Is an Entropy-Based Approach Suitable for an Understanding of the Metabolic Pathways of Fermentation and Respiration?

Abstract

Lactic fermentation and respiration are important metabolic pathways on which life is based. Here, the rate of entropy in a cell associated to fermentation and respiration processes in glucose catabolism of living systems is calculated. This is done for both internal and external heat and matter transport according to a thermodynamic approach based on Prigogine's formalism. It is shown that the rate of entropy associated to irreversible reactions in fermentation processes is higher than the corresponding one in respiration processes. Instead, this behaviour is reversed for diffusion of chemical species and for heat exchanges. The ratio between the rates of entropy associated to the two metabolic pathways has a space and time dependence for diffusion of chemical species and is invariant for heat and irreversible reactions. In both fermentation and respiration processes studied separately, the total entropy rate tends towards a minimum value fulfilling Prigogine's minimum dissipation principle and is in accordance with the second principle of thermodynamics. The applications of these results could be important for cancer detection and therapy.

Entropy Density Acceleration and Minimum Dissipation Principle: Correlation with Heat and Matter Transfer in Glucose Catabolism

“…We have already proved that both RIEDP and REEDP fulfil Prigogine's minimum energy dissipation principle [34,35] that corresponds to the minimum rate of entropy production principle.…”

“…In this section, we derive the general expressions of the entropy density acceleration for glucose catabolism resulting from the rates of entropy density calculated in [34,35] and based on thermodynamic and statistical principles.…”

“…We remind that, in our previous works on the subject [34,35], we have called REEDP the rate of entropy density contributions expressing the entropy flow rate of heat and matter reversibly exchanged from inside the cell to the intercellular environment and due to irreversible processes occurring inside the cell. This results in an increase of the rate of entropy production in the intercellular environment (external to the system represented by the cell) at the expenses of an equal decrease of the rate in the cell.…”

“…In this subsection, we calculate the contributions to the IEDA relevant to glucose catabolism with special regard to lactic acid fermentation and respiration processes. In the calculations, we have taken into account the same assumptions made in our previous studies about the shape of the cells (cubic), the features of the heat and mass flows (unidirectional), the kind of tissue and so on [34,35] based on direct observations for any kinds of cells (normal or cancer). The IEDA ai Q(x,t) due to heat transfer inside the cell is: is the heat thermodynamic force driving Ju with T(x,t) the temperature distribution.…”

“…The latter is fulfilled when thermodynamic systems that are close to equilibrium flow towards the global thermodynamic equilibrium when the rate of entropy density production reaches its minimum value (zero value). This scheme can be applied to any thermodynamic system In our recent works on the subject [34,35], we have studied not only the usual local entropy production defined, in our framework, rate of internal entropy density production (RIEDP) but also the rate of external entropy density production (REEDP) that is related to heat and matter flows from the cell to the environment due to irreversible processes occurring inside cells. Both contributions reduce with increasing time and vanish at global thermodynamic equilibrium.…”