Cell signaling pathways often contain feedback loops where proteins are produced that regulate signaling. While feedback regulatory mechanisms are commonly found in signaling pathways, there is no example available in the literature which is simple enough to be presented in an ndergraduate control class. This paper presents a simulation study of cell signaling in liver cells where it is shown that the cellular regulatory response can be represented by linear transfer functions for certain levels of stimulation.
A.K. Singh, A. Jayaraman, and J. Hahn. "A Case Study of Representing Signal Transduction in Liver Cells as a Feedback Control Problem"
Chemical Engineering Education 41, No. 3, pp. 177-182 (2007)