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Archived Comments for: Scale-free flow of life: on the biology, economics, and physics of the cell

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  1. The limits of thermodynamics; the shortcomings of WBE's Kleiber

    Gregory O'Kelly, No affiliation

    27 June 2009

    The author is apparently not aware of the growing amount of data clearly deviating from the predictions of WBE's Kleiber (b=3/4) (DaSilva, Garcia et al. 2006; White, Seymour et al. 2006). These deviations are the result of refinement in metabolic energy measurement, to exclude thermogenesis, and to focus on sugar and oxygen consumption. The exponent 3/4 is an artifact of the data collected by earlier investigators into metabolic energy, like Max Kleiber, who measured this energy in terms of heat energy. That is why metabolic rate is still expressed in calories/sec rather than watts. This has roots in attempts to understand biological energy in terms of thermodynamics. Dr. Kurakin merely introduces the idea that for biology the thermodynamics should be non-equilibrium rather than equilibrium, rather than discarding thermodynamics entirely as inappropriate for understanding what is essentially an electrochemical phenomenon. Statistical mechanics are clearly incommensurable with electromagnetism, being about different things and requiring different mathematics.

    Nor is the author aware that the term "metabolic efficiency" has no place in the equation favored by WBE, who instead assume an efficiency that is not part of the math. If it were, it would appear in the numerator such that, instead of 3/4, the numerator would be (4ME-1)/4ME, where ME is metabolic efficiency, a redox coupling efficiency ratio of amperes. Given this version of the equation, only values like 89 to 100% for ME result in MRs like what WBE show on their preferred graph of mass vs. MR. This eliminates any biological relevance since efficiencies like this are only found in the mechanical world. Biologists take the mechanism metaphor too seriously. Yet, even in mechanics, heat generation is not part of efficiency.

    Dr. Kurakin is encouraged to examine the graph with the X axis as ME, the Y axis as MR, and a DIFFERENT CURVE FOR EACH BIOMASS VALUE in grams. Then he can examine how thermodynamic pressure, given ∆ME [fluctuations in energy supply, the denominator of ME] acts upon biomass through the numerator of ME, to stabilize MR, changing the gram value for biomass. This change can occur as division, growth, or development, as mutation, degeneration, or diminution. These pressures act on biomass against its inertial lagging before the immediacy of ∆ME, to maintain an average MR which, if not attainable, results in appropriate changes in that biomass. For Dr. Kurakin this would be the non-equilibrium whose pressure acts to achieve equilibrium by acting upon the biomass, and it is in this mathematical approach that the numerous issues he declares can be resolved by non-equilibrium considerations, can actually be modeled, including the energetic nature of all biological organization. Aside from this, thermodynamics is useless for biology.

    Competing interests

    None declared