Final answer:
In the calmodulin activation pathway, diacylglycerol (DAG) remains membrane-bound and activates protein kinase C (PKC) to phosphorylate target proteins.
Step-by-step explanation:
In the calmodulin activation pathway, the component that remains membrane-bound is diacylglycerol (DAG). After being formed through the cleavage of PIP₂ by phospholipase C, DAG stays in the plasma membrane and activates protein kinase C (PKC), which then phosphorylates serine and threonine residues in target proteins. This activation pathway allows for the propagation of the signal cascade.