Emergent properties of networks of biological signaling pathways

Many distinct signaling pathways allow the cell to receive, process, and re spond to information. Often, components of different pathways interact, res ulting in signaling networks. Biochemical signaling networks were construct ed with experimentally obtained constants and analyzed by computational met hods to understand their role in complex biological processes. These ner:wo rks exhibit emergent properties such as integration of signals across multi ple time scales, generation of distinct outputs depending on input strength and duration, and self-sustaining feedback Loops. Feedback can result in b istable behavior with discrete steady-state activities, well-defined input thresholds for transition between states and prolonged signal output, and s ignal modulation in response to transient stimuli. These properties of sign aling networks raise the possibility that information for "learned behavior " of biological systems may be stored within intracellular biochemical reac tions that comprise signaling pathways.