Journal of Theoretical Biology 2 c m

ow t p mb ba es chemical reactions, in terms of the chemical equivalent of Carnot’s cycle for heat engines. It is shown that the second law relates the minimal chemical work required to perform a cycle to the Kullback–Leibler divergence produced in its chemical output ensemble from the information gain in computational processes. The first measured as a reduction brought about in the system’s entropy. (kB is Boltzmann’s constant.) ality varies somewhat with taxon, but its total variation is The current paper performs three tasks not undertaken in Paper I: introduction of a particular model of physiological growth through reversible transformations, ARTICLE IN PRESSexplicit definition of chemical work, and derivation of a measure of information appropriate to biochemical orga-nization. The main observation of the paper is tha