Mitochondria are membrane-bound cell organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell’s biochemical reactions. Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP). 1
Mitochondria are found in all body cells, with the exception of a few. There are usually multiple mitochondria found in one cell, depending upon the function of that type of cell. 2
The mature egg cell, or oocyte, contains the highest number of mitochondria among human cells, ranging from 100,000 to 600,000 mitochondria per cell. 3