do not receive enough NAD+ cells, they become susceptible to a wide range of diseases.

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