ADH has two actions, one on the kidney and the other on vascular smooth muscle, these actions are mediated by different receptors, different intracellular mechanisms, and different secondary messengers.

a. The major action of ADH is to increase the water permeability of principal cells in the late distal tubule and collecting duct.

b. The receptor for ADH on the principal cells is a V2 receptor, which is coupled to adenylyl cyclase via a Gs protein. 

c. The second messenger is cAMP, via phosphorylation steps, directs the insertion of water channels, aquaporin 2 (AQP2), in luminal membranes.

d. The receptor for ADH on the principal cells is a V1 receptor, which is coupled to phospholipase C via Gq protein.

Which one of the following combination of above statements is correct?

#Question id: 1244

#Unit 4. Cell Communication and Cell Signaling

Which type of experimental evidence shows that the intrinsic GTPase activity of the Gα subunit is important for terminating effector activation?

#Question id: 1243

#Unit 4. Cell Communication and Cell Signaling

One form of receptor desensitization can be mediated by negative feedback involving phosphorylation of the receptor itself by a kinase activated downstream of a second messenger. The phosphorylated receptor likely:

#Question id: 1242

#Unit 4. Cell Communication and Cell Signaling

Rhodopsin, a light-sensitive GPCR whose role in vision is dependent on its phosphorylation status, is influenced in part by the protein arrestin.  Which of the following is TRUE with regard to rhodopsin and vision?

#Question id: 1241

#Unit 4. Cell Communication and Cell Signaling

Which of the following is a common step in the opening/closing of ion channels by acetylcholine and rhodopsin binding to their receptors?

#Question id: 1239

#Unit 4. Cell Communication and Cell Signaling

GTPases serve in many signal transduction pathways and the presence of GTP or GDP dictates whether the pathway is on or off, respectively. Which of the following statements is TRUE regarding guanine nucleotide exchange factors (GEF) and the role in these signaling pathways?

#Question id: 1238

#Unit 4. Cell Communication and Cell Signaling

Which of the following can lead to loss-of-heterozygosity in a tumor-suppressor gene?

a. deletion of the normal copy                       

b. non dysjunction during mitosis

c. somatic mutation of the normal copy

d. mitotic recombination between a wild-type and mutant allele