CONSTITUENTS OF THE BIOSPHERE 25 



(b) Amino Acids Universally Distributed in Organic Materials 



In all living things which have been studied in this connection, one finds 

 the twenty amino acids listed in Table VI. The natural amino acids can 

 be considered as derivatives of L-serine, related to L-glyceraldehyde. 



NH2 OH 



CH2OH— C— COOH CH.OH— C— COH 



H H 



L-serine L-glyceraldehyde 



(c) Amino Acids Occasionally Found 



Besides the twenty amino acids which are universally distributed in the 

 living organism one finds, here and there, certain special amino acids. 

 Among these are the following : 



Hydroxylysine, a, e-diamino-S-hydroxycaproic acid 



NH2 



H2N— CH2— CHOH— CH2— CH2— CH— COOH 



Ornithine, a, S-diamino- valeric acid 



NH2 



H2N— CH2— CHo— CH2— CH— COOH 



^-alanine, /3-amino-propionic acid 



CH2— CH2— COOH 



NH2 



CitruUine, a-amino-carbamidovaleric acid 



NH2 



H2N— C— NH— CH2— CH2— CH2— C— COOH 



y-amino-butyric acid 



H2N—CH2—CH,— CHo— COOH 



and several others : octopine, a-aminobutyric acid, djenkolic acid, ^- 

 thiolvaline, canavanine, etc. 



