Question

The second messengers diacylglycerol and inositol trisphosphate are synthesized simultaneously from a cell-membrane phospholipid, ______ by the catalytic action of activated ________ , a membrane-assoicated enzyme.

Answer 1

Diacylglycerol and inositol trisphosphate are synthesized from phosphatidylinositol bisphosphate (PIP₂) by the enzyme phospholipase C, leading to the activation of protein kinase C and the release of Ca²⁺ ions.

Step-by-step explanation:

The two second messengers, diacylglycerol (DAG) and inositol trisphosphate (IP3), are synthesized from a cell-membrane phospholipid known as phosphatidylinositol bisphosphate (PIP₂). The enzyme responsible for this is phospholipase C (PLC), which becomes activated through the interaction with a hormone-bound receptor and a stimulatory G-protein. Once activated, PLC cleaves PIP₂ to produce DAG, which stays in the membrane to activate protein kinase C (PKC), and IP3 which diffuses into the cytoplasm to bind to receptors on the endoplasmic reticulum, releasing Ca²⁺ ions that further propagate the signal within the cell.