Oxidative Phosphorylation

Mitochondria are believed to be the result of incorporation of a prokaryote with oxidative phosphorylation into another cell, during the Precambrian period. Oxidative phosphorylation was present and integrated into cellular metabolism by the time of the ‘Cambrian explosion’ approximately 540 million years ago. Only organisms with oxidative phosphorylation went on to develop into ‘higher’ animals and plants: i.e. animals and plants having morphologically and metabolically distinct parts with specialized functions that are essential to the life of the organism. In higher animals, oxidative phosphorylation is the primary source of ATP for metabolic and mechanical work, providing most of the energy used in for biosynthesis, maintaining proper ion balance, and mechanical work. In higher plants, it provides energy when photosynthesis is not available, as during periods of darkness, as well as in tissues without photosynthesis (roots etc.). The presence of oxidative phosphorylation in all higher plants and animals implies that it is of great importance to their existence. Oxidative phosphorylation is a fundamental mitochondrial process, linking the tricarboxylic acid (TCA) cycle to the production of adenosine triphosphate (ATP). Subpopulations of tumor cells are strongly dependent on oxidative phosphorylation, for example, glycolysis-deficient cells, PTEN-null cells and SWI/SNF complex mutated cells in lung cancer. In addition, increased oxidative phosphorylation dependency is frequently exhibited by cancer stem cells (CSCs), as well as KRAS ablation-resistant cells in pancreatic cancers.