Question

PI 3-kinase phosphorylates the inositol head groups of phospholipids at the 3 position of the ring so that they can be cleaved by phospholipase C to produce IP3. True or False?

1) True
2) False

Answer 1

False. PI 3-kinase phosphorylates the inositol head groups of phospholipids, but it does not directly cleave them. Phospholipase C is responsible for cleaving phosphatidylinositol 4,5-bisphosphate (PIP2) to produce inositol trisphosphate (IP3) and diacylglycerol (DAG) as second messengers.

Step-by-step explanation:

False. PI 3-kinase phosphorylates the inositol head groups of phospholipids at the 3 position of the ring, but it does not directly cleave them. Instead, it adds a phosphate group to the inositol head group, forming phosphatidylinositol 3-phosphate (PI3P). Phospholipase C (PLC) is responsible for cleaving phosphatidylinositol 4,5-bisphosphate (PIP2) to produce inositol trisphosphate (IP3) and diacylglycerol (DAG) as second messengers.

PI 3-kinase and PLC play different roles in cellular signaling, with PI 3-kinase involved in signaling pathways related to cell growth, survival, and proliferation, while PLC is involved in calcium signaling and the activation of PKC.

For example, IP3 generated by PLC can bind to receptors on the endoplasmic reticulum and release calcium ions into the cytoplasm, leading to various cellular responses.