ABSTRACT
Energy is the basis of all cellular activity ranging from heavy lifting to intense thinking. An estimated total of 10 quadrillion (10,000,000,000,000,000) mitochondria act as power sources in human cells. These bacteria-like organelles, strategically located in cells where they are needed, burn fat and other energy-rich foodstuffs to produce the common energy currency of all cells called ATP (adenosine triphosphate). The process of converting food to useful energy by mitochondria is called respiration and consumes most of the oxygen carried by our circulating red blood cells. Mitochondria likely originated from bacteria or archaea but long ago lost their freeliving lifestyle in favor of a permanent endosymbiotic relationship within animal and plant cells. These energy-transducing organelles, which still retain some properties of bacteria, are strictly dependent on their animal hosts for growth but have retained a miniature chromosome of their own called mitochondrial DNA (mtDNA). The mtDNA encodes several genes essential for energy production, and in a strange quirk of nature these genes hold life and death powers over the human organism-acting as a master pacemaker for aging. We begin this story by describing the general nature of energy production by mitochondria and end by de€ning how energy stress can arise and create aging and age-related diseases including Alzheimer’s disease.
