Signaling pathways are complex networks of proteins and molecules that transmit signals from a cell's surface to its interior. These pathways help cells respond to external stimuli, such as hormones or growth factors, and play a crucial role in regulating various cellular processes, including growth, differentiation, and metabolism. When a signal binds to a receptor on the cell membrane, it triggers a series of biochemical reactions within the cell. This cascade of events often involves secondary messengers, such as cAMP or calcium ions, which amplify the signal and lead to specific cellular responses. Understanding these pathways is essential for developing targeted therapies in diseases like cancer and diabetes.