CHAPTER 1 



Keratin and Molecular Biology 



Macromolecules and biology 



Biological processes, whatever the organism, plant or animal, are 

 inseparably associated with macromolecules. Some of these form the 

 solid frameworks which support and protect organisms; others as more- 

 mobile particles effect the reactions with each other and with smaller 

 molecules which we recognize as ultimately characteristic of life; others 

 again form the material basis of inheritance. It is no more than the truth 

 to say that the way of life of an organism is determined by the nature of 

 the large molecules synthesized by its cells. The familiar difference 

 between the higher plants and animals furnishes an example as illustration. 

 Animals are able to move about or to move their parts because certain 

 of their cells have the ability to synthesize contractile muscle proteins. 

 Plant cells have largely lost this power; on the other hand they are 

 able to form and secrete quantities of rigid encrusting substances, 

 such as cellulose, which permit of a very different anatomy and mode 

 of life. 



This statement is indeed equivalent to saying that animals have muscles 

 and plants have woody cell walls; but the emphasis is different. In 

 drawing attention in the first place to the macromolecular content of the 

 cell and the organism as the basic factor determining behaviour, we 

 are led to ask a particular kind of question, of which the following are 

 examples : 



(a) What are these macromolecules and what is their molecular 

 structure ? 



(b) Can we predict their biological function from their structure ? 



(c) How are these molecules synthesized and what factors control their 

 synthesis ? 



(d) When do they appear in the course of embryonic development 

 (molecular ontogeny) and how do they influence this development ? 



(e) How and when were the various molecular types evolved (molecular 

 phylogeny) and how has their appearance influenced the course of 

 evolution ? 



Attempts to answer these questions are already engaging much attention 

 and undoubtedly theoretical biology of the future will base itself largely 



