Phosphorus and Life 1 



By D. P. Hopkins, B. Sc, F. R. I. C. 



Or the truly mineral elements — those found in the earth's crust of 

 rock — phosphorus undoubtedly has the greatest biological significance. 

 In the strictest sense of objectivity all elements that are essential for 

 the growth and maintenance of living matter are equally important 

 whether required in large or small amounts. However, the major 

 role of phosphorus has compelled special attention since the first days 

 of nutritional and agricultural science, and centuries before scientific 

 interpretation was possible the vital importance of materials contain- 

 ing phosphorus was widely known. 



The natural occurrence of elementary phosphorus is exceedingly 

 rare and transient, for it combines spontaneously and vigorously with 

 oxygen. Even the oxide that is formed, the pentoxide, has a very 

 brief existence, for it rapidly absorbs water and combines with it to 

 produce phosphoric acid. It is as simple or complex phosphates, 

 which are the salts of phosphoric acid, that most of the world's supply 

 of phosphorus is distributed. A proportion of the earth's phosphorus 

 is continually passing out of the mineral reserve into living matter ; 

 similarly, phosphorus is continually passing out of living matter and 

 re-entering the mineral reserve. These circulations take place within 

 two cycles, a land cycle and a marine cycle. Although each of these 

 cycles can be separately described, they are in fact interconnected; 

 indeed, losses of phosphorus from one cycle become gains for the other. 



The initial source of the world's phosphorus was the sun. Spectro- 

 scopic analysis shows that the sun's atmosphere is fairly high in 

 phosphorus content. In the formation of the earth by the condensa- 

 tion of solar matter, much of the phosphorus then present was en- 

 veloped in the earth's outer shell of siliceous matter. All igneous 

 rock contains phosphorus, mainly as apatite, a complex form of cal- 

 cium phosphate. The first biological organization of matter took 

 place in the seas and the marine cycle of phosphorus utilization long 

 preceded the land cycle. 



If the silicate rock surface of the earth imprisoned solar phosphorus, 

 so, too, the large water surfaces must have acquired some supplies of 



• * Reprinted by permission from Discovery, vol. 13, No. 8, March 1952. 



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