Figure 1.

Model for high-energy phosphoryl transfer via adenylate kinase. As energy is transported from the mitochondria to the sites of utilization such as proton pumps or motors, the intracellular system supports an energy network of creatine kinase (CK), adenylate kinase (AK), and the localization or transport of the mitochondria themselves, in addition to simple diffusion. The presence of extracellular secretory AKs outside the cells suggests the existence of extracellular energy metabolism. In addition, intercellular energy networks, such as extracellular vesicles (EVs) are thought to exist.