]>
2022-01-24T18:16:46+01:00
Gnaiger 2018 MiPschool Tromso A2
0
en
MitoEAGLE
Oral
A2
Peter Mitchell's protonmotive force is one of the most fundamental concepts in biology [1]. The catabolic reactions of mitochondrial electron transfer (ET) are coupled to vectorial translocation of protons at three coupling sites, which are the proton pumps of the ET system (ETS): respiratory Complexes CI, CIII, and CIV. The driving force of the ETS in the catabolic (k) reaction expressed as O<sub>2</sub> consumption is the Gibbs force of reaction, Δ<sub>k</sub>''F''<sub>O2</sub>, which is typically in the range of -460 to -480 kJ/mol (~ -1.2 V). The Gibbs force is an ''[[isomorphic]]'' [[force]], also known as a generalized force (the negative [[affinity]] of chemical reactions in nonequilibrium thermodynamics) [2]. Confusion is caused by the failure of terminological distinction between Gibbs energy change of reaction, Δ<sub>r</sub>''G'' [J], and Gibbs force equal to the partial Gibbs energy change per [[advancement]] of reaction [3]. For the protonmotive force the proton is the motive entity, which can be expressed in a variety of formats with different [[motive unit]]s, MU.
A problem in the bioenergetic literature is the confusion between proton gradients (vector analysis in continuous systems) and differences of proton concentrations (activities) between compartments separated by a semipermeable membrane (vectorial analysis in compartmental systems). Fundamental insights are gained by distinguishing between vectoral forces and flows, versus vectorial forces and flows. This is explained by (''1'') appreciation of Ludwig Bolzmann's impact on today's scientific world-view, and (''2'') an explanation of the relevance of Einstein's diffusion equation for understanding the relation between protonmotive force and metabolic flux. Boltzmann committed suizide in 1906, one year after Einstein applied his particle concept of physics successfully to explain diffusion on the basis of Brownian motion [4]. At steady-state the local concentration along a diffusion gradient changes as a function of the chemical potential gradient, whereas the concentration gradient is constant along the diffusion path (in a homogenous medium at steady state; Fick's law of diffusion). Therefore, the concentration gradient of a continous system can be replaced by the concentration difference in a discontinuous system. Here is where some simple equations help. Thermodynamics and ergodynamics are inherently ''mathematical'', but relationships expressed in well defined terms rather than mathematical equations are the basis of understanding. Development of such understanding and immediate applications to plan and interpret experimental results on mitochondrial respiratory control, however, is greatly aided by making us familiar with a large number of fundamental physicochemical terms (or concepts) and their (mostly simple) mathematical relationships. But why should we be interested in the Gas law (the Gas equation)?
[[Gnaiger E]]
Force
Protonmotive force
Flux
[[File:Erich Gnaiger.jpg|left|90px|Erich Gnaiger]] The protonmotive force and respiratory control. 1. Coupling of electron transfer reactions to vectorial translocation of protons. 2. From Einstein’s diffusion equation on gradients to Fick’s law on compartments.
Theory
Respiration
mt-Membrane potential
2018
2020-02-13T12:59:07Z
2458893.0410532
Gnaiger 2018 MiPschool Tromso A2