Quotation: ”The crucial system in biology isn’t a molecule or a molecular class whatsoever, but the interface created by biomolecules in water” [129]
As described, separating electrolytes by a finite-width membrane leads to changes in the distribution of ions, in their macroscopic parameters ’concentration’ and ’potential’. The actual distribution of course depends on the thickness of the membrane and the electrolyte concentration in the segments. Experience shows that although the material of the membrane is a good isolator, the membrane is permeable in some sense (see section 2.8.5), sometimes selectively and sometimes in one direction only; sometimes in a controlled way. The presence of layers on the membrane is experimentally confirmed. It is perfectly seen that the dissociated ions are mainly in the proximal layer of the membrane, see the caption of figure (Fig. 11.22 in [107]). The ionic concentrations are largely different in its two segments and the ion channels have their cap on the side of segment with lower concentration. However, it is experimentally hard to measure anything in this layer; furthermore, the statical interpretation of cellular operation prevents understanding their dynamic operation, including their role in creating and transferring electric signals.
Membranes, and especially the semipermeable ones, are fundamental pieces in many places, from biological objects to industrial filters. They operate on the border of microscopic and macroscopic worlds, combine movements having speeds differing by several orders of magnitude, separate non-living and living matters and combine electrical and thermodynamical interactions. We show that a fragile skin near the surface of biological membranes is responsible for the biological thermoelectric processes.
We might imagine this layer’s importance and operation in line with the Earth’s atmosphere. Its features drastically deviate from the features of the bulks on its two sides. It is separated by a sharp contour on one side and an ill-defined border on the other; its volume is far from being homogeneous. Gravity keeps it in place, and it is at rest. However, sometimes, for some periods, also other (thermodynamical and electrical) forces evoke inside it and lead to transient changes, moving huge masses with high-speeds inside it. Its thickness and mass are negligible compared to those of the bulks on their two sides, and we can describe the bulks without considering their density, mass, size, etc. Still, this thin layer is responsible for the weather; its transient processes define the visibility from both sides (define propagation of electromagnetic fields), and it can protect us from EM radiations. It can temporarily absorb products of slow processes (water evaporation) and deliver masses of high density (much above its density, such as water, sand, etc.) to continental distances, creating the illusion that it stores that matter. Minor changes (natural ones, such as a slight difference in air temperature, and artificial ones, such as injecting condensation nuclei in clouds) can result in enormous changes. Even we can imagine volcanic eruptions as semipermeable gates for material with apparently random operation and distribution of the injected material. Physics sees correctly its importance and role: ”the crucial system in biology isn’t a molecule or a molecular class whatsoever, but the interface created by biomolecules in water” [129], although we add that mainly physical processes and speed gradients control the processes. To describe those complex and continuous phenomena at least approximately, we must separate them into stages. We can describe the stages approximately using omissions, approximations, and abstractions, usually considering only one dominant phenomenon. The described phenomena are interrelated in a very complex way and depend on different parameters. To some point, we can describe that thin layer using a static picture and provide an empirical description of its processes, even though we can give some limited-validity mathematical descriptions for those stages. However, we understand that for describing the time course of the transition (contrasting with step-like stage changes) between those well-defined stages of the atmosphere, we need a dynamic description to discover the laws of motion governing the processes.
Similar is the case with the neuronal membrane and the neuronal operation. Now, we are at the point where their decades-old static description is insufficient. We need to derive the corresponding laws of motion to describe the neuron’s dynamic behavior. We need a meticulous and unusual analysis to derive them. In a neuron, in the abstraction science uses, we put together only an ionic solution, a semipermeable membrane, and currents that reach and leave them. All these belong to non-living matter. As experienced, at some combination of their parameters and gradients, qualitatively different phenomena happen, which, in the abstraction biology uses, are called signs of life; our system starts to belong to living matter. Given that the approximations, the derived abstractions, and the mathematical formalisms describing them are different for the two cases, it looks like we have two different, only loosely bound worlds. We realize we have arrived at the boundary of non-living and living matters, and we must go back to the first principles of science to clarify where their boundary is. However, by using our approach, we may defy that ”the emergence of life cannot be predicted by the laws of physics” [13]. Our artificial duck looks, quacks and swims like a duck.