ATP 



2C0, 



ADP 



2C.0H 

 y COOH 



2ATP-«>^r 



\ CH, 



2 ADP 



» — '"'^ 



CH,OH 



^'"' 2CH0® 



i 



OOH 



CH.O® 



f- 1 



(9) 2CH0H 



COOH 



CH,0® 

 3CH0H 



2^"^» 2H.0 J'-^OH 

 COO® 



2 ATP 2 ADP 



Fig. 16. A summary of the complex cyclic reactions associated with bio- 

 logical oxidation in which energy-poor ADP (adenosine diphosphate) is con- 

 verted into energy-rich ATP (adenosine triphosphate). These summarize a set 

 of "molecular machines" which provide energy for other biological reactions. 

 (From E. Baldwin, Dynamic Aspects of Biochemistry, 3d. Ed., Cambridge: 

 Cambridge University Press, 1948.) 



to be the main components of the nucleus, the protamines and 

 nucleic acids. These two groups of compounds comprise the chief 

 bulk of the mature nucleus and are believed to constitute the great 

 bulk of the genie material of the cell. 



In most mature cells the most abundant nucleic acids are 

 ribonucleic acid (RNA) and the more complex desoxyribonucleic 

 acid (DNA) (Fig. 17). The basic structure of DNA is composed of 

 alternating pentose sugars and phosphate groups linked together 

 to form an extremely long chain; to each sugar group is linked an 

 organic base. Each chain probably contains a thousand or more 

 sugar groups, yet commonly only four kinds of bases are present in 

 the chain; two of them are larger structures called purines (adenine 



