Molecular Biology and TeleologyMolecular biology is the study of the molecules that carry out all of the processes that collectively sustain life in the individual organism, and transmit it across the generations. It might be said to consist of three broad classes of phenomena: structural, biochemical, and functional.
The structural phenomena of molecular biology are the material entities of which living cells are constructed, including small molecules (water, sodium ions, etc.), medium-sized molecules (ATP, NADH, etc.), macromolecules (proteins, polynucleotides, polysaccharides), and organelles consisting of complexes of macromolecules (ribosomes, mitochondria, chromatin, etc.). By now, these entities have all mostly been identified, classified into families, and their chemical compositions and structural principles for the most part elucidated.
The biochemical phenomena of molecular biology are the physical interactions that the first class of phenomena are involved in. Whenever any two molecules interact with each other, various chemical bonds are created and/or broken. In addition, individual reactions take place within larger, often highly complex cycles of reactions, such that the products of one step in the cycle become the reactants in the next step, until the cycle is completed and the molecular species assume their original equilibrium proportions. The citric acid cycle, an essential step in metabolism in almost all organisms, is perhaps the best-known example of such a process, but there are countless others. The field of bioenergetics studies the way in which all the various metabolic processes are interconnected in overall energy budgets. In all of these cases, quantum mechanical, thermodynamic, and other physical principles suffice to explain the individual biochemical interactions.
The third class of phenomena studied by molecular biology is where the controversy lies. Somehow, it does not seem enough merely to understand the chemical composition of the various entities (say, that proteins are polymers made of amino-acid units) and the physical principles underlying the various individual interactions (say, the way that the active site of an enzyme bonds with its substrate). Something more seems to require explanation: namely, the fact that there is a kind of regularity or order governing the way in which all these entities and interactions work together in order to accomplish specific tasks and to satisfy specific needs of the cell as a whole. This purposive order is what is meant by functional organization. For example, even after we have analyzed the structural constitution of an enzyme or enzyme complex (say, ATP synthase) and explained its biochemical interaction with its substrate (ADP), we still have not fully explained what has happened until we have noted the purpose that this interaction serves in the overall functional organization of the cell: in this case, ATP synthesis. So, the question is: Are such functional phenomena, which are indisputably a part of molecular biology, also completely explained by contemporary chemistry and physics?
Almost everyone agrees that the answer to this question is no. That is, physics and chemistry, in and of themselves, do not give a fully adequate explanation of functional phenomena. Thus, while molecular biology may explain how all the parts of a cell work individually, it cannot by itself explain the fact that the parts are functionally organized to work together in the way that they do. To account for this complex, goal-directed organization---which is deeply mysterious from a physical point of view---we are told that a different kind of explanation altogether is required. This explanation is the theory of natural selection.
Editor(s): James Barham
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