CONSTITUENTS OF THE BIOSPHERE 



(/) Acid Aldehydes 



13 



The simplest is glyoxylic acid COOH.CHO, prepared by reduction of 

 oxalic acid COOH.COOH or oxidation of glycol CHaOH.CHgOH. 



Uronic acids are derived from the aldoses by oxidation of the primary 

 alcohol group to a carboxyl group. 



Glucuronic acid is widely distributed in nature, it is the uronic acid 

 derived from glucose. 



H 



c=o 



HCOH 



HOCH 



HCOH 



I 

 HCOH 



I 

 COOH 



D-glucuronic acid 



(g) Keto-acids 



The monoketo acids are differentiated by the symbols a, /3, y, S, etc., 

 according to the position of the ketone group relative to the carboxyl group. 

 They can be prepared by oxidizing the corresponding keto-acids or by 

 hydration of a keto-nitrile. For example, pyruvic acid CH3.CO.COOH is 

 prepared by hydrating CH3.CO.CN. The most important keto-acids in the 

 cell are pyruvic, oxalacetic, a-ketoglutaric and oxalosuccinic, and their 

 decarboxylation is the major source of respiratory carbon dioxide. 



O 



O 



