RESPIRATION 



473 



The main difference between this system and that of 

 Lipmann is that the high-energy bond is formed before the 

 inchision of the phosphate. This considerably enlarges our 

 ideas concerning the mobilisation of energy in the respiratory 

 process. 



succinate 



S.D. 



aKg 



p-OH 



(DPT) 



(CoA) 



cyt. 6 



(dehydrogenase) 



(factor) 



L.A. 



I 

 DPN ^ 



I 



\ (factor) 

 ^ cyt. c 



i 

 cyt. a 



cyt. 03 



\ 



Scheme A 



(aKg'= a-ketoglutarate ; CoA = coenzyme A ; DPN =diphos- 

 phopyridine nucleotide; fp= flavoprotein ; cyt. =cytochrome ; 

 S. D. = succinic dehydrogenase ; L. A. = a-Hpoic acid ; P-OH 

 = p-hydroxybutyrate ; DPT = diphosphothiamiue) 



Fig. 44. Diagram of the oxidative transformation of 

 respiratory substrates (after Slater). 



Slater has worked out the above scheme (Fig. 44) of the 

 links of the chain of oxidation of a-oxoglutarate, succinate 

 and /3-hydroxybutyrate in which he remarks on the possible 

 ways in which phosphorylation may take part. According 

 to this scheme phosphorylation takes place at the following 

 stages of the process: between reduced diphosphopyridine 

 nucleotide (dpnh) and cytochrome c (here there may be two 

 stages at which phosphorylation occurs) ; between succinate 

 and cytochrome c ; and between cytochrome c and oxygen. 



The great variety of the sequences of reactions in the 

 oxidative chain in different members of the animal and 

 vegetable kingdoms itself indicates the relatively recent origin 

 of the system under discussion, suggesting that evolution 



