a.There are three signaling pathway
1- Reception in which molecule binds to receptor
2- Signal transduction in which activation of intracellular pathway and enzyme occur.
3- Cellular response in which specific response of cell occur according to receptor and ligand.
b. Three types of receptors are
autocrine receptors are signaling pathway in which cell releases its molecule and bind to its own cell receptor example cancer cells while paracrine in which ligand binds to other nearby cell receptor and it is used during development and in endocrine cell target distinct cell and travel through blood stream like hormones functioning.