Hans Barstrbm 



259 



vessels, which is a reaction at the /-level, an anaerobic reaction. This 

 is inhibited by such agencies as iodoacetate and fluoride, known to 

 attack the dehydrogenase systems or the anaerobic process of glycolysis. 

 If it is true that the cytochrome system may be occupied by organic 

 acids, it follows as a consequence that the salt respiration system might 

 work with the organic acids present in the cell and not only when 

 mineral salts are added externally. That is just what Lundegardh has 

 assumed to occur, and it is supported by other indications in the same 



O-LEVEL 

 MEDIUM 



02 





© 



CYTOPLASM 



I- LEVEL 



VACUOLE 



^RESPIRATION 

 *■ oxiDAT/OH SYS T E M 



© 



A CYTOCHROMES 



DEHYDRO- 

 1 Cif/V/*770/V 



H 



acid cycu\ 



Fe 



Fe 



ORGANIC ACIDS 



Fe y 



■« (e 



t 

 PFI 



(A) (org.-A) 



»(A)>»--- (ORG.-A) ^HZE (ORG.-A^ v(g ^ (ORG-A-) >» 



Figure i. Scheme for the active absorption of ions. The salt respira- 

 tion system is oriented transversely across the cytoplasm. At the inner, 

 dehydrogenation level, protons and electrons are produced, and they are 

 moved to the outer, oxidation level in exchange for salt cations and anions, 

 respectively. Solid arrows denote only chemical reactions or equilibria; 

 broken arrows, mechanical transport. 



direction. For instance, Robertson has shown that a respiration sensi- 

 tive to hydrocyanic acid also occurs in the absence of mineral salts 

 under certain conditions. Inhibition by hydrocyanic acid may cut off 

 not only the whole additional salt respiration but a part of the apparent 

 ground respiration as well. These and other observations show that the 

 cytochrome-regulated respiration is not exclusively dependent on the 

 addition of salt. It is apparently only a question of relative rates of res- 

 piration with and without mineral salts. Salts, presumably anions, 

 greatly activate a respiratory system, and it may be assumed that this 

 activation involves the exchange of the organic acids for the mineral 



