Question

7 A) Which of the following steps amplify the epinephrine signal response in cells?

1. receptor activation of G protein

2. G protein activation of adenylyl cyclase

3. cAMP activation of PKA

4. PKA phosphorylation of glycogen phosphorylase kinase (GPK)

2, 3, and 4

1, 3, and 4

1 and 3

1 and 4

7 B) Which of the following statements regarding ion channel regulation by GPCRs is FALSE?

Activation of GPCRs in rod cells leads to increased neurotransmitter release.

The muscarinic acetylcholine receptor activates a K+ channel via the G-beta/gamma subunit.

The G-alpha subunit is responsible for activation of PDE in the membrane of rod cells.

Activation of GPCRs in rod cells causes the closing of nonselective cation channels in the membrane.

Answer 1

Answer 7. 1 and 4 are right.

Amplification of epinephrine signal response involves a single active component activating multiple targets to amplify the response. The active receptor of epinephrine activates multiple G (Gas) proteins, and the active PKA initiates kinase cascades by phosphorylating multiple glycogen phosphorylase kinase (GPKs), which in turn phosphorylates multiple glycogen phosphorylase enzymes to continue the signal amplification.

On the other hand, the G protein activates only one Adenylate cyclase , and the cAMP activates only one PKA. None of them amplifies the signal response.

False statement is. Activation of GPCRs in rod cells causes the closing of nonselective cation channels in the membrane.

G proteins activated by rhodopsin do not act directly on ion channels. The closing of cation channels in the rod cell plasma membrane requires changes in the concentration of the second messenger cyclic GMP or cGMP.