Abstract: MATH/CHEM/COMP 2002, Dubrovnik,
June 2429, 2002

Farfromequilibrium
biochemical circuits
Davor Juretic Department of Physics, Faculty
of Natural Sciences, Mathematics and Education, University of Split, N. Tesle
12, HR21000 Split, Croatia Predicting behaviour of very complex networks of biochemical reactions is the next important goal after the completion of different genome projects. The consensus seem to be that some optimization principle based on any one (or several) of many proposed biological objective functions would help in reaching that goal. From the physical point of view life is very efficient entropy producer. Rather than looking for the optimization principle(s) from biology, we shall examine extremum principles for the entropy production, with a goal to find if any of them is able to predict strong observed fluxes in biochemical circuits that are important in cellular bioenergetics. There are several possible approaches how to apply nonequilibrium thermodynamics to steady state biochemical circuits^{1,2}, and in particular to photosynthesis^{3,4}. Each of them is connected with some difficulties that will be discussed. We shall use our own method for calculating the entropy production and efficiency of several simple kinetic models for photon driven and ATP driven biochemical circuits operating in a farfromequilibrium steady state. In particular, we shall show that maximal entropy production implies the optimization of the available power when the system works far from equilibrium, which is in accord with biological objectives. ^{1 }D. A. Beard, S.D. Liang, H.
Qian, Energy Balance Analysis of Complex Metabolic Networks, Biophys. J.
(2002), to be published. ^{2} T. L. Hill, Free
Energy Transduction and Biochemical Cycle Kinetics, SprigerVerlag, 1995,
New York. ^{3} G. Meszena, H. W. Westerhoff,
Nonequilibrium Thermodynamics of Light Absorption, J. Phys. A: Math. Gen.
32 (1999) 301311. ^{4} C. D. Andriesse, M. J.
Hollestelle, Minimum Entropy Production in Photosynthesis, Biophys. Chem.
90 (2001) 249253. 