EXPERIMENTS MADE TO ELUCIDATE THE MOLECULAR 

 STRUCTURE OF CHLOROPLASTS 

 Wilhelm Menke 



It has been known at least since 1940 that the chloroplasts possess a lamel- 

 lar fine structure*^' ' ' ''. It has also been known since that time that the 

 grana are not independent structural elements, but differentiations of the 

 lamellar system^; Not until 20 years later was the general morphological 

 structural principle of the lamellar system discoveredP' ^' '' "• ^'. Fig. 1 

 shows the most important types of these lamellar systems in bacteria, cyano- 

 phyceae, algae and higher plants in schematic representation. The structural 



O O o ° o °0 



o?°o°°o°§°o°o°o 



Fig. 1. Main types of the photosynthetic lamellar system. 



a- Purple bacteria; b- Cyanophyceae and Rhodophyceae; 



c- Grana-free chloroplasts; d- Grana -containing chloroplasts 



elements of the lamellar system are in every case membranes closed sack- 

 like in themselves, for which I have suggested the name "thylakoids". Thyla- 

 koids are usually flattened, but may sometimes be swollen like vesicles. We 

 know that the photochemical reactions of photosynthesis and electron trans- 

 port take place within the thylakoid membranes^ '. 



A certain uniformity in chemical structure appears to correspond to the 

 uniform morphological structure principle. Thylakoids consist of proteins, 

 lipids and a nvimber of other compounds. After the extraction of the lipids 

 (about 45-48% of the dry weight) and washing of the residue with water and 

 saline solutions about 52-55% of the dry weight of the thylakoids remains. 

 This contains about 80-85% amino acid residues, 8-10% carbohydrates and 1% 

 nucleotides. Part of the carbohydrates - among which arabinose and galac- 

 tose predominate - can be split off by treatment with phenol. The amino acid 

 composition of the lamellar structural protein thus obtained is remarkably 



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