Gnaiger 2018 MiPschool Tromso A2

The protonmotive force and respiratory control. 1. Coupling of electron transfer reactions to vectorial translocation of protons. 2. Gradients from Fick’s law to Einstein’s diffusion equation.

Link: MitoEAGLE

Gnaiger E (2018)

Event: MiPschool Tromso-Bergen 2018

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 O₂ consumption is the Gibbs force of reaction, Δ_kF_O2, 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. Confusion is caused by the failure of terminological distinction between Gibbs energy change of reaction, Δ_rG [J], and Gibbs force equal to the partial Gibbs energy change per advancement of reaction [2]. For the protonmotive force the proton is the motive entity, which can be expressed in a variety of formats with different motive units, 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.

• Keywords: Force, Protonmotive force, Flux • Bioblast editor: Gnaiger E

Affiliations and support

1. D. Swarovski Research Lab, Dept. Visceral, Transplant Thoracic Surgery, Medical Univ Innsbruck
2. Oroboros Instruments, Innsbruck, Austria

Contribution to COST Action CA15203 MitoEAGLE, supported by COST (European Cooperation in Science and Technology), and K-Regio project MitoFit.

References

1. Mitchell P (1966) Chemiosmotic coupling in oxidative and photosynthetic phosphorylation. Glynn Research, Bodmin. Biochim Biophys Acta Bioenergetics 1807:1507-38.

1. Gnaiger E (1993) Nonequilibrium thermodynamics of energy transformations. Pure Appl Chem 65:1983-2002. - »Bioblast link«

1. Gnaiger E (2018) Gibbs energy or Gibbs force? Mitochondr Physiol Network 2018-08-07. - »Bioblast link«

Questions

A: Convert the molar format of the Gibbs force of reaction, Δ_kF_nO2 [kJ/mol], into the electrical format, Δ_kF_eO2 [V].

1. Which physicochemical constant is required?
2. What is the meaning of the symbol z_O2?
3. How are the units of electric energy [J] and electric force [V] related?
4. Express -460 kJ/mol O₂ as electrical force in units of volt [V].
5. Why should we do that?

Labels: MiParea: Respiration 

Regulation: mt-Membrane potential 

HRR: Theory  Event: A4, Oral