We all know two things about Life on Earth. The first is that almost all Life depends on photosynthesis. However, the efficiency of photosynthesis is surprisingly low – less than 10%. What happens with more than 90% of harvested light energy, which is not used for organic synthesis? It ends up increasing the entropy of the Universe. One visible light photon from Sun is converted by Life into about 20 invisible infrared photons for heating Life's environment. That irreversible process is named entropy production (dissipation). There is no evolution without entropy production. Biological energy transformations (bioenergetics) and biological evolution would be impossible without entropy production as their major result. On the other hand, we know from the Second Law of Thermodynamics that entropy increase caused by thermodynamic evolution ends up in the thermodynamic equilibrium when Life is impossible.
Scientists often have one initial highly motivating goal (for instance, finding a cure for cancer) for devoting countless hours, days, and years to achieve it. My goal was to find the solution for the paradox of biological evolution leading at the same time to ever more complex low entropy structures and an acceleration of the entropy increase (disorder) in the Universe. After publishing about 20 scientific papers on that topic, the time has come to gather new insights into a single book. The book title: Bioenergetics, and subtitle: A Bridge across Life and Universe, does not reveal the unifying concept, which is its focus. Let me explain it. I elaborate in the book how rivers of Life forever change Life and its environment by coupling biological to thermodynamic evolution. The former evolution speeds up the latter. The book explores the usefulness of dissecting the entropy production of enzymes involved in cellular defenses, fermentation, respiration, and photosynthesis, assuming that tightly regulated dissipation is the hallmark of Life. I enclosed in the book an entertaining background about the history of bioenergetics, various attempts to define Life and uncover Life’s origin, and a long chapter about membrane enzymes. Each chapter is a self contained unit with references and a glossary of definitions and explanations.
I found unrealistic aspects of minimal and maximal principles for total entropy production applied to bioenergetics and enzyme kinetics. Neither does justice to strict regulation of overall entropy production level, which is obligatory for the survival of a cell or organism in an often hostile environment. A natural tendency for maximal possible increase of entropy production is allowed by the cell to take its course only in catalytic steps subjugated to biological needs. Thus, we should maximize partial entropy production associated with these biologically productive rate-limiting steps to increase an overall entropy production instead of maximizing total entropy production. Core chapters of my monograph on bioenergetics argue for a tight connection among increased overall entropy production, increased turnover number (catalytic constant), and increased enzyme efficiency after crucial catalytic steps have been optimized for transitional (step-specific) maximal entropy production. That is a natural solution for the question of how nanocurrents produced by enzymes and bioenergetic systems can be optimally channeled toward Life’s preservation and multiplication. After comparing theoretical and experimental results, I show in the book that biological evolution nearly achieved such optimization for enzymes performing the free-energy transduction. For simpler substrate to product converting enzymes, additional catalytic improvements can be achieved, despite biochemical description for some of them as “perfect enzymes.” There are obvious ramifications for the rational design of artificial enzymes as a possible experimental spin-off of these ideas. Theoretical improvements are also possible if our theorem on maximal partial entropy production for a transition between functional states can be generalized by taking into account fluctuations.
You can order the book by D. Juretić from the CRC Press at the link: https://www.routledge.com/Bioenergetics-A-Bridge-across-Life-and-Universe/Juretic/p/book/9780815388388
Davor Juretić was born on October 23, 1944, in Split, Croatia. His main passion in science is understanding the complexity increase of living structures and processes during biological evolution despite high entropy produced and exported to the environment. The conclusion he reached is the following: „Life is the process of channeling partial entropy production into self-maintaining or multiplicative power-producing structures.“
DJ main achievements are:
Discovery of action mechanism and synergy of magainin antimicrobial peptides; prediction method for finding sequence location of membrane buried helices; the proof and applications of maximal transitional entropy production theorem in enzyme kinetics; discovery and design of new peptide antibiotics classes; construction of servers for computational design of antimicrobial peptides. At the University of Split, Faculty of Science, Croatia, Davor Juretić established the Ph.D. program in biophysics with the help of prof. Stjepan Marčelja and other Croatian biophysicists. DJ has expertise in physics, biophysics, bioinformatics, and bioenergetics and close to 100 scientific publications from these fields: http://juretic.medils.hr/.