How does epinephrine break down glycogen?

Epinephrine breaks down glycogen through a signaling cascade that begins when it binds to adrenergic receptors on liver and muscle cells. This binding activates adenylate cyclase, leading to an increase in cyclic AMP (cAMP) levels, which then activates protein kinase A (PKA). PKA phosphorylates glycogen phosphorylase, the enzyme responsible for glycogenolysis, promoting the breakdown of glycogen into glucose-1-phosphate. This process ultimately increases glucose availability for energy during stress or "fight-or-flight" responses.