Adrenaline is an amine hormone released during the 'fight-or-flight' response that stimulates hepatocytes to break down glycogen into glucose.
Which of the following correctly describes the mechanism of action of adrenaline on a hepatocyte?
Adrenaline, being lipid-soluble, diffuses through the cell-surface membrane to bind to a cytoplasmic receptor, which then translocation to the nucleus to act as a transcription factor.
When adrenaline binds to its transmembrane receptor, it stimulates the activation of adenylyl cyclase, which catalyses the conversion of ATP to cyclic AMP.
Cyclic AMP functions as a protein kinase enzyme, directly phosphorylating and activating glycogen phosphorylase in the cytoplasm.
Adrenaline acts as the second messenger, activating G-proteins inside the hepatocyte that directly hydrolyse ATP to ADP to release free energy.
