Final answer:
RKT activates PI3K to produce diacylglycerol (DAG) and inositol triphosphate (IP3) in the plasma membrane.
Step-by-step explanation:
RKT, or receptor tyrosine kinase, activates PI3K, which produces two second messengers in the plasma membrane: diacylglycerol (DAG) and inositol triphosphate (IP3). Diacylglycerol (DAG) remains in the plasma membrane and activates protein kinase C (PKC), which then phosphorylates serine and threonine residues in its target proteins. IP3 diffuses into the cytoplasm and binds to ligand-gated calcium channels in the endoplasmic reticulum, releasing calcium ions (Ca²+) that continue the signal cascade.