The sources of thermal energy exchange accompanying microbial anabolism

Abstract

Calculations are made of the thermal energy exchanges accompanying the anabolism of Saccharomyces cerevisiae of four substrates using the equations $$ \Delta _{\text{r}} H_{\text{B}}^{{\text{0'}}} = \Delta _{\text{r}} X_{\text{B}}^{{\text{0'}}} + \Delta _{\text{f}} Q_{{\text{ab}}{\text{,B}}}^{{\text{0'}}} $$ and $$ \Delta _{\text{r}} H_{\text{B}}^{{\text{0'}}} = \Delta _{\text{r}} G_{\text{B}}^{{\text{0'}}} + T\Delta _{\text{r}} S_{\text{B}}^{{\text{0'}}} $$ . Contrary to a previous postulate cited in the Discussion, the free-energy changes accompanying anabolism are not zero, but can be either positive or negative. However, their magnitude with either sign is small compared to that of catabolism of the same substrates, so that even with free energy changes that are negative it is unlikely anabolism can be considered a spontaneous process.