8 UNITY AND DIVERSITY IN BIOCHEMISTRY 



the biosphere contains small amounts of a great number of other elements 

 which are used to good effect. 



Organic chemistry began by the study of certain natural carbon deriva- 

 tives. In the course of its spectacular development during the nineteenth 

 century, it ceased to be a science of naturally occurring compounds and 

 became a science of imaginary molecules in the sense that a molecule not 

 present in nature but synthesized by an organic chemist is a product of his 

 mind and intellect. Nevertheless, a part of organic chemistry forms a 

 whole segment of the natural science of biochemistry- — this is the organic 

 chemistry of naturally occurring substances, a field which depends upon the 

 technical skill of the organic chemist, but whose frontiers and content 

 primarily interest the biochemist. 



This chapter is only a brief outline, and is not a catalogue of the 

 chemical structures present in the biosphere. In our present state of 

 knowledge it would certainly be premature to think of establishing such a 

 catalogue. It is only necessary for an organic chemist to examine minutely 

 the constituents of such a narrow portion of the biosphere as, for example, 

 the musk gland of the musk-deer (see E. Lederer; Animal odours and 

 perfumes, Fortschr. Chem. org. Naturstqffe, 1950, 6, 87-153), toad parotid 

 gland (V. Deulofeu; The chemistry of the constituents of toad venoms, 

 Fortschr. Chem. org. Naturstojfe, 1948, 5, 241-266), the cell of a myco- 

 bacterium (J. Asselineau and E. Lederer; Chimie des lipides bacteriens, 

 Fortschr. Chem. org. Naturstqffe, 1953, 10, 170-273), or the wood of various 

 conifers (H. Erdtman; Chemistry of some heartwood constituents of 

 conifers and their physiological and taxonomic significance. Prog, 

 org. Chem., 1952, 1, 22-63), for him to obtain an imposing harvest 

 of new molecules. Many molecules among them are merely variations on a 

 general theme and their interest is greater still from the point of view of 

 comparisons between living organisms. At the present time, without 

 stating categorically that they are present in all organisms, we can make a 

 list of types of organic structure most widely and generally distributed. 



I. THE THREE PRINCIPAL BIOCHEMICAL STRUCTURES 



A. Aliphatic Acids 



Aliphatic organic acids are very widely distributed in living things, 

 particularly in the form of fats, hence the name "fatty acids". 



The first member of the straight chain saturated series is formic acid 

 O 



H — C corresponding to methane CH4, and the first member 



\ 



OH 



