Final answer:
The incorrect statement about the hormone-activated phospholipase C pathway is that it involves activation of adenylyl cyclase and increasing levels of cAMP. This is not true, as the pathway actually involves phospholipase C, which leads to the activation of Protein Kinase C (PKC) through other messengers, not cAMP.
Step-by-step explanation:
The statement that is not true for the hormone-activated phospholipase C pathway is: "The pathway involves activation of adenylyl cyclase, increasing levels of cAMP." This is incorrect because in the phospholipase C pathway, the activated G-protein α subunit activates phospholipase C, not adenylyl cyclase. Phospholipase C then leads to the production of inositol triphosphate (IP3) and diacylglycerol (DAG), which mobilize calcium ions and activate Protein Kinase C (PKC), respectively, not cAMP.
Conversely, cAMP is involved when the G-protein α subunit activates adenylyl cyclase. This increases cAMP levels and activates protein kinases, a completely different pathway. Inhibition of adenylyl cyclase affects hormone signaling by preventing the synthesis of cAMP, which is the second messenger in the adenylyl cyclase pathway.
Moreover, cAMP can influence processes including gene transcription and enzyme activation within the cell. To regulate the signal and prevent overproduction of cellular products, cAMP is broken down by phosphodiesterase (PDE).