Which ONE of the following statements is MOST ACCURATE?
以下哪个说法最准确？

Question

Which ONE of the following statements is MOST ACCURATE?
以下哪个说法最准确 ？

BlackTom AI · Accepted Answer

Metabotropic receptors act through G-proteins to produce multiple downstream effects: direct modulation of ion channels, activation of adenylyl cyclase, and activation of phospholipase C (PLC).

1) Relevant knowledge points and concepts
- Metabotropic receptors are G-protein‑coupled receptors (GPCRs) that signal via heterotrimeric G proteins (Gα, Gβγ).
- Different Gα subtypes produce distinct effects: Gαs stimulates adenylyl cyclase (AC) → increases cAMP → activates PKA; Gαi inhibits AC → lowers cAMP; Gαq/11 activates PLCβ → hydrolyzes PIP2 into IP3 and DAG, where IP3 releases Ca2+ from the endoplasmic reticulum and DAG activates PKC.
- Gβγ subunits (and sometimes downstream second messengers) directly or indirectly modulate ion channels (e.g., Gβγ opens G-protein‑gated inwardly rectifying K+ channels, GIRKs; Gβγ and second messengers can inhibit voltage‑gated Ca2+ channels).

2) Step‑by‑step reasoning
- Option: “Metabotropic receptors may modulate ion‑channels via G‑proteins.” Mechanism: upon activation, Gβγ binds GIRK channels causing K+ efflux and hyperpolarization (example: M2 muscarinic receptors in heart), or downstream kinases phosphorylate channels to alter conductance.
- Option: “Metabotropic receptors may activate Adenylyl Cyclase via G‑proteins.” Mechanism: Gαs binds and activates AC → ATP converted to cAMP → PKA activation and phosphorylation of targets (classic β‑adrenergic signaling).
- Option: “Metabotropic receptors may activate Phospholipase C (PLC) via G‑proteins.” Mechanism: Gαq activates PLCβ → PIP2 → IP3 + DAG → IP3‑mediated Ca2+ release and DAG activation of PKC (example: M1 muscarinic receptors).

3) Calculations
- No numerical calculations required; pathways described qualitatively.

4) Why the correct answer is correct
Each listed molecular outcome is a well‑established canonical GPCR signaling pathway. GPCRs use different G protein subunits to produce the three mechanisms described.

5) Why other options are incorrect
There are no incorrect choices among the specific mechanistic statements; each describes a valid GPCR/G‑protein mediated effect. Therefore none of the three mechanistic options is wrong.

6) Conclusion
All three specific statements about metabotropic (G‑protein‑coupled) receptor signaling are accurate; hence the most accurate choice is “All of the options are correct,” which matches the provided answer.

Which ONE of the following statements is MOST ACCURATE? 以下哪个说法最准确？单项选择题

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Which ONE of the following statements is MOST ACCURATE? 以下哪个说法最准确 ？单项选择题