Mitochondria provide the energy a cell needs to move, divide, and produce secretory products. They are the power centers of the cell. They are about the size of bacteria but may have different shapes depending on the cell type. Mitochondria have been implicated in several human diseases, including mitochondrial disorders and cardiac dysfunction, and may play a role in the aging process.
The number of mitochondria in a cell varies widely by organism and tissue type. Many cells have only a single mitochondrion, whereas others can contain several thousand mitochondria.
The mitochondrion is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, the intermembrane space, the inner membrane, and the cristae and matrix. Mitochondrial proteins vary depending on the tissues and species. In human, 615 distinct types of proteins were identified from cardiac mitochondria.