Final answer:
IP3 and DAG are second messengers produced by the cleavage of PIP2 by phospholipase C. IP3 triggers the release of Ca²⁺ from the ER, while DAG remains in the membrane, activating PKC and reinforcing Ca²⁺ signaling.
Step-by-step explanation:
When comparing inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG), it's essential to understand their formation and function as second messengers in signal transduction. The enzyme phospholipase C cleaves PIP2 into IP3 and DAG. IP3 diffuses into the cytoplasm and binds to ligand-gated calcium channels in the endoplasmic reticulum to release Ca²⁺, further propagating the cellular signal.
Conversely, DAG remains in the plasma membrane and has dual roles: it activates protein kinase C (PKC) and can facilitate the opening of Ca²⁺ channels, thus reinforcing the pathway initiated by IP3. PKC then phosphorylates serine and threonine residues on numerous proteins, modifying their activity and effecting cellular responses to various stimuli.