Chapter 1 



INTRODUCTION 



About one hundred years ago, after many centuries of eclipse, the molecular 

 theory of the structure of matter became generally accepted as a hypothesis in 

 terms of which the behaviour of the physical world was to be understood. The 

 remarkable development of biology in the past twenty years has now led to the 

 establishment of a universally accepted molecular foundation for biological 

 phenomena also. Testimony to this is the emergence of the area of study known 

 as molecular biology, which is at present the central focus of biological 

 research. 



There are differences between the molecular theories of physics and of 

 biology. For example, the molecular biologist can actually show a sceptic 

 picture of some of his molecules in the form of electron micrographs of proteins 

 or nucleic acids. This could settle a confrontation of the kind which occurred 

 between the renowned physicists Boltzmann and Mach, when the latter said: 

 "You do not kno)v that there are molecules." To this Boltzmann replied: 

 "I know that there are molecules." But Mach ended the argument: "You 

 do not."" However there is a more fundamental form of scepticism which 

 the molecular biologist must be prepared to meet, and that is the question: 

 what is the significance of your molecules ? It is certainly remarkable that in 

 answer it can now be claimed that they carry the information of heredity, 

 that they act as templates for the synthesis of other macromolecules, that they 

 act as catalysts of biochemical reactions, and so on. But this is not enough. 

 Similarly it was not enough that Boltzmann should claim that his molecules 

 were in constant motion and collision as shown for example by Brownian 

 movement. He had to show how the well-established, quantitative relations 

 known as the Gas Laws could be deduced from the properties of his molecules. 

 More generally, he had to show that on the basis of a few assumptions about 

 molecular or "microscopic" behaviour he could derive that set of macroscopic 

 phenomenological laws known as thermodynamics. And essentially he did just 

 this. Assuming that the motion of the molecules was governed by Newtonian 

 mechanics, Boltzmann and others proceeded to construct the kinetic theory of 

 gases and to demonstrate how the gas laws could be derived from kinetic and 

 probabilistic principles. These studies led, in the hands of Willard Gibbs, to 

 the elegant and powerful theory which is known as statistical mechanics, a 

 theory which resolves microscopic and macroscopic structure in physical 

 systems, although in so doing it presented new problems to the theoreticians 

 which have not yet been satisfactorily answered. 



The molecular biologist must do something analogous to this if he is to 

 justify his belief in the fundamental importance of macromolecules and macro- 

 molecular units. From the properties of the "elementary particles" of cells, 



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