And when our blood concentration of glucose basically decreases what that means is our liver cells will begin to break down glycogen to glucose and release that glucose into the blood and that will help maintain a correct concentration of glucose in our blood. At the same time, for instance, if we're exercising our skeletal muscles will begin to break down glycogen to glucose and use that glucose to form the energy ATP molecules needed to carry out the proper voluntary motions that are required for that particular exercise. So basically during these circumstances our body wants to break down glycogen to glucose but at the same time it wants to stop the process of the synthesis of glycogen glycogenesis. So this is a signal transduction pathway that essentially allows us to carry out these two processes to turn on glycogen breakout and turn off glycogen synthesis. So let's imagine where in our liver cell so we have glucagon and to a very small extent epinephrine are the primary messengers that bind to these receptor molecules on liver cells. And once the glucagon binds onto the glucogon receptor it basically stimulates the GDP to leave and a GTP to enter this green g protein.