Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events.
When signalling pathways interact with one another, they form networks, which allow cellular responses to be coordinated. At the molecular level, this leads to changes in the transcription or translation of genes, and post translational and conformational changes in proteins, as well as changes in their location.
These molecular events are the basic mechanisms controlling cell growth, proliferation, metabolism and many other processes. They also regulate cell communication in a wide variety of ways.