Thermodynamics of organisms in the context of dynamic energy budget theory
Sousa, T., Mota, R., Domingos,T. and Kooijman, S. A. L. M. 2006.
Thermodynamics of organisms in the context of dynamic energy budget theory
Physical Review E, 74: 05 1901, 1-15
Abstract
We carry out a thermodynamic analysis to an organism. It is applicable
to any type of organism because (1) it is based on a thermodynamic
formalism applicable to all open thermodynamic systems and (2) uses a
general model to describe the internal structure of the organism the
dynamic energy budget DEB model. Our results on the thermodynamics of
DEB organisms are the following. (1) Thermodynamic constraints for the
following types of organisms: (a) aerobic and exothermic, (b) anaerobic
and exothermic, and (c) anaerobic and endothermic; showing that
anaerobic organisms have a higher thermodynamic flexibility. (2) A way
to compute the changes in the enthalpy and in the entropy of living
biomass that accompany changes in growth rate solving the problem of
evaluating the thermodynamic properties of biomass as a function of
the amount of reserves. (3) Two expressions for Thornton s coefficient
that explain its experimental variability and theoretically underpin
its use in metabolic studies. (4) A mechanism that organisms in
non-steady-state use to rid themselves of internal entropy production:
dilution of entropy production by growth. To demonstrate the
practical applicability of DEB theory to quantify thermodynamic
changes in organisms we use published data on Klebsiella aerogenes
growing aerobically in a continuous culture. We obtain different
values for molar entropies of the reserve and the structure of
Klebsiella aerogenes proving that the reserve density concept of DEB
theory is essential in discussions concerning a the relationship
between organization and entropy and b the mechanism of storing
entropy in new biomass. Additionally, our results suggest that the
entropy of dead biomass is significantly different from the entropy of
living biomass.