Question

Determine the second messenger involved in mobilizing \(\mathrm{Ca^{2+}}\) from the endoplasmic reticulum?

• A. cAMP
• B. DAG
• C. IP\(_3\)
• D. cGMP

Hint:

In the PIP\(_2\) pathway, \[ \boxed{ \mathrm{PIP_2} \rightarrow \mathrm{IP_3}+ \mathrm{DAG} } \] where \[ \boxed{ \mathrm{IP_3} \rightarrow \text{Releases } \mathrm{Ca^{2+}} \text{ from the ER} } \] and \[ \boxed{ \mathrm{DAG} \rightarrow \text{Activates Protein Kinase C (PKC).} } \]

Answer 1

The Correct Option is C

Step 1: Recall the IP\(_3\)--DAG signaling pathway. Activation of phospholipase C hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP\(_2\)) into \[ \boxed{\mathrm{IP_3} \text{ and DAG}.} \]

Step 2: Identify the messenger responsible for calcium release. IP\(_3\) binds to IP\(_3\) receptors present on the endoplasmic reticulum and opens calcium channels. This releases stored \[ \mathrm{Ca^{2+}} \] into the cytoplasm. Hence, \[ \boxed{\mathrm{IP_3}} \] is the correct answer. Therefore, \[ \boxed{(C)} \] is the correct answer.