Once the molecule has been received by the target cell, it triggers a series of steps that help decode the message called the signal transduction pathway. Transduction, which is the second step in cell signaling, is the overall process of a converting a signal to a form that the target cell can understand.
Some signaling pathways produce a metabolic response, in which metabolic enzymes in the cell become more or less active. We can see how this works by considering adrenaline signaling in muscle cells. Adrenaline, also known as epinephrine, is a hormone (produced by the adrenal gland) that readies the body for short-term emergencies. If you’re nervous before a test or competition, your adrenal gland is likely to be pumping out epinephrine.
Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellular response.