In any signalling pathway, the ultimate signal being transduced is the need for something to happen, embodied in the ligand which binds to a receptor. This information takes many forms but always has the same basic meaning. The first passage, from outside to inside, comes through the change in the shape of the receptor protein.
Work Step by Step
This question points to the basic idea that no matter the step of signal transduction and the form that the signal takes at a given point, the same basic point of information is being carried.