THE CHEMICAL PROCESSES IN PLANT RESPIRATION 133 



(I) CeHioOg = 2CH3— CO— COOH + 4H (summarized 



reaction) 



(II) 2CH3— CO^COOH = 2CH3— CHO + 2CO2 



(III) 2CH3— CHO + 4H = 2CH3— CH2OH. 



The very marked reducing property of yeast was taken into 

 consideration in this scheme for the iirst time. Moreover, it 

 is evident from these equations that the formation of CO2 and 

 alcohol represent two separate processes. If part of the acetal- 

 dehyde is not reduced but is worked up in another way it 

 results in an abnormally small yield of alcohol, as is actually 

 the case in the anaerobic respiration of various plants. On the 

 other hand, an excessive formation of alcohol is precluded 

 according to the equations as given and it has never been 

 experimentally found. 



The phases of alcoholic fermentation which precede the 

 formation of pyruvic acid are hypothetically dealt with in the 

 theories of v. Lebedew^ and Neuberg.- According to v. Lebe- 

 dew, the sugar decomposes into glyceric aldehyde and di-hydroxy- 

 acetone. Furthermore, glyceric aldehyde is split according to 

 Kostychev's scheme into one molecule of CO2 and one of ethyl 

 alcohol but di-hydroxy-acetone forms the triose-monophosphate 

 which condenses to hexose phosphate. From the latter the 

 fermentable sugars are reformed, and the whole process is 

 repeated until all the sugar is changed to CO2 and alcohol: 



(I) CH2OH— (CH0H)4— CHO = CHoOH— CHOH— CHO + 



CHoOH— C0~CH20H 



(II) CH2OH— CHOH— CHO = CH3— CO— COOH + 2H 



(III) CH3— CO— COOH = CH3— CHO + CO2 

 (I\) CH3— CHO + 2H = CH3— CH2OH 



(V) CH2OH— CO— CH2OH + RH2PO4 = CH2OH— CO— 



CH2— O— RHPO3 + H2O 



(VI) 2C3H5O2— O— RHPO3 = C6Hio04(0— RHP03)2 



(VII) C6Hio04(0— RHP03)2 + 2H0O = C6H12O6 + 2RHPO4. 



In this theory the biochemical meaning of the formation of 

 hexose phosphate was more nearly explained for the first time. 



1 Lebedew, A. v. Compt. rend. 153: 136. 191 1; Ber. d. chem. Ges. ^5: 3240. 1912. 



2 Neuberg, C. und J. Kerb. Biochem. Z. 53: 406. 1913; 58: 158. 1913- 



