Advanced Placement (AP) Biology 2025 – 400 Free Practice Questions to Pass the Exam

Signal transduction is the process that encompasses the transmission of a stimulus leading to a specific cellular response. This process typically involves the reception of a signaling molecule, such as a hormone or neurotransmitter, by a receptor on the surface of a target cell. Upon binding, this receptor undergoes a conformational change that activates a cascade of downstream events within the cell, often involving secondary messengers.

These cascades can alter gene expression, modulate enzyme activity, or change the characteristics of the cell membrane, thereby allowing the cell to respond appropriately to the original stimulus. Signal transduction pathways are crucial for allowing cells to communicate with each other and adapt to changes in their environment, making them fundamental to many biological processes, including growth, immune responses, and metabolism.

Hormone synthesis is related but focuses on the production of hormones rather than their action within target cells. Catabolic metabolism refers to the breakdown of molecules to release energy but does not specifically pertain to the transmission of stimuli. Cellular respiration involves the process by which cells convert biochemical energy from nutrients into ATP, and while it can be influenced by signaling pathways, it is not directly involved in the transmission of a stimulus to a cellular response.