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#Question id: 14685


In dark-adapted rod cells, a high level of cGMP keeps cGMP-gated nonselective cation channels open, leading to hyperpolarization of the plasma membrane and neurotransmitter release. 
B - Light absorption generates activated rhodopsin, R*, which binds inactive, GDP-bound Gαt protein and mediates the exchange of GDP for GTP . 
C- The free Gαt∙GTP activates PDE by binding to its inhibitory γ subunits and dissociating them from the catalytic α and β subunits . Relieved of their inhibition, the α and β subunits of PDE hydrolyze GMP to cGMP . 
D- The resulting decrease in cytosolic cGMP leads to dissociation of cGMP from the cation channels in the plasma membrane and the closing of those channels . 
E- The membrane then becomes transiently hyperpolarized, and neurotransmitter release is reduced. 

#Unit 4. Cell Communication and Cell Signaling
  1. B , D and E       
  2. A, B, and E
  3. B, C, and D       
  4. C, D, and E