Mitochondrion is the main site for oxidative phosphorylation and ATP production in the cell, providing chemical energy required for cellular activities, and is considered to be the cell’s “power generator.” Aside from providing energy, the mitochondrion also participates in processes such as cell differentiation, signal transduction and apoptosis, and is also able to modulate cell growths and cell cycles.
Hayflick limit: The Hayflick limit refers to the number of times telomeres can divide before cell division stops. The theory was proposed by Leonard Hayflick in 1965, who proved that normal cultured human cells can divide up to 52 times before entering the aging phase, and refuted Alexis Carrel’s prior contention that cells are immortal. The telomere DNA will shorten after each cell division, decreasing the cell’s longevity.