CONSTITUENTS OF THE BIOSPHERE 



S3 



2. Thiamine 



This is the hydrochloride of a molecule formed from a pyrimidine and a 

 thiazole ring. The phosphoric ester of this substance is an important 

 coenzyme. 



CH3 



CH, 



N=C— NH, 

 -C C CH. 



N— CH 



C=C— CH2CH2OH 



\ 



S 



/ 



N=C 



+ H 



CI- 



Thiamine hydrochloride 



(j) Purine Derivatives 

 The purine ring results from the condensation of a pyrimidine ring with 

 another heterocyclic ring, imidazole. 



N =CH 



, 1 s, 



11 3 J' 

 N CH 



HC — NH\ 



HC — N ^ 



Imidazole 



CH 



N=CH 

 I'M H 

 HC: sC — N\ 



N — G — N '^ 



Purine 



Pyrimidine 



Purine forms salts with acids and compounds with bases, it behaves there- 

 fore both as an acid and as a base. 



A number of purines are widely utilized in living organisms. 



/ 



NH, 



O 



// 



N=:C 



HC C- 



H 



-N 



HN— C 



I I H 

 NH,— C C— N 



// 



CH 



N— C— N 



Adenine 

 (6-aminopurine) 



o 



// 



HN— C 



I I H 

 HC C— N 



^ CH 



II II // 



N— C— N // 



Hypoxanthine 

 (6-oxypurine) 



N— C— N 



Guanine 

 (2-amino-6-oxypurine) 



o 



// 



HN— C 



I I H 

 0=C C— N 



CH 



HN— C— N 



Xanthine 

 (2,6 dioxypurine) 



\ 



CH 



