BIOCHEMISTRY. — Biochemistry is that branch of physiology which studies the chemical composition and the physicochemical properties of animal or plant organisms in order to interpret subsequently the dynamism of the chemical and physicochemical processes that occur within them. The ultimate and essential aim of biochemistry is to establish the relationships between these processes and the manifold manifestations (functions) of life. Depending on whether the subject is a healthy or a diseased organism, we have normal or pathological biochemistry.
The earliest beginnings of biochemistry date back to Paracelsus (1493–1541) and to the iatrochemists of the 17th century; but only in the last sixty years, after the impetus given by Justus V. Liebig (1850), has it developed at a dizzying pace and acquired the form and substance of a science in its own right. The progress of biochemistry, besides being connected with advances made in this last century by chemistry and physics, is also to be attributed to the ingenious creation of a multifaceted and original methodology, suited to the needs of the new science that was emerging and which increasingly captivates scholars by its fertile prospects. It is beyond dispute that today biochemistry represents the portentous ferment that, permeating all biological sciences and medicine in particular, has in a short time succeeded in channeling research toward a new direction, added to the old morphological one, which, despite its glorious past, now appears largely exhausted. Among the most recent achievements of biochemistry we may recall vitamins, hormones, the identification of ever-new enzymes and their chemical constitution, intracellular oxidation-reduction phenomena, the interpretation of immunological phenomena, and the discovery of gamones, organizers, etc.
To arrive at an objective evaluation of
the position of biochemistry in the field of biological sciences, it should be borne in mind that the only form of energy available to animals is chemical energy, which they take in from the external world through food. On the other hand, every manifestation of life can be considered, in a broad sense, as an energetic expression; and since the law of the conservation of energy admits no exceptions, it follows that even the manifestations of life must be interpreted as the result of transformations of the original chemical energy into other forms of energy (mechanical, osmotic, surface, etc.). Thus, for example, the function of muscles essentially consists in the transformation of the chemical energy of the fundamental muscle metabolite, glycogen, into mechanical energy.
Plant organisms, unlike animal ones, besides chemical energy derived from the energetic substances they can assimilate, also have solar radiant energy at their disposal; but this latter, once captured by the plant, is transformed, by virtue of chlorophyll action, into chemical energy through the synthesis of organic substances rich in this form of energy. It follows that even for plants, as for animals, the initial energy from whose exploitation the various functions derive is always chemical energy.
This simple observation alone would suffice to place biochemistry at the foundation of any branch of biology (v.). It indeed directly addresses the physicochemical determinism of biological functions and seeks to reveal and order the constituent links in the complex chains of phenomena that occur between a given function and the chemical energy that is the primary and necessary cause of that function, through metabolic processes. Since biochemistry has succeeded in deciphering and understanding the biochemical processes underlying many phenomena of life and since its recent discoveries give well-founded hope that such knowledge will extend to all such phenomena, the conviction may arise that through the continuous progress of biochemistry, the ancient and persistent human tendency to explain life through a simple and exclusive physicochemical mechanism will soon or late be satisfied. This conviction, however, is the result of a superficial impression formed at first glance; to those who delve more deeply into the study of biochemistry, it soon becomes clear that the increasingly sensational progress of this science inevitably leads to the demonstration that above the physicochemical phenomena occurring in living beings, there exists a fact that dominates and surpasses them; and this fact is precisely the astonishing coordination by which such phenomena are directed toward a finality that only blind prejudice can attempt to deny or ignore. Whichever vital manifestation we undertake to investigate in terms of its physicochemical determinism, we will always arrive at the conclusion that the physicochemical processes, which represent the material and energetic substratum of that vital manifestation, in their enormous complexity and infinite modalities of development, are in every case coordinated in time and space in such a perfect and adequate manner that their outcome is evidently directed toward the satisfaction of some purpose, which coincides with some function of the organism. But at the very moment when a function arises from this complexity of chemical and physical processes, which surpasses all imagination and is always coordinated, the transition from the material to the immaterial has already occurred, because in the function, precisely as such, we are compelled, willingly or unwillingly, to recognize some finality of a more or less elevated order; and between this finality and the individual chemical and physical processes that preceded the function to which the finality itself refers, we find no causal link, but only a relationship of simple determinism, inasmuch as those processes remain inexorably blind and fatal, as is characteristic of any physicochemical process.
What thus distinguishes life and which biochemistry makes all the more evident the more it progresses, is not the infinite possibility of physicochemical phenomena inherent in tissues and organisms—a possibility surpassing all human inventiveness and technical ingenuity, realized or realizable—but the precise order in which such phenomena occur, a condition that is in turn prerequisite for the marvelous unfolding of these phenomena to give rise to those even more wonderful events, imbued with a transcendent character, represented by the functions of individual organs with their inescapable finalities.
It goes without saying that what we have said applies not only to any function but in a particular way to introspective functions, in all their range, from simple sensation to the divining intuition of genius. We may admit, and we do not deny, that one day, for example, we may succeed in constructing a muscle fiber and unveil all the chemical and physical events that condition a contraction; but from these events that render possible those material muscle contractions which determine the hero’s impetus and propel him to his supreme sacrifice, we could never ascend to the sublimity of his ideal.
In defining biology and its tasks, we have taken care to warn how the hope of explaining life through a simple chemical and physical mechanism goes beyond the very possibilities of biology itself, despite the dazzling victories of this science. For at the apex of such a mechanism, undeniable in living beings, we always encounter phenomena of a transcendent nature, which are precisely those that characterize life itself. But if biology is not the omnipotent goddess that removes or will remove the veil of the mystery of life, it remains true that this new and fervent branch of science offers the scholar a field of investigation that shows no signs of having limits, and into which one may venture with the boldness and enthusiasm of a pioneer setting out to explore a vast and still unknown region. It must not, however, be thought that the virginity of this terrain makes the progress of biology easy and straightforward; indeed, the difficulties it encounters are certainly greater than those opposing the progress of chemistry and physics, with which biology shares its methodology.
These difficulties are, first of all, inherent in the very complexity of biological systems, even if we wish to reduce them to the level of simple physico-chemical systems. Such systems, whether represented by whole organisms or their parts, are all colloidal systems, and as such the course of the biochemical processes that take place within them is influenced by the immense number of interfacial surfaces present and constituting an independent variable, which usually does not appear in the processes studied by pure chemistry and physics and which complicates them immeasurably. The biocolloids (v. COLLOIDI), on the other hand, are colloids in