Colloquium: Dr. Michael Hinczewski, Case Western Res. Univ.
ABSTRACT: Biological cells have an elaborate machinery for probing their external environment. They gather information about the many small molecules diffusing around them, whether nutrients, or hormones, or toxic agents. This information is conveyed from receptors on the surface of the cell to the interior by a multitude of protein enzymes, catalyzing reactions that add or remove chemical tags from other proteins. These tags are the basic units of biological signaling, analogous to the zeros and ones in which a digital message is encoded in engineered communication systems. But biological circuits are extremely error-prone, distorting the signal through the stochastic nature of protein interactions under constant thermal agitation. So the cell expends enormous amounts of energy on error-correction mechanisms, maintaining the fidelity of the signal. My talk shows how we can understand this energy consumption through the language of thermodynamics, building on recent advances in non-equilibrium statistical physics and information theory. Cellular signaling networks essentially act as "information engines", converting energy from chemical potential reservoirs into useful "work" in the form of accurate information transfer. And just like the second law of thermodynamics constrains the efficiency of mechanical engines, analogous relationships hold for biochemical signaling, putting bounds on the minimum error that can be achieved. We look at the trade-offs between efficiency and power, and the necessity of these biological circuits operating in a highly dissipative, non-equilibrium regime.