Advanced Placement (AP) Biology Practice Exam

What is the key characteristic of autocrine signaling?

1. It requires close contact between cells

2. It involves signaling to other organisms

3. A cell changes in response to its own secreted signals

4. It involves long-distance communication between distant cells

The correct answer is: A cell changes in response to its own secreted signals

The key characteristic of autocrine signaling is that a cell responds to its own secreted signals. This form of signaling allows a cell to produce signaling molecules that bind to receptors on its own surface, triggering a response that can influence its behavior, growth, or other functions. This mechanism is significant in processes such as immune responses, where certain cells secrete cytokines that act on themselves to enhance their activity. In contrast, mechanisms requiring close contact between cells refer to juxtacrine signaling, which involves direct cell-to-cell communication. The idea of signaling to other organisms pertains more to interorganismal signaling, which is not a feature of autocrine signaling. Lastly, long-distance communication is characteristic of endocrine signaling, where hormones travel through the bloodstream to distant target cells, which is fundamentally different from the localized effect of autocrine signaling.