Question

In terms of the functioning of the beta-adrenergic pathway, give the rationale for the fact that the alpha subunit of the G-protein is secluded in a trimeric protein and bound to a GPCR when no epinephrine is available.

Answer 1

# When epinephrine bound to the GPCR, it causes a conformational change in the receptor. This coformational change will allow the GPCR to act as a guanine nucleotide exchage factor. Exchange of the GDP with GTP will actiavte the G protein and cuases the dissociation of G from the β and γ subunits. This causes further intracellular signalling.

Therefore, from the above explanation it is clear that the epinephrine ligand is more important to activate the GPCR. without the signal, there will be no conformational changes to activate the G protein.