Mitochondria are located in the cytoplasm outside the nucleus of the cell and they consist of two sets of membranes, a smooth continuous outer coat and an inner membrane arranged in tubules or in folds that form plate-like double membranes (cristae).

The mitochondria are the principal energy sources of the cell as a result of the presence of specialized enzymes for terminal electron transport, the citric acid cycle, fatty acid oxidation, and oxidative phosphorylation.