What type of receptor binds adrenaline/epinephrine to stimulate glycogen breakdown?

The ß-adrenergic receptor binds to adrenaline (or epinephrine), which plays a key role in the fight-or-flight response by stimulating glycogen breakdown. These receptors are part of the G protein-coupled receptor (GPCR) family, which activate intracellular signaling cascades upon binding their ligands.

When epinephrine binds to the ß-adrenergic receptor, it triggers a conformational change in the receptor that activates an associated G protein. This, in turn, leads to the activation of adenylate cyclase, an enzyme that converts ATP to cyclic AMP (cAMP). The rise in cAMP levels activates protein kinase A (PKA), which phosphorylates specific target enzymes, including glycogen phosphorylase. This phosphorylation activates the enzyme that catalyzes the breakdown of glycogen into glucose-1-phosphate, thereby increasing glucose availability in the blood.

This mechanism is crucial because it highlights the role of signal transduction in cellular responses to hormones like epinephrine, demonstrating how an extracellular signal can elicit a robust metabolic response. Understanding the specific receptor type and pathway involved is essential for appreciating the physiological effects of adrenaline in energy mobilization.