4. ATP--The Common Currency of Energy Plants and animals use cellular respiration to turn the sugar created by photosynthesis into potential energy, mainly in the form of adenosine triphosphate (ATP). ATP is often called the "common currency" of energy because it's used by almost every living thing: bacteria, plants--even complex organisms like Tom Cruise. However, individual molecules of ATP are not exchanged between organisms, so how does it operate like currency? As you can see below, ATP has three phosphate groups attached to adenosine. When the outermost phosphate group is detached and becomes adenosine diphosphate (ADP) and inorganic phosphate (Pi), 7.3 kcal (31 kJ) per mole of energy is released. If ATP is hydrolyzed in a test tube, the surrounding water is warmed by this energy, but in an actual cell that energy is used when an enzyme catalyzes a chemical reaction, a muscle moves, or a neural signal is transmitted. Adenosine Adenine 3 phosphate groups