Final answer:
Phospholipase C (E) is not a secondary messenger but an enzyme that generates secondary messengers. cAMP, DAG, IP3, and Ca2+ are examples of secondary messengers involved in cellular signal transduction.
Step-by-step explanation:
Secondary messengers are intracellular signaling molecules released by the cell to trigger physiological changes such as proliferation, differentiation, migration, survival, and apoptosis. They are a component of signal transduction cascades and are responsible for amplifying the signal from a neurotransmitter or hormone. cAMP, DAG, IP3, and Ca2+ are typical secondary messengers within cells. Phospholipase C (PLC), on the other hand, is an enzyme that generates secondary messengers (the cleaved products IP3 and DAG from PIP2) rather than functioning as a secondary messenger itself.
PLC's role is thus upstream of the generation of secondary messengers in the signaling pathways within a cell. When PLC is activated, it converts PIP2 into IP3 and DAG, which then proceed to act as secondary messengers, with IP3 causing the release of Ca2+ from the endoplasmic reticulum and DAG activating protein kinase C (PKC).