[Campbell Biology P.272] Based on Figure 11.11 and the accompanying text, what would be the ... | Practice Question

Based on Figure 11.11 and the accompanying text, what would be the most likely consequence if a molecule that completely inactivates phosphodiesterase were introduced into a cell stimulated by epinephrine?

  • A: The conversion of ATP to cAMP would cease, leading to a rapid decrease in cAMP levels.
  • B: cAMP levels would remain elevated for a prolonged period, leading to extended activation of protein kinase A and its downstream effects.
  • C: Epinephrine would no longer be able to bind to its GPCR, preventing signal initiation.
  • D: The activated protein kinase A would dephosphorylate various other proteins, turning off the signal.

Explanation

The text states that phosphodiesterase converts cAMP to AMP, inactivating cAMP. If phosphodiesterase is inhibited, cAMP would not be broken down as quickly, leading to its sustained high levels. Elevated cAMP levels usually activate protein kinase A, which then phosphorylates downstream targets, prolonging the cellular response.