Keywords: thermodynamic analysis, second-law efficiency, exergy, biochemical compounds, ATP, living cells, intracellular conditions, calculation procedure, glucose degradation, fatty acid degradation, photosynthesis
Thermodynamic analysis of the living cell: design of an exergy-based method
A proper thermodynamic analysis of living-cell processes should elucidate the often-supposed sophistication of biochemical energy and material conversion, and it may provide valuable lessons on the design and operation of future technological processes. The difficulty however is to adequately account for the interaction of biochemical compounds with their complex intracellular environments, especially since available thermodynamic data typically only reflect highly idealised solution properties. To allow more meaningful analyses, this paper describes the various relevant contributions to the exergy of biochemical compounds at specific intracellular conditions. The resulting exergy-calculation procedure is illustrated for the well-known biochemical compound ATP, and it is shown how the potential of ATP to drive processes at intracellular conditions is almost twice the value suggested by biochemical standard Gibbs energy data. The paper discusses the relevance of the more accurate thermodynamic calculations, referring also to the performed exergy analyses of intracellular glucose degradation, fatty-acid degradation, and photosynthesis.