AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 6 743-R750, Copyright © 1983 by American Physiological Society

ARTICLES

Thermodynamics of living matter: physical foundations of biology

T. H. Benzinger

All major functions of life are exerted by reversible conformational changes of living matter, the genetically coded, giant molecules of proteins, polynucleotides, and biological membranes. Only thermodynamics can answer the questions why these reversible actions occur, why they are inevitable, and what the physical foundations may be on which biology rests. Classical Gibbs-Helmholtz thermodynamics was found to be inapplicable to the interpretation of reactions in living matter, because copious flows of heat without exchange of work obscure the subtle bond-forming or bond-breaking energy transformations that are driving the actions of living matter. An alternative thermodynamic formulation that is universally applicable was developed and applied to numerical examples: formation of a diatomic molecule from the elements, and two conformational changes, a protein folding and the winding of a polynucleotide helix. The subtle energy transformations, bond-forming or bond-breaking, that were causing the two reactions of living matter to proceed in vitro forward or in reverse have been identified as the thermal work function delta Wto(T) and the chemical bond energy delta Ho0. Since the chemical bond energies and the heat capacities delta CoP(T) between reaction temperature and the absolute zero, unchangeable attributes of matter, were the only ingredients used for the treatment, the complexity of the reactions has been reduced--as far as effects and ultimate causes are concerned--to the simplicity of low temperature physics, a solid physical foundation for all biological and medical sciences.