4. There are a variety of receptors and second messenger systems in cells that in many cases exhibit cross-talk with each other (the activation of one can influence the behavior of another). Given this fact understanding how ligand activated receptors works is not as easy as presented in your book or in class. a. There are a number of different ligands that interact with their respective receptors. How do receptors for testosterone, ferro transferrin and Fibroblast Growth Factor differ from each other with respect to the location and function of their receptors