Answer
In the 1960s, Martin Rodbell discovered that guanosine triphosphate (GTP) played a crucial role in cell signaling. He identified the involvement of GTP in the activation and deactivation of certain proteins, known as G proteins, involved in transmitting signals within cells. This discovery provided a foundational understanding of how cells communicate and respond to external stimuli, paving the way for further advancements in the field of cell signaling and physiology.