Force

high-resolution terminology - matching measurements at high-resolution

Force

Description

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

Abbreviation: Δ_trF

Reference: Gnaiger_1993_PAC

MitoPedia concepts: MiP concept 

Gibbs energy or Gibbs force?

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, d_rG, [J]. Force is an intensive quantity. An isomorphic force is defined as the partial derivative of Gibbs energy (exergy) per advancement of a transformation, Δ_trF = d_trG/d_trξ. The driving force of a reaction (compare affinity), therefore, is Δ_rF = d_rG/d_rξ [J·mol^-1].

• O2k-Network Lab: AT Innsbruck Gnaiger E

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.

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