Thermodynamics of Biological Growth

ACCORDING to some recent opinions, living organisms are nearer to open systems in the thermodynamic sense than to classical closed systems, although an organism plus its environment constitute a system which must be regarded as closed. While closed systems eventually reach equilibria characterized by minimum Gibbs free energy and maximum entropy, Prigogine 1 and de Groot 2 have predicted that open systems will approach steady states of minimum entropy production. On this basis, Prigogine and Wiame 3 have inferred that living organisms grow towards a state of minimum metabolism per unit mass, but this view and other discussions 4 on this theme are subject to two criticisms. On one hand, the theorem of minimum entropy production holds only for open systems very near to the steady state 5 and, on the other, it has never been tested experimentally for living organisms so that conclusions derived from it are weakened to some extent.