Question

___activates G-protein gated potassium channel resulting in membrane hyperpolarization.

• A. α₁ adrenergic receptor
• B. α₂ adrenergic receptor
• C. β₁ adrenergic receptor
• D. β₂ adrenergic receptor

Answer 1

The Correct Option is B

To solve this question, we need to understand the function of the different adrenergic receptors in the context of G-protein coupled receptor signaling. The question is asking which receptor activates the G-protein gated potassium channel, resulting in membrane hyperpolarization.

Here is a brief explanation of each option:

1. α₁ adrenergic receptor: This receptor is primarily linked to the G_q protein and typically leads to the activation of phospholipase C, resulting in increased intracellular calcium concentrations, causing smooth muscle contraction. It does not activate potassium channels.
2. α₂ adrenergic receptor: This receptor is associated with the G_i type of G-protein. Activation of the α₂ receptor inhibits adenylyl cyclase, decreases cAMP levels, and opens G-protein gated potassium channels, leading to membrane hyperpolarization.
3. β₁ adrenergic receptor: Typically coupled with G_s proteins, this receptor stimulates adenylyl cyclase and increases cAMP levels, which mainly leads to increased heart rate and force of contraction. It does not directly activate potassium channels leading to hyperpolarization.
4. β₂ adrenergic receptor: Similar to β₁, this receptor is also linked to G_s proteins and operates through increases in cAMP levels, causing smooth muscle relaxation but not specifically by activating potassium channels.

Since the α₂ adrenergic receptor is the only option that is coupled to the G_i protein, which results in the activation of G-protein gated potassium channels leading to hyperpolarization, the correct answer is:

Correct Answer: α₂ adrenergic receptor