REACTIONS OF CARBON DIOXIDE 



87 



Structural formulae of some coenzymes 



Formula 



Abbrevia- 

 tion 



N=C— NH3 



I I 

 H— C C— N 



i C— H 



— O 



OH OH 



OH OH 



N— C— N C— C— C— C— CH,— O- 



I I I 



-P- 



H H H H O 



Adenosine triphosphate 



-0— P— O- 



6 



OH 



I 

 -P— OH 



O 



Adenosine diphosphate 

 (ATP minus one phosphate group) 



H 



NH, 



HC C— C=-0 



'I I 



HC C— H 



\ // 



N+ 



H— C— 



I 

 H— C— OH 



1 

 H— C— OH 



I 

 H— C— 



N=C— NHa 



I I 

 H— C C— N 



C 



/ 



N— C— N 



I 

 H— C 



I 

 H— C— OH 



O 



H— C- 



OH 



I I 



-O— P— O— P 



H— C— OH 

 H I 



O H— C — 



O 



-O— C— H 



I II ' 11 I 



H O O H 



Diphosphopyridine nucleotide 



(Coenzyme I) 



Triphosphopyridine nucleotide 

 (Coenzyme II) 



FIG. 6.1 



ATP 



ADP 



DPN+ 



(oxidized) 



DPNH 



(reduced) 



TPN+ 

 TPNH 



Carbon dioxide as a cellular metabolite 



In the fermentation of sugar, when ethanol is formed, 

 carbon dioxide is Hb,erated and the cell would appear to 

 have no further *use' for it. On the other hand it had long 



