Advanced Placement (AP) Biology Practice Exam

Which of the following lists the correct order of stages in cell signaling?

1. Transduction, reception, response

2. Reception, transduction, response

3. Response, reception, transduction

4. Transmission, reception, response

The correct answer is: Reception, transduction, response

The correct order of stages in cell signaling is reception, transduction, and response. In the first stage, reception, a signaling molecule, such as a hormone or neurotransmitter, binds to a specific receptor on the surface of a target cell. This interaction is crucial as it initiates the signaling process. Following that is the transduction stage, where the cell converts the received signal into a form that can bring about a cellular response. This often involves a series of complex biochemical events, including the activation of a cascade of proteins, second messengers, or other intermediary molecules that amplify the signal and carry it through the cell. Finally, during the response stage, the cell executes a function based on the signal received, which can include changes in gene expression, alterations in metabolism, or responses such as growth, movement, or apoptosis. Other listed options present the stages out of order, which would disrupt the logical progression of how cells communicate and respond to their environment. Reception must occur before transduction can take place, and only after that can a cellular response be generated.