To be effective, intracellular signaling molecules must be inactivated/removed when their effects are no longer needed. Provide the methods by which this occurs for the following classes of intracellular messengers: i) G proteins, ii) 7-helix receptors, iii) cAMP iv) cGMP v) Ca2+ vi) IP3 vii) DAG viii) Phosphatidic acid ix) Ceramide x) Nitric oxide xi) Cyclic ADP-ribose