Signal transduction is the process by which cells respond to external signals, such as hormones or nutrients. When a signal molecule, like a hormone, binds to a receptor on the cell's surface, it triggers a series of events inside the cell. This can lead to changes in gene expression, enzyme activity, or even cell movement, allowing the cell to adapt to its environment. The pathway of signal transduction often involves a cascade of proteins that relay the signal from the receptor to the target within the cell. These proteins, known as signaling molecules, can amplify the signal, ensuring a strong response. Ultimately, signal transduction is crucial for maintaining cellular functions and communication.