The Chloroplast: Its Lamellar Structure 

 and Molecular Organization 



J. J. WOLKEN - 



A basic problem in biology is the conversion and transfer of en- 

 ergy, e.g., light energy to chemical energy or to electrical energy. 

 Recently, research workers have been investigating how the chloro- 

 plast, a differentiated cytoplasmic structure of plant cells, efficiently 

 performs this conversion in the process of photosynthesis. The 

 number of research publications, reviews, and symposia in the past 

 few years on the chloroplast structure and energy-transfer are evi- 

 dence of interest in this exciting problem (Boulder Conference on 

 Biophysics, 1959; Brookhaven Svmposia, 1958; Frey-Wyssling, 1957; 

 Gaffron, 1957; Granick, 1955; ' Miihlethaler, 1955; Thomas, 1955, 

 1958; Wolken, 1959). The purpose, then, of this discussion is to 

 describe the structure and composition of the chloroplast as revealed 

 by microscope studies and chemical analyses, and from the structure 

 and composition to suggest a model for the pigment molecules 

 within the chloroplast; then, if possible, from such a model to specu- 

 late about the molecular structure and function of the chloroplast 

 in energy transfer. 



The photoreceptors of plant cells exist in a variety of shapes and 

 sizes, from those of the photosynthetic bacteria to those of the 

 higher plants. These structures have been given a varied nomen- 

 clature, i.e., chromatophores, megaplasts, plastids, and grana, de- 

 pending on their phylogenetic position and internal organization. 

 Because of inconsistencies in these definitions, even additional 

 nomenclature has been suggested. All of these structures except 



' Aided in part by grants from U. S. P. H. S. Institute Neurological Diseases and 

 Blindness ( B-397 C5), National Council to Combat Blindness (G-199 C7), and the 

 McClintic Endowment. 



^ Biophysical Research Laboratory, Eye and Ear Hospital, and the University of 

 Pittsburgh Medical School, Pittsburgh, Pennsylvania. 



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