Biochemist

“ It has resulted in the devotion of most of the study which has been given to life processes and living things to animal chemistry, or "physiological chemistry." As a consequence, biochemistry, which deals with the living processes of both plants and animals, is yet in its infancy ”

“ The proteins are the most important group of organic components of plants. They constitute the active material of protoplasm, in which all of the chemical changes which go to make up the vital phenomena take place. Combined with the nucleic acids, they comprise the nucleus of the cell, which is the seat of the power of cell-division and, hence, of the growth of the organism. Germ-cells are composed almost exclusively of protein material. Hence, it is not an over-statement to say that proteins furnish the material in which the vital powers of growth and repair and of reproduction are located. ”

“ On the other hand, the morphologist will urge that green plants derive their peculiar powers of metabolism from the possession of very definite cell-organs, namely chromatophores containing chlorophyll; and will argue that living things without such organs must have preceded in evolution those possessing them. The whole dispute is based on the assumption that plant and animal represent the two fundamental modes of metabolism; whereas the study of the Bacteria shows the possibility of many other modes of life. ”

“ To enable us to say that we know anything about the experimental origination of organisation and life, the investigator ought to be able to take inorganic matters, such as carbonic acid, ammonia, water, and salines, in any sort of inorganic combination, and be able to build them up into protein matter, and then that protein matter ought to begin to live in an organic form. ”

“ So much for the outside sac of the cell—now for the inside. The cell-jelly, or proto-plasm, is made of water, fat, mineral matters, and protein. The water we already know. The fat is made of carbon, hydrogen, and oxygen. The minerals belong to the simple elements.
The protein we know but little about. We are sure that it contains carbon, hydrogen, oxygen, and nitrogen, with a little sulphur or phosphorus, or both, and we know that it is found in all living matter. There is no life without it, so it has been called the "basis of life." ”

“ In the present state of our knowledge concerning the functioning of the proteins, no significance in the physiology of plant life, or metabolism, is to be attached to the particular type of protein material which it contains, at least so far as the simple proteins of the cytoplasm are concerned. ”

“ How vivid the light thrown upon the problems of clinical medicine by the bio-chemists! The story of the fate of protein and purin substances in the animal body, at one time a medley of guesses and gaps, is gradually evolving into one of relative certitude and completeness. Revolutionary, in truth, the change, and many a cherished shibboleth has been ruthlessly cast aside! With admiration not unmingled with awe we see them laying well and truly the foundations upon which in the ultimate scientific medicine must inevitably rest. ”

“ On the one hand we have been able to construct artificially such complex organic molecules as sugar and protein. On the other hand, it has been found possible to produce in siliceous and metallic solutions mimic cells which grow, move, put forth pseudopodia, select their food, propagate by fission, and assume many of the characteristic forms of vegetable and animal life. In more than one laboratory experiments in the generation of life are still being hopefully carried on, and an announcement of their success at any time would not amaze biologists in general. ”

“ The mysteries of organic chemistry are great, and the differences between its processes or reactions as they are carried out in the organism and in the laboratory are many421. The actions, catalytic and other, which go on in the living cell are of extraordinary complexity. But the contention that they are different in kind from what we term ordinary chemical operations, or that in the production of single asymmetric compounds there is actually to be witnessed, as Pasteur maintained, a “prerogative of life,” would seem to be no longer safely tenable. ”

“ But all our experience, hitherto, has proved, that even those cells which are constructed on a simple plan morphologically do, when studied from a purely chemical point of view, show exceedingly complicated relations. Indeed, the study of the processes of metabolism in unicellular forms of life is a study all the more difficult, in comparison with that of more complicated organisms, in that, in the former, it is so difficult to separate the actually absorbed materials from the metabolic by-products, and these again from the secretory or excretory products. ”

“ With the aid of these enzymes, the albuminoid substances are 'peptonized.' In the laboratory such organisms are described as gelatin-liquefying bacteria. A part of the food thus made accessible is appropriated by the microorganisms and in their physiological processes is still further simplified. A part of the carbon is oxidized and escapes into the atmosphere as carbon dioxide, gaseous hydrogen or oxygen is set free, or the two are combined to form water. The nitrogen with which we are here concerned is subject to many changes. ”

“ An exhaustive study of the sources of nitrogen necessary for each separate organism, paying due attention to other nutritious materials and conditions, will no doubt lead to exact methods for the culture of separate cells in the laboratory. Following this line of inquiry we could surround certain microorganisms with peptones whose composition we are familiar with, and so acquire a deeper insight into the processes of their metabolism. ”

“ Everything points to the fact that the cell has agents at its disposal which render it capable of splitting up, into their simplest units, all the complicated substances which are brought to it, or which it itself builds up. In favour of such a view, we may more particularly cite, besides the direct proof of the existence of ferments, the observation that in the metabolism of the cell all the units, out of which the complicated nutritive substances and the components of the cells are built up, are found to occur. ”

“ Since the number of different reactions which take place within a living cell is very great, and since these chemical changes are extremely variable in type, it follows that the number of different enzymes which must exist in either a plant or an animal organism is likewise very large. For example, fourteen different enzymes have been isolated from the digestive system, and at least sixteen from the liver, of animals. They are universally present in living protoplasm of every kind, from the most minute bacterium to the largest forest trees, in the plant kingdom ”

“ As to the metabolism within the cell, no more is known than is the case with other cells, nor even as much. The materials used for growth and as sources of energy are taken into the cell, built up into various compounds some of which have been enumerated and in part broken down again. Carbon dioxide and water are formed in the latter process. ”

“ Where the analytical powers of the microscope in anatomy can go no farther, chemical analysis of the composition of the cell steps in. By its means the discovery is made that there is no elementary difference between organic and inorganic nature, for only such chemical elements as are known to exist in the inorganic world are found in the organic. On the other hand, however, the living cell-substance possesses chemical compounds which find analogues nowhere in inorganic nature. The characteristic organic substances which are present in every cell are proteids and proteid-compounds. ”

“ He simplifies the catalytic theory of the enzyma by tracing all the phenomena of life to the catalytic metabolism of one single chemical compound, the plasm, and regards its active molecules, the biogens, as the ultimate chemical factors of the vital process. While the enzyma hypothesis assumes that there are in each cell a great number of different enzyma which are all co-ordinated, and each of which only performs its little special work, the biogen hypothesis deduces all the vital phenomena from one compound, the biogenetic plasm ”

“ Enzymes are found in all parts of the animal organism and those which are active in the digestion of food, the metabolism of digested material, the coagulation of blood, etc., have been extensively studied. A discussion of these animal enzymes would be out of place in such a text as this, however, and the following list includes only enzymes which are known to occur in plant tissues. ”

“ If the organic compounds produced by plants be classified with reference to their uses in metabolism into the three groups known, respectively, as temporary foods, storage products, and permanent structures, it is clear that the carbohydrates which have been discussed in this chapter may fall into either one of the first two of these classes. There can be no doubt that the first products of photosynthesis, whichever ones they may be in different plants, may be directly used as temporary foods, to furnish the energy and material for the building up of permanent structures. ”

“ I am afraid that your other suggestions are not germane to the problem of nucleic acid synthesis and metabolism, a problem that has been occupying all my time. In fact, I’ve been doing with three to four hours of sleep these days. With the kind of concentration that I can offer the problem, there is no question that the data are falling into line, and our research is going rather well. We will show, I hope, fairly conclusively that there is little or no interconversion between the two types of nucleic acid synthesis in the cell. ”

“ The chemistry of the living cells—their anabolism, or how fresh material is built into their structure; their katabolism, or how the same structure is broken down that work may be done; in fact, the general metabolism—is so complicated, and so little understood as yet, and requires so extensive a knowledge of chemistry to follow, that it is best left alone by people who do not want to go into it deeply. ”

“ Our progress in the field of the chemistry of the different kinds of cell units, and of their nutritive bases, has brought us nearer to this objective, but a large part of the road lies before us yet, before we shall obtain such an exact knowledge of the composition of certain albuminous substances, such as phosphatides and nucleoproteids, &c., as to be able to properly appreciate differences of configuration, as well as differences of structure. ”

“ Though we do not yet know the precise nature of the ferments, yet their specific activities, and their great importance in regard to cell metabolism and cell structure, are well known.
Without energy no cell can do work or produce heat, and it is in energic metabolism that we find a true picture of the functions of the cell. How the cell procures the required energy, in what manner it makes use of it, and so on, we can learn only by an accurate and possibly exhaustive study of the finer metabolic processes that go on in the cell. ”

“ We conceive that, in the primordial world, as now in the laboratory, higher types of organic substance were formed at the expense of lower types, and that gradually, after repeated reactions and under favorable conditions, they resulted in organizable protoplasm, a substance which is very susceptible of modification. Protein, as we know, may exist in upward of one thousand isomeric forms, and, by combination with itself and with other substances, it yields products still more complex, and in countless numbers. ”

“ The chemical materialist conceives certain compounds, never well-known ones mark you, enzymes for example, to be thus supremely endowed. The biological materialist on the other hand, ascribes this exalted role to imaginary, invisible living bodies hidden deep within the germ and other cells. Biology of the last three decades has bestowed mighty powers upon such bodies under the designation "determinants." Only those familiar with the technical literature of the science during this time can have any notion of the influence these bodies have had. ”

“ Protoplasm consists, to the extent of about 60% of its total mass, of a mixture of various nucleo-proteids—that is to say, of those substances which, in molecular structure and chemical composition, are the most complex bodies known. In association with them are always found varying amounts of fats, carbohydrates, and other bodies, and such compounds are always present in the living substance to a greater or less degree as products of both upward and downward metabolism. ”

“ We come next to the agency of chief importance among those that work changes in organic matter; namely, chemical affinity. How readily vegetal and animal substances are modified by other substances put in contact with them, we see daily illustrated. Besides the many compounds which cause the death of an organism into which they are put, we have the much greater number of compounds which work those milder effects termed medicinal—effects implying, like the others, molecular re-arrangements. ”

“ Of these, carbon and oxygen unite, in certain proportions and under certain conditions, to give rise to carbonic acid; hydrogen and oxygen produce water; nitrogen and hydrogen give rise to ammonia. These new compounds, like the elementary bodies of which they are composed, are lifeless. But when they are brought together under certain conditions they give rise to the still more complex body, protoplasm, and this protoplasm exhibits the phenomena of life.’
Until we have further knowledge of the changes which constitute these phenomena, physiology must remain descriptive rather than explanatory. ”