A signal molecule binds to a receptor.
A conformational change in the signal-receptor complex activates an enzyme.
Second messenger molecules are released.
Protein kinases are activated.
Target proteins are phosphorylated.
Signal transduction can be defined as the process in which a physical or chemical signal is transmitted through a cell as a series of molecular events inform of protein phosphorylation are catalyzed by protein kinase and this ultimately result into a cellular response. However, the protein that is responsible for the detection of stimuli is commonly refers to as receptors or sensor.