[Campbell Biology P.274] Which of the following correctly describes the roles of inositol tr... | Practice Question

Which of the following correctly describes the roles of inositol trisphosphate IP3 and diacylglycerol DAG in the signaling pathway depicted in Figure 11.14?

  • A: Both IP3 and DAG are primary messengers that bind to the cell surface receptor.
  • B: IP3 primarily activates protein kinase C, while DAG causes the release of Ca2+ from the ER.
  • C: IP3 directly cleaves PIP2 into DAG, and DAG acts as a second messenger to open ER calcium channels.
  • D: Both IP3 and DAG are second messengers, with IP3 causing the release of Ca2+ from the ER, and DAG functioning as a second messenger in other pathways.
  • E: DAG is a first messenger, and IP3 is a second messenger that activates mitochondrial Ca2+ pumps.

Explanation

In the signaling pathway shown in Figure 11.14, phospholipase C cleaves PIP2 into two second messengers: IP3 and DAG. IP3 specifically diffuses to and opens IP3-gated calcium channels in the ER membrane, leading to Ca2+ release into the cytosol. DAG functions as a second messenger in other signaling pathways, often activating protein kinase C.