A comparison of energy changes accompanying growth processes by Saccharomyces cerevisiae

ISSN： 1388-6150

Source： Journal of Thermal Analysis and Calorimetry, Vol.104, Iss.1, 2011-04, pp. : 193-200

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Abstract

Calculations are made using the equations ∆_r G = ∆_r H − T∆_r S and ∆_r X = ∆_r H − ∆_r Q where ∆_r X represents the free energy change when the exchange of absorbed thermal energy with the environment is represented by ∆_r Q. The symbol Q has traditionally represented absorbed heat. However, here it is used specifically to represent the enthalpy listed in tabulations of thermodynamic properties as (H _T − H ₀) at T = 298.15 K, the reason being that for a given substance TS equals 2.0 Q for solid substances, with the difference being greater for liquids, and especially gases. Since ∆_r H can be measured, and is tangibly the same no matter what thermodynamics are used to describe a reaction equation, a change in the absorbed heat of a biochemical growth process system as represented by either ∆_r Q or T∆_r S would be expected to result in a different calculated value for the free energy change. Calculations of changes in thermodynamic properties are made which accompany anabolism; the formation of anabolic, organic by-products; catabolism; metabolism; and their respective non-conservative reactions; for the growth of Saccharomyces cerevisiae using four growth process systems. The result is that there is only about a 1% difference in the average quantity of free energy conserved during growth using either Eq. 1 or 2. This is because although values of T∆_r S and ∆_r Q can be markedly different when compared to one another, these differences are small when compared to the value for ∆_r G or ∆_r X.