What term describes the receptor's propagation of its regulatory signal into the target cell?

• A. Recognition
• B. Transduction
• C. Activation
• D. Transmission

Answer: (B)

Transduction describes how a receptor’s message is carried inside the cell and converted into an intracellular response. When a ligand binds, the receptor undergoes a change that starts a cascade of intracellular signaling proteins and second messengers. This relay and amplification inside the cell transforms the external signal into actions such as enzyme activity changes or altered gene expression. Recognition is just the initial binding step, not the internal relay. Activation refers to the receptor becoming active, but the term transduction specifically captures the propagation and processing of the signal within the cell. Transmission isn’t the standard term for this intracellular relay.