Answer:
b. Overall process of translating information from an extracellular messenger into cellular changes.
Step-by-step explanation:
Signal transduction is the process of translation and amplification of an extracellular signal into an intracellular signal. This generated intracellular signal then affects some functions in the cell. The whole sequence is called signal transduction.
For example, when a signaling molecule binds to the G protein-linked receptor present in the plasma membrane, the G protein is activated. The activated G protein triggers the synthesis of cAMP by activating the enzyme adenylyl cyclase. The function of cAMP is to activate certain protein kinases which in turn generate the physiological response in cells by phosphorylation of target proteins.