Free activity

high-resolution terminology - matching measurements at high-resolution

Free activity

Description

Free activity α_X [MU·m^-3] is pressure divided by isomorphic force. In the chemical amount format, α_X is expressed in units of concentration of X [mol·L^-1]. α_X is the local concentration in a concentration gradient. If the concentration gradient is collapsed to a boundary of zero thickness in a compartmental system, α_X reflects the singularity in the transition between the two phases or compartments.

Abbreviation: α_X [MU·m^-3]

Reference:

• Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5^th 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, Δ_trΠ_X, is the product of free activity times force, Δ_trΠ_X = α_X·Δ_trF_X [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