Free activity αX [MU·m-3] is pressure divided by isomorphic force. In the chemical amount format, αX is expressed in units of concentration of X [mol·L-1]. αX is the local concentration in a concentration gradient. If the concentration gradient is collapsed to a boundary of zero thickness in a compartmental system, αX reflects the singularity in the transition between the two phases or compartments.
Abbreviation: αX [MU·m-3]
- Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. https://doi.org/10.26124/bec:2020-0002
- Gnaiger E (1989) Mitochondrial respiratory control: energetics, kinetics and efficiency. In: Energy transformations in cells and organisms. Wieser W, Gnaiger E (eds), Thieme, Stuttgart:6-17. - »Bioblast link«
Isomorphic laws and isomorphic formats
- In ergodynamics, the pressure in a transformation, ΔtrΠX, is the product of free activity times force, ΔtrΠX = αX·ΔtrFX [mol·m-3 · J·mol-1 = J·m-3 = Pa] (Gnaiger 1989).
- Free activity has the unit concentration of the transformation-specific motive unit [MU∙m-3]. Therefore, pressure as the product of isomorphic force and free activity has the unique unit pascal, [Pa] = [J∙m-3] = [J∙MU-1]∙[MU∙m-3].
MitoPedia concepts: MiP concept, Ergodynamics