A Series of Medical Articles: #2. Biological Aging

Individuals go through several stages of life throughout their lives. They start as infants, grow up to be adults, and ultimately die. Although average lifespans vary across species, aging is a universal phenomenon. But why do we age?

Diving into Cell Regeneration
The biological explanation for aging can be found in the mechanisms of cell regeneration. First, biological maturation in an individual occurs as a result of cells dying off since they can no longer renew themselves as quickly as they once could. Mitosis (cell replication) happens at its fastest during childhood and adolescence. The pace at which organisms undergo mitosis slows as they age, yet cells continue to die at a steady rate. As a result, fresh cells would be unable to quickly replace older ones.

Also, the occurrences of cells dying off in older people may be linked to stem cell development. As a person gets older, fewer stem cells are produced, and their abilities diminish. This can be seen in the varying recovery times required for people at various phases of life, as older people are more susceptible to injuries and heal more slowly. Physical aging happens as a result of the longer time it takes for stem cells and regular body cells to regenerate.

Comparison of Young and Old Telomeres

Lastly, throughout the continued cell regeneration, the telomeres of chromosomes shorten, causing biological aging. Telomeres are sections of our chromosomes that stabilize them. They are associated with both ends of our chromosomes. Telomeres, on the other hand, shorten when our DNA replicates. Our bodies have an enzyme called telomerase that adds sets of TTAGGG nucleotides back to the telomeres to address this problem. However, as people get older, telomerase can't keep up with the rate of telomere shortening. Mitosis would be stopped and the cell would die soon if the chromosomes became too short. Apoptosis, or cell death, would accelerate the aging process.