Mitochondria are granular or filamentary self-replicating organelles present in the cytoplasm of almost all eukaryotic cells.
Mitochondria are surrounded by a double membrane consisting of a mitochondrial matrix, an inner membrane, an intermembrane space, and an outer membrane. Inner membranes of mitochondria form numerous protrusions (cristae) inside the mitochondria. Although theymitochondria have circular DNA and protein synthesis apparatus, most of the proteins are encoded by cellular DNA and come from the cytosol.
Mitochondria are the center of cellular respiration, metabolism, and energy production. In particular, mitochondria perform the transformation of pyruvate and fatty acids into acetyl CoA. These organelles are directly involved in the oxidation of acetyl-CoA in the Krebs cycle, leading to the formation of NADH and two CO2 molecules. Next, the mitochondrial inner membrane contains proteins that are the components of the respiratory chain providing the transfer of electron and protons from NADH to oxygen resulting in the formation of H2O. Finally, electron transport chain localized in the mitochondrial inner membrane provides the formation of ATP associated with the activity of the ATP-synthetase complex.