Advanced Placement (AP) Biology Practice Exam

What role does cAMP play in signal transduction?

1. It acts as a primary signaling hormone

2. It facilitates intra-cellular signal transduction as a secondary messenger

3. It directly binds to DNA for transcription regulation

4. It serves as a storage molecule for genetic information

The correct answer is: It facilitates intra-cellular signal transduction as a secondary messenger

cAMP, or cyclic adenosine monophosphate, functions as a secondary messenger in the process of signal transduction. When an extracellular signaling molecule, such as a hormone or neurotransmitter, binds to a receptor on the surface of a cell, it can trigger a cascade of intracellular events. This often involves the activation of an enzyme called adenylate cyclase, which converts ATP into cAMP. The increase in cAMP levels within the cell amplifies the signal received from the outside, enabling a rapid response. cAMP interacts with various target proteins inside the cell, such as protein kinases, specifically protein kinase A (PKA). Upon activation, PKA can then phosphorylate different proteins, leading to changes in their activity and ultimately affecting cellular processes such as metabolism, gene expression, and cell division. This capacity to relay signals from the cell membrane into the interior of the cell underscores the essential role of cAMP as a secondary messenger, linking the first signal (the hormone) to a wide array of intracellular responses. The other options do not accurately reflect the role of cAMP: - It does not act as a primary signaling hormone, as it does not directly initiate the signaling event but rather transmits and amplifies a signal that has