For a G protein to play its part in moving events forward in a signal pathway:_____.
a. cGMP must occupy the otherwise empty nucleotide-binding site.
b. GDP must be released, and a GTP must occupy the nucleotide-binding site.
c. it must be linked to a specific intracellular receptor.
d. cGMP must leave the otherwise occupied nucleotide-binding site. GTP must be released, and a GDP must occupy the nucleotide-binding site.