Acetylcholine Acts at a GPCR on Heart Muscle to Make

Essay

Acetylcholine acts at a GPCR on heart muscle to make the heart beat more slowly.It does so by ultimately opening K⁺ channels in the plasma membrane (as diagrammed in Figure 16-51), which decreases the cell's excitability by making it harder to depolarize the plasma membrane.
Indicate whether each of the following conditions would increase or decrease the effect of acetylcholine.
A.addition of a drug that stimulates the GTPase activity of the Gα subunit
B.mutations in the K⁺ channel that keep it closed all the time
C.modification of the Gα subunit by cholera toxin
D.a mutation that decreases the affinity of the βγ complex of the G protein for the K⁺ channel
E.a mutation in the acetylcholine receptor that prevents its localization on the cell surface
F.adding acetylcholinesterase to the external environment of the cell