Advanced Placement (AP) Biology Practice Exam

What are second messengers responsible for in cellular signaling?

1. Creating proteins

2. Sending messages throughout the cells

3. Decomposing waste

4. Storing nutrients

The correct answer is: Sending messages throughout the cells

Second messengers play a crucial role in cellular signaling by amplifying and transmitting signals received by cell surface receptors to target molecules inside the cell. When a signaling molecule, such as a hormone or neurotransmitter, binds to a receptor on the cell membrane, it triggers a cascade of events that leads to the production of second messengers. These small molecules, such as cyclic AMP (cAMP) or calcium ions, serve to relay the signal internally, facilitating various cellular responses, including gene expression, metabolism adjustments, and ion channel regulation. This process allows cells to respond quickly and effectively to external signals, ensuring appropriate physiological responses. Second messengers effectively "send messages" within the cell, coordinating various biochemical pathways and enabling the cell to adapt to its environment.