Connectivity diagram of key components in the EGFR signaling pathway. Each gate represents a series of reactions resulting in the production of the substance connected to the curved side. The substances connected to the flat side of a gate are the inputs. The initial inputs are set by the state of EGF species (internal and external). The connections show all paths between key components in the EGFR signaling pathway. Red connections indicate inhibition and all others activation. A connection is colored black or green if inactivation of the input disables activation of the output. Disconnection of one of the substances in orange or red does not affect activity of the output. The diagram clearly shows which paths carry signal that do not affect the overall activation of the component (red and orange wires), and which paths carry signals that are necessary to activate the component (green and black wires).