Editing Martin Rodbell (section)

===Research===
Reflecting the increasingly common analogies between [[computer science]] and [[biology]] in the 1960s, Rodbell believed that the fundamental information processing systems of both computers and biological [[organism]]s were similar. He asserted that individual cells were analogous to cybernetic systems made up of three distinct molecular components: discriminators, [[transducer]]s, and [[amplifier]]s (otherwise known as effectors). The discriminator, or cell [[receptor (biochemistry)|receptor]], receives information from outside the cell; a cell [[transduction (physiology)|transducer]] processes this information across the [[cell membrane]]; and the amplifier intensifies these signals to initiate reactions within the cell or to transmit information to other cells.

In December 1969 and early January 1970, Rodbell was working with a laboratory team that studied the effect of the hormone [[glucagon]] on a rat [[liver]] membrane receptor—the cellular discriminator that receives outside signals. Rodbell discovered that ATP ([[adenosine triphosphate]]) could reverse the binding action of glucagon to the cell receptor and thus dissociate the glucagon from the cell altogether. He then noted that traces of GTP ([[guanosine triphosphate]]) could reverse the binding process almost one thousand times faster than ATP. Rodbell deduced that GTP was probably the active biological factor in dissociating glucagon from the cell's receptor, and that GTP had been present as an impurity in his earlier experiments with ATP. This GTP, he found, stimulated the activity in the guanine nucleotide protein (later called the G-protein), which, in turn, produced profound metabolic effects in the cell. This activation of the G-protein, Rodbell postulated, was the "[[second messenger]]" process that [[Earl W. Sutherland]] had theorized. In the language of signal transduction, the G-protein, activated by GTP, was the principal component of the transducer, which was the crucial link between the discriminator and the amplifier. Later, Rodbell postulated, and then provided evidence for, additional G-proteins at the cell receptor that could inhibit and activate transduction, often at the same time. In other words, cellular receptors were sophisticated enough to have several different processes going on simultaneously.