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Any chemical that uncouples the process of respiration from that of phosphorylation. For example, in glycolysis the formation of 3-phosphoglycerate from 3-phosphoglyceroyl phosphate normally yields two molecules of ATP. However arsenate prevents the formation of ATP at this point. Arsenate also acts as an uncoupling agent in oxidative phosphorylation. Many other uncouplers of oxidative phosphorylation are known, most of which contain an aromatic ring and an acidic group. Examples are 2,4-dinitrophenol (DNP) and dicumarol. DNP has been used to investigate many aspects of plant physiology. For example, in research on phloem transport it has been shown that DNP inhibits translocation of assimilates. This implies there is some energy-requiring metabolic component in phloem transport and that the process is not purely due to osmotic potential and turgor pressure. DNP has also been used to investigate the theory that the respiratory climacteric that occurs during fruit ripening is due to the accumulation of natural uncoupling agents (uncoupling agents promote respiration as they cause a build-up of ADP).
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