D 



Molecular Biology 



Introduction to Part D 



In theory, all of biology could be explained in terms of 

 molecular phenomena. Such descriptions appeal to the 

 biophysicists as being in some way more fundamental; 

 they involve the properties of far simpler systems than 

 whole organisms. In this text, the earlier sections dealt 

 with properties of cells and groups of cells. In Part D, 

 the molecular mechanisms are discussed. 



Chapter 1 5 describes the molecular form of two impor- 

 tant classes of biological molecules, the proteins and the 

 nucleic acids. In Chapter 16, the interaction of these 

 molecules and ionizing radiations are considered. The 

 basic similarities between synthetic high polymers and 

 proteins and nucleic acids are emphasized. 



One very important function of proteins is to control 

 the rate of biological reactions. Proteins which are 

 responsible for such catalytic action are called enzymes. 

 Chapters 17 and 18 present mathematical analyses of the 

 kinetics of enzyme catalyzed reactions. 



Certain molecules owe their biological significance to 

 their reactions with light. The roles of these photo- 

 sensitive molecules in vision and in photosynthesis are 

 described in the last two chapters of Part D. 



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