noun, singular: mitochondrion
Spherical or rod-shaped organelles found within the cytoplasm of eukaryotic cells, and are referred to as the “powerhouse of the cell since they act as the site for the production of high-energy compounds (e.g. ATP), which are vital energy source for several cellular processes.
They produce large amounts of energy through oxidative phosphorylation of organic molecules during cellular respiration. That is, they are capable of using glucose and oxygen to produce energy (and releasing carbon dioxide and water in the process) for use in many metabolic processes. Thus, it is not surprising to find several mitochondria in high energy-requiring cells, such as muscle cells.
They are semi-autonomous, self-reproducing organelles because they contain their own genome. In fact, their DNA has become an important tool in tracking genetic histories since their genetic material is present in only one copy, and does not recombine in reproduction.
According to the endosymbiotic theory, mitochondria might have been the remnants of early bacteria engulfed by ancient eukaryotic cells a billion years ago that might have evolved and become energy-yielding structures within eukaryotic cells at present.