Cookies help us deliver our services. By using our services, you agree to our use of cookies. More information

Force

From Bioblast
Revision as of 14:00, 2 August 2018 by Gnaiger Erich (talk | contribs)


high-resolution terminology - matching measurements at high-resolution


Force

Description

Forces as defined in physics, F [N ≡ J∙m-1 = m∙kg∙s-2], describe the interaction between particles as vectors with direction of a gradient in space. These forces cause a change in the motion (acceleration) of the particles in the spatial direction of the force. The fundamental forces are the gravitational, electroweak (combining electromagnetic and weak nuclear) and strong nuclear forces. In contrast to the gradient-forces with spatial direction, the compartmental motive forces are stoichiometric potential differences, distinguished as isomorphic motive delta-forces, ∆trF, with compartmental direction of the energy transformation, tr. The delta-forces are expressed in various motive units, MU [J∙MU-1], depending on the energy transformation under study and on the unit chosen to express the motive entity and advancement of the process. For the protonmotive force the proton is the motive entity, which can be expressed in a variety of formats with different MU.

An isomorphic motive force, ΔtrF (intensive quantity), in thermodynamics or ergodynamics is the partial Gibbs (Helmholtz) energy change per advancement of a transformation (tr).

Abbreviation: F; ΔtrF

Reference: Gnaiger_1993_PAC


MitoPedia concepts: MiP concept 

Gibbs energy or Gibbs force?

Publications in the MiPMap
Gnaiger E (2018) Gibbs energy or Gibbs force? Mitochondr Physiol Network 2018-08-02.


Gnaiger E (2018) MiPNet

Abstract: Gibbs energy, G [J], is an extensive quantity, defined relative to a reference state of a system, comparable to altitude [m] defined relative to a reference (altitude at sea level). When a chemical reaction proceeds in a closed isothermal system, the Gibbs energy of the system undergoes a change, drG, [J]. Force is an intensive quantity. An isomorphic force is defined as the partial derivative of Gibbs energy (exergy) per advancement of a transformation, ΔtrF = dtrG/dtrξ. The driving force of a reaction (compare affinity), therefore, is ΔrF = drG/drξ [J·mol-1].


O2k-Network Lab: AT Innsbruck Gnaiger E


Thermodynamic definitions

The Gibbs force of reaction, ΔrFB (or molar Gibbs energy change of reaction of thermodynamics, ΔrGB) can be defined in different and fully consistent ways with units [J·mol-1]. As a prerequisite, the reaction stoichiometry of reaction r must be defined, such that the absolute value of the stoichiometric number of substance B equals 1 (-1 if B is a substrate, +1 if B is a product).
  1. As the difference of stoichiometric electrochemical potentials between final states (products) and initial states (reactants): The stoichiometric electrochemical potential of the substrates in reaction r is Fr,s = Σs -νs · μs; the stoichiometric electrochemical potential of the products in reaction r is Fr,p = Σp νp · μp. Therefore, the chemical force is a difference of stoichiometric electrochemical potentials, ΔrFB = Fr,p - Fr,s
  2. As the sum of stoichiometric electrochemical potentials of all substances involved in reaction r: ΔrFB = Σi νi · μi. Definitions #1 and #2 are fully consistent, which leads to the apparent paradox, that the Δ sign in definition #2 is connected to sum (Σ).
  3. As the partial derivative of Gibbs energy per advancement of reaction: ΔrF = drG/drξ. Use of the same symbol as in definition #1 leads now in the framework of definition #3 to the apparent paradox, that a difference is defined in terms of a differential.


Thermodynamic ignorance

Nicholls DG, Ferguson SJ (2013) Bioenergetics4. Academic Press

"Thermodynamic ignorance is also responsible for some extraordinary errors found in the current literature, particularly in the field of mitochondrial physiology (see Part 3)." - Nicholls, Ferguson (2013): Part 3 (p 27).
  • Part 3 suffers from a confusion between system and process throughout the text.
  • p. 27: Distinction of three types of thermodynamic systems (isolated, closed, open) is insufficient in the context of vectorial metabolism and the protonmotive force. For explaining the nature of the protonmotive force, we need to introduce further categories of systems: homogenous systems, contrinuous systems with gradients, and compartmental (heterogenous) systems with discontinuities across compartmental boundaries.
  • p. 27: Open systems: The oppinion that "classical equilibrium thermodynamics cannot be applid precisely to open systesm because the flow or matter across their boundaries precludes the establishment of a true equilibrium" is in direct contradiction to the presentation of Figure 3.2, which attempts to explain Gibbs energy of reaction by states maintained "by continuously supplying substrate and removing product" (p. 31).
  • p. 28: "It is this displacement from equilibrium that defines the capacity of the reaction to perform useful work." - The term capacity is consfused with the term potential.
  • p. 29: ".. the driving force for a reaction is an increase in entropy .." - Entropy [J·K-1] = driving force?
  • p. 29: "The thermodynamic function that takes account of this enthalpy flow is the Gibbs energy change, ΔG, which is the quantitative measure of the net driving force (at constant temperature and pressure)." - Gibbs energy = net driving force ? There is a lot of confusion to be removed. What is enthalpy flow?
  • p. 29: "The available enery in a gradient of ions is quantified by a further variant of the Gibbs energy change, namely the ion electrochemical gradient" - Electrochemical gradient = Gibbs energy change?
  • p. 31 (Figure 3.2.): This figure presents a inconsistency of units. The content of Gibbs energy (G) kJ is plotted on the Y-axis, and the X-axis is a ratio of mass action ratios (dimensionless ratio). The slope dG/dratio would have the same unit as G [kJ]. Paradoxically, the Figure shows Slope = ΔG (kJ/mol). What is a "slope"? In a meaningful presentation of the concept of molar Gibbs energy change of reaction (Gibbs force [kJ/mol]) in a closed system at constant temperature and pressure, the Gibbs energy should be plotted as a function of advancement of the reaction [mol].
  • p. 32: "Note again that ΔG is a differential .." - As seen in Fig. 3.2, the symbol and meaning of a differential are not understood.


Labels:





HRR: Theory