1.Both rhodopsin in vision and muscarinic acetylcholine receptor system

in cardiac muscle are coupled to ion channels via G proteins. Describe the similarities and differences between these two systems.


2 Why do you suppose that phosphorylation/dephosphorylation, as opposed to allosteric binding of small molecules, for example, has evolved to play such a prominent role in switching proteins off and on in signaling pathways?


3 Summarize the steps in the cycling of GTPase switch proteins from active to inactive states.


4 Review the steps for ligand-induced activation of effector protein mediated by trimeric G proteins. Suppose you have isolated a mutant Gα that has increased GTPase activity, what effect would this mutation have on the G protein and the effector protein?


5 How does the body respond to decreases in blood glucose levels below about 5 mM?