A little something from my note-taking today in biochem...right now it makes perfect sense, but I'm pretty sure that if I look at it again tomorrow I'll have NO idea what in the world it's talking about...
Method of action of glucagon
v Receptor on cell surface involving cAMP.
v Activates a cAMP dependent protein kinase. This causes the phosphorylation of phosphorylase kinase, which activates phosphorylase, phosphorylating the above-mentioned enzymes regulating the synthesis/breakdown of glycogen. Using this kinase increases the signal by several orders because each of the different enzymes activates a number of others further down the chain. 1 molecule of glucagon can activate 1000 phosphatase enzymes.