Which of the following is the end product of the activation of phospholipase C in the phosphatidylinositol pathway?

• A. cAMP
• B. cGMP
• C. DAG and IP3
• D. Calcium ions

Answer: (C)

The activation of phospholipase C (PLC) in the phosphatidylinositol signaling pathway results in the production of diacylglycerol (DAG) and inositol trisphosphate (IP3). This process begins when a ligand, such as a hormone, binds to a G protein-coupled receptor on the cell membrane. This activation leads to the stimulation of PLC, which hydrolyzes a specific phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP2), resulting in the formation of DAG and IP3.

DAG remains anchored in the cell membrane and serves as a second messenger that activates protein kinase C (PKC), which plays a role in various cellular processes, including growth, differentiation, and secretion. On the other hand, IP3 is released into the cytosol and triggers the release of calcium ions from the endoplasmic reticulum, leading to a rise in intracellular calcium levels that further mediates cellular responses.

This understanding of the phosphatidylinositol pathway highlights the importance of both DAG and IP3 as critical second messengers in cellular signaling processes.