Living systems entropy

As already mentioned, a continual inflow of energy is necessary to maintain the stationary state of a living system. It is mostly chemical energy which is injected into the system, for example by activated amino acids in protein biosynthesis (see Sect. 5.3) or by nucleoside triphosphates in nucleic acid synthesis. Energy flow is always accompanied by entropy production (dS/dt), which is composed of two contributions ... 

When we speak of mathematical models for biology, we usually refer to formulae (such as the Hardy-Weinberg theorem, or the Lotka-Volterra equations) that effectively describe some features of living systems. In our case, embryonic development is not described by integrals and deconvolutions, and the formulae of the reconstruction algorithms cannot be a direct description of what happens in embryos. There is however another type of mathematical model. The formulae of energy, entropy and information, for example, apply to all natural processes, irrespective of their mechanisms, and at this more general level there could indeed be a link between reconstruction methods and embryonic development. For our purposes, in fact, what really matters are not the formulae per se, but... 

The evolution of living species is concomitant indeed, with obvious ordering of the substance consisted therein. In terms of the classical ther modynamics, this seems like a spontaneous decrease in the entropy of living systems and, obviously, interferes with the Second Law of thermo dynamics. However, this is only an apparent contradiction the entropy increase determines the routes of spontaneous processes in isolated systems but not in open systems that are the living species. In real conditions, the total entropy of the living organisms in their evolution decreases on the condition that... 

Figure 1.1 A simplified diagram of entropy changes in a living system coupled with the formation of products of plant photosynthesis, hv is light quanta initiating the photosynthetic processes with an entropy decrease.

Since entropy (S) is a measure of disorder (randomness), it is the energy that is unavailable for useful work. Entropy values of denatured molecules are high relative to those of native structures (as in protein denaturation). In a living system, entropy is kept at a minimum by utilization of free energy (G) from outside and by increase in entropy of the surroundings. 

Living systems live on negative entropy absorbed from their environment. 

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