64 UNITY AND DIVERSITY IN BIOCHEMISTRY 



It is very stable in alkaline solution, but not in acid solution. A large 

 number of important biochemical structures are derived from pyrophos- 

 phate, similarly triphosphoric acid also plays an important role in bio- 

 chemical energetics in the form of its derivatives, adenosinetriphosphate 

 (ATP) and uridinetriphosphate (UTP). 



(b) Phosphoric Esters of Glycerol and Glyceric Acid 



The monophosphoric ester of glycerol, or glycero-phosphoric acid, 

 exists in the two isomeric forms a and ^ : 



CHoOH CHoOH 



I I 



CHOH CH— O— PO3H2 



I I 



CH2— O— PO3H2 CHoOH 



P 



Glycerophosphoric acids 



and corresponding to these are the monophosphoric esters of glyceric acid, 

 a and ^ phosphoglyceric acids, 



CO2H CO2H 



1 1 



CHOH CH-O-PO3H2 



I I 



CHo— O— PO3H2 CHoOH 



3 or j8 2 or a 



Closely related to the above acids is phosphorylated pyruvic acid 

 (phosphoenolpyruvic acid) : 



CO2H 



I 

 C— O— PO3H2 



II 

 CH2 



(c) Triosephosphates 



Phosphodihydroxyacetone CH2OH-CO-CH2O-PO3H2 is a triose ester 

 a triosephosphate. Another member of the same class is its isomeric 

 aldehyde, phosphoglyceraldehyde or 3-glyceraldehyde-phosphoric acid : 



CHO— CHOH— CHo— O— P0(0H)2 



These two triosephosphates, unlike the hexose phosphates, are easily 

 hydrolysed by alkali. 



