Epinephrine binds a membrane receptor, activates a G protein and stimulates cAMP production to create rapid intracellular responses, linking signal detection to a specific target-cell response.
Coverage 2025–2025 · Updated 15 Jul 2026
Adrenaline binds a GPCR and activates a cAMP pathway that rapidly promotes glycogen breakdown in target cells.
The receptor activates a stimulatory G protein, adenylyl cyclase makes cAMP, and a kinase cascade activates glycogen phosphorylase. Phosphodiesterase and receptor reset limit the response.
Follow the sequence:
One adrenaline molecule can trigger many cAMP molecules and therefore amplify glycogen breakdown during exercise.
Adrenaline does not directly split glycogen at the receptor; the kinase cascade mediates the response.
This objective is assessed through structured response, multiple choice, commonly using Explain.
Explain
Build the answer around this relationship: Epinephrine binds to receptors in the cell membrane.
Representative question
Explain how epinephrine exerts its effects in the cell.
A ligand only affects target cells with the matching receptor. Quorum sensing uses autoinducers and thresholds for group behaviour. Animal signals differ by source, distance, speed, target-cell response, and chemical class. Hydrophilic ligands use transmembrane receptors and relays; steroid and thyroid hormones use intracellular receptors that affect transcription. Named pathways then show the logic: acetylcholine opens sodium channels, GPCRs switch G proteins through GDP-GTP exchange, epinephrine uses cAMP and kinase cascades, insulin RTKs use dimerisation/autophosphorylation to move GLUT4 and promote glycogenesis, steroid hormones change gene expression, and feedback either amplifies or restores stability.
