The clever aspect of this part of the process is that the plants don’t release the free energy stored as isolated hydrogen in one go. Instead, they divide up the free energy held in the isolated hydrogen into other chemicals that have specifically evolved to store Gibbs free energy. The most common of these is adenosine triphosphate or ATP. Think of ATP as a tiny molecular spring that becomes coiled when it receives free energy. That packet of energy can then be accessed on demand by the chemical equivalent of releasing the spring in the ATP.
