The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Adenynyt Cyclase Beta-2 Adrenergic Epinephrine Receptor Cyclic AMP Plasma Membrane VB Protein kinase A -ATP ADP Phosphorylase Kinase GDP G Protein -ATP VA ATP GTP GDP GTP ADP Glycogen Phosphorylase Glycogen! Glucose-1-Phosphate Glycolysis Figure 1. A simplified model of the epinephrine signaling pathway in muscle cells A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim? Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate. Epinephrine is a signaling molecule that binds to a transmembrane protein The G protein in the epinephrine signaling pathway consists of three different subunits. Phosphorylase kinase catalyzes the hydrolysis of ATP.