Nano-protoplasm: the ultimate unit of life.

Among the most promising scientific achievements of the 19th century was the recognition that the laws governing the dead world also govern the world of the living and that life has a physical basis called protoplasm. Regrettably, the definition of protoplasm provided then was (inescapably) incorrect, offering a (legitimate) reason for rejecting the concept of protoplasm by an overwhelming majority of later investigators, teachers and other opinion-makers. Without a recognized physical basis, Life itself also faded into the limbo of the unexplainable. However, eventually the needed relevant parts of physics and chemistry to give a more cogent definition of protoplasm became available. That then made possible the construction in the early 1960's of a unifying theory of the living cell, named the association-induction (AI) hypothesis. Historically speaking, the AI Hypothesis is the heir to the general concept of protoplasm as the physical basis of life-incorrect as the initial definition of protoplasm was notwithstanding. In the AI Hypothesis (AIH) the true or ultimate physical basis of life is not what the advocates of the protoplasm once considered as the physical basis of life. What they saw and construed as the physical basis of life is a particular kind of macroscopic protoplasm. In the AI Hypothesis, the basic unit (or physical basis) of life is microscopic protoplasm or nano-protoplasm, of which all macroscopic protoplasm is made. The AI Hypothesis also had no difficulty offering a new definition to what life is in terms of fundamental physical-chemical laws. Nano-protoplasm is defined by what it is and what it does. In greater detail, it is defined (i) by its chemical composition given in Equation 1 on p. 124; (ii) by the mutual spatial and energetic relationships among the components as illustrated diagrammatically in Figure 5 on p. 125; and (iii) by the ability of these components to exist as coherent assemblies in either one of two alternative states, the resting and active living (or dead) state as according to Equation 5 on p. 142. The review then describes the AIH-based electronic and molecular mechanisms for the coherent assemblage of the components, for the maintenance of the living states and for the auto-cooperative transitions between the resting and active (or dead) living state. Having completed the theoretical section, the review goes on to describe the experimental testing of the theory carried out in the past forty-some years (and even in time before that by authors who knew nothing of the theory.) These experimental studies fall into two broad categories. In the first category, are the experiments performed on ultra-simple models of nano-protoplasm made up from pure chemicals as prescribed in Equation 1 on p. 124. The results show that they indeed behave qualitatively like that illustrated in Figure 5 and quantitatively follow the dictates of Equation 5. In the second category of experimental testing, parallel studies were carried out on nano-protoplasm as part of living cells--in carrying out each one of the four classical functions of cell physiology: (1) solute and water distribution; (2) solute and water permeability; (3) cellular resting and action potentials; (4) cellular swelling and shrinkage. The results show that the nano-protoplasm in situ too qualitatively behave like that shown in Figure 5 and quantitatively follow the dictates of Equation 5. The review ends on a discussion section, examining how cogent do the experimental data accumulated thus far support to the AI version of the concept of nano-protoplasm as the most basic unit of life.