ATP (adenosine triphosphate) is common to all organisms from bacteria to mammals. It is the key substance, the general currency in energy conversions within living organisms: when its terminal high-energy phosphate bond is hydrolyzed, free energy becomes available for biological activities such as muscle contraction, nerve excitation, and active transport, and also for the synthesis of a number of compounds, including proteins and nucleic acids in cells. To be useful, however, ATP hydrolysis must be very closely coupled with another system; in the absence of such coupling, the free energy can go to waste as heat. ATP is synthesized from ADP (adenosine diphosphate) and Pi (inorganic phosphate) during both glycolysis in the cytosols and, more effectively, oxidative phosphorylation in mitochondria. Thus, the energy of light that is converted to carbon-carbon bonds in carbohydrates, during photosynthesis in green plant chloroplasts, is recovered and stored in the high-energy bond of ATP.
The history of the discovery of ATP has been well documented by Dorothy Needham, Marcel Florkin, and, more recently, by Fritz Schlenk. l However, there still remain questions regarding the circumstances leading to the initial discovery, in the two widely separated laboratories that reported the identification of this key substance, in the later months of 1929. The present paper is concerned with this early history of ATP, and also with the later establishment of the true structure of the molecule, after some incorrect proposals had been put forward.