ATP in Plant Mitochondria: Substrates, Inhibitors, and Uncouplers

Adenosine triphosphate (ATP) is the energy carrier of the cell and in eukaryotic cells is synthesized via photosynthesis and respiration. Within respiration, there is a low level of ATP synthesis associated with glycolysis in the cytoplasm; however, the majority of ATP is synthesized via oxidative phosphorylation which occurs within mitochondria, specifically via the operation of an electron transport chain (ETC) in the inner mitochondrial membrane. In mammals, flux through the respiratory pathway is tightly regulated by the ATP/adenosine diphosphate ratio or adenylate energy charge of the cell. Plants, unlike mammals, must synthesize all of their cellular components. In plants, the presence of a nonphosphorylating pathway in the mitochondrial ETC and an uncoupler protein in the inner membrane overcomes this restriction by adenylate control. In plants, respiration not only is important for energy production but also has a major role in biosynthesis and anabolic reactions, in programmed cell death, and, more recently, has been implicated as stress response signaling sensor.