2. Here is the figure of the G protein couple receptor (GPCR)activation of K+ channels in the pacemaker cells of the heart(right).

Under which of the following scenarios would the effect ofacetylcholine be enhanced (thus resulting in slowing the heart beatrate)? For those scenarios which do not enhance the effect ofacetylcholine, explain why it would not do so. (3 pts)

a. Changes in the protein structure of the K⁺ channelwhich would decrease the interaction of the activated bg complexand the K⁺ channel.

b. An extremely high affinity of the G protein for GDP.

c. GTP molecules which are not hydrolysable

d. Changes in the receptor protein which decreases the affinityof the receptor for acetylcholine

3. Compare and contrast cell signaling via GTP-binding proteins(molecular switches) and signaling through the cortisol activationof a transcription factor (4 pts).

4. Many extracelluar signals which promote survival and growthwork through RTKs. The activated AKt (also called protein kinase B)promotes cells survival through its interaction with Badand Bcl2. Akt is able to phosphorylate Bad whichinactivates it (thus it no longer will promote cell suicide).

Which of the following scenarios arefalse? If they are false explain why they are false.

a. When Akt is activated, its major function is to phosphorylateother proteins

b. When there are signals for cell death, Akt will bephosphorylated:

c. When Akt is activated, it will inhibit Bcl2:

d. Akt is activated when it is phosphorylated.