General Principles of Cellular Signaling

Signaling is a process by which information received from one cell is converted into a response by another cell. 

The signaling cell produces and ordinarily secretes a ligand, which travels to the target cell. 

Receptors displayed by the target cell bind the ligand and transduce the signal into a second messenger or a series of biochemical events that mediate the response by the target cell. 

The signaling cell may be located far away from or adjacent to the target cell in some cases, a cell signals itself 

The events set in motion by ligand binding to the receptor represent the signaling pathway. 

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