**Question:** PI P2 is cleaved into IP3 and DAG by -

**Core Concept:** Phosphoinositide signaling is a crucial pathway involved in cellular processes such as cell adhesion, migration, and vesicular transport. Phosphoinositides are a group of lipid molecules that play a role in regulating the structure and function of the plasma membrane.

**Why the Correct Answer is Right:** Phosphatidylinositol-4,5-bisphosphate (PI P2) is cleaved into inositol trisphosphate (IP3) and DAG (diacylglycerol) by phospholipase C (PLC). PLC is a group of enzymes that catalyze the hydrolysis of phosphoinositides and other phospholipids, producing inositol phosphates and diacylglycerol.

**Why Each Wrong Option is Incorrect:**

A. Phosphatidylinositol-3,4,5-trisphosphate (PI P3) is not the correct phosphoinositide involved in this process.
B. Phosphatidylinositol-4-phosphate (PI P4) is another phosphoinositide, but it is not the correct substrate for PLC in this context.
C. Phosphatidylinositol-3,4-bisphosphate (PI P2) is not the correct phosphoinositide involved in this process.
D. Phosphatidylinositol-5-phosphate (PI P5) is not the correct phosphoinositide involved in this process.

**Clinical Pearls:**

1. Phosphatidylinositol-4,5-bisphosphate (PI P2) is a crucial substrate for PLC in various cellular processes, including Ca2+ release from intracellular stores and activation of protein kinase C.
2. PLC is activated by various signaling molecules, such as receptor-bound G proteins and tyrosine kinase receptors, leading to the activation of downstream signaling pathways.
3. Inositol phosphates and diacylglycerol generated by PLC serve as second messengers, regulating various cellular processes, including cell proliferation, differentiation, and apoptosis.

**Correct Answer:** D. Phosphatidylinositol-4,5-bisphosphate (PI P2) is cleaved into inositol trisphosphate (IP3) and diacylglycerol (DAG) by phospholipase C (PLC).

**Why the Correct Answer is Right:** PLC is activated by various signaling molecules, such as receptor-bound G proteins and tyrosine kinase receptors, leading to the activation of downstream signaling pathways. PI P2 is the correct phosphoinositide involved in this process, as it is hydrolyzed by PLC to produce IP3 and DAG, which serve as second messengers in cellular signaling pathways.

**Why Each Wrong Option is Incorrect:**

A. Phosphatidylinositol-3,4,5-trisphosphate (PI P3) is not the correct phosphoinositide involved in this process. PI P3 is involved in regulating cell growth and survival pathways, not the pathways mentioned