8 PHYSIOLOGY OF NUTRITION 



It is seen that both contain magnesium, the content of this element being about 

 5.6 per cent., by weight. Iron is apparently necessary for the formation of 

 chlorophyll in plants, but it is not a part of the pigment. Iron does occur, 

 however, in the molecule of hemoglobin, which is somewhat closely related to 

 chlorophyll, chemically. An explanation 6 of this is to be found in the fact that 

 the actions of these two substances in the cell are directly opposed; for the 

 analytic action of hemoglobin, iron is essential, while magnesium seems to 

 take part in the synthetic processes effected by chlorophyll. 1 



Almost a third of the chlorophyll molecule is composed fo phytyl, the radical 

 of phytol, 2 an unsaturated mono-hydric primary alcohol of the aliphatic series, 

 having the composition C 2 oH 40 and the probable structure shown by the 

 following diagram: 



CH 3 — CH— CH— CH— CH— CH— CH— C = C CH— CH 2 OH 



CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 



Phytol is readily oxidized in the presence of air. Willstatter suggests that it 

 may be obtained from isoprene in the following way: 



4C 5 H 8 (isoprene) + H 2 + 3H2 = C 2 oH 4 oO(phytol). 



Carotin appears also to be related to isoprene. The phytyl of chlorophyll 

 may be replaced by the ethyl group if the leaves are treated with ethyl alcohol. 

 This replacement is effected by an enzyme known as chlorophyllase. 3 



Another alcohol radical is present in both the chlorophylls, namely, methyl 

 (CH 3 ). They thus appear to be esters of a complex, dicarboxylic acid, one of 

 the two carboxyls (COOH) being joined to phytyl and the other to methyl. 



Regarding the complex acids that form the basis of the chlorophylls, there 

 still remain some uncertainties, but it appears to be related to a tricarboxylic 

 acid that may be represented by the formula (C 3 iH 29 N 4 Mg) (COOH) 3 , but one 

 of the carboxyls is inactive, so that a dicarboxylic acid results. A general idea 



1 Willstatter, Richard, Zur Kenntniss der Zusammensetzung des Chlorophylls. Liebig's Ann. Chem. u. 

 Pharm. 350: 48-82. 1906. Willstatter, Richard, and Benz, Max, Ueber krystallisirtes Cholorphyll. 

 Ibid. 358: 267-287. 1908. 



2 Willstatter, Richard, and Hocheder, Ferdinand, Ueber die Einwirkung von Sauren und Alkalien auf 

 Chlorophyll. Liebig's Ann. Chem. u. Pharm. 354: 205-258. 1907. Willstatter, Richard, Mayer, Erwin 

 W., and Huni, Ernst, Ueber Phytol. I. Ibid. 378 : 73-152. 191 1. 



3 Willstatter, Richard, and Stoll, Arthur, Ueber Chlorophyllase. Liebig's Ann. Chem. u. Pharm. 378: 

 18-72. 1911. 



Idem, Adsorptionsanalyse und chromatographische Methode. Anwendung auf die Chemie 

 des Chlorophylls. Ibid. 24: 384-393. 1906. Idem, Ueber die nachsten Saurederivate der 

 Chlorophylline. Ber. Deutsch. Chem. Ges. 41/: 1352-1354. igoS-Ed. 



c It is difficult to understand this as an explanation. It must not be understood that 

 hemoglobin and chlorophyll are really very much alike; they differ very markedly, but give 

 some of the same decomposition products. It is true that both are related to the interchange, 

 between the organism and its surroundings, of carbon dioxide and oxygen, but the actions of 

 the two substances do not appear to be similar in detail. The author refers here to the fact 

 that they have similar component atomic groups, which may suggest that, in the phylogeny 

 of animals and plants, both groups of organisms may have developed from a common ancestral 

 form having a substance with the characters that are common to hemoglobin and chlorophyll. 

 This is as far as such a theory may go at present. But see below, page 12, et seq. — Ed. 



