text: Endergonic reactions can be pushed by coupling them to another reaction which is strongly exergonic, through a shared intermediate.
  This is often how biological reactions proceed.  For example, on its own the reaction
  may be too endergonic to occur.   However it may be possible to make it occur by coupling it to a strongly exergonic reaction – such as, very often, the decomposition of ATP into ADP and inorganic phosphate ions,  ATP → ADP + P, so that
  This kind of reaction, with the ATP decomposition supplying the free energy needed to make an endergonic reaction occur, is so common in cell biochemistry that ATP is often called the "universal energy currency" of all living organisms.