Ip3
IP3 (Inositol 1,4,5-trisphosphate) is a cleavage product of phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 is a phospholipid molecule cleaved into inositol 1,4,5-trisphosphate and diacylglycerol (DAG) by phospholipase C after hormone binding to the receptor. Inositol 1,4,5-trisphosphate binds to IP3receptor which results to the release of calcium from the calcium pumps.
Also see cell and membrane transport