Complex sentence: Purinergic signaling is a form of extracellular signaling mediated by purine nucleotides and nucleosides such as adenosine and ATP, which activate purinergic receptors in the cell and/or in nearby cells, thereby regulating cellular functions.
Split into simpler sentences: Purinergic signaling is a form of extracellular signaling mediated by purine nucleotides and nucleosides, such as adenosine and ATP. This leads to the activation of purinergic receptors in the cell and/or in nearby cells, thereby regulating cellular functions.