Subcellular Systems Observe Onsager Reciprocity

The complexity of prokaryotic and, exceedingly, of eukaryotic cells, challenges the implementation of methodologies to determine causality and quantify intracellular dynamics. Although stochastic thermodynamics can be used to effectively quantify the energetics of single proteins or complexes, there is no statistical approach to determine the macrostate of a whole cell from its subcellular microstates. Onsager reciprocity, a coupling between thermodynamic flows, could potentially be leveraged to quantify and to establish causality among subcellular systems. A prototypical thermodynamic profile of the cell is formulated as a model system to enable representation of its sub systems as force-driven thermodynamic flows. Onsager reciprocity is validated on the bacterial flagellum and ATP synthase. It is then tested on the putative coupling between the contractile ring and treadmilling of the cytoskeleton in bacterial binary fission and eukaryotic cytokinesis, with opposite outcomes. All thermodynamic flows and forces are formulated to comply with their canonical definitions.