442 p. MITCHELL 



it has been shown that certain osmotic-linkage (active-transport) systems of 

 bacteria may be induced by their substrates in an analogous manner to inducible 

 enzyme systems, and that such systems can be genetically determined since 

 mutants occur which lack them [24]. Although the osmotic and chemical coupling 

 mechanisms may be regarded as formally equivalent, the osmotic linkage systems 

 occupy a dominant position because it is the properties of these systems that 

 control the exchange of substances between the environment and the catalytic 

 and genetic systems of the organism. While a genetic alteration that results in a 

 change of the catalytic and carrier complement of the organism may cause 

 alterations in the efficiency or rate of utilization or sjmthesis of certain com- 

 ponents, which may lead to changes in the concentrations of these components 

 in the organism and indirectly cause changes in the exchange of material with 

 the envirormient, a genetic alteration which gives rise to a change of osmotic 

 coupling through the membrane may cause a direct change in the relationship 

 between the organism and its environment by excluding a substance which 

 might interfere with the catalytic or genetic solids or reactions (and would 

 therefore exert a toxic effect) or by allowing or promoting the entry of a potential 

 substrate. The open systems of enzymes and substrates may be controlled by 

 feed-back mechanisms such as those described by Hinshelwood [25]. In these 

 systems, the direction of the reactions and the state of the system are determined 

 by catalyses channelled by shape relationships between catalysts and substrates 

 which make contact in a single phase. The feedback which can occur by the 

 coupling of the internal catalytic and genetic systems with the osmotic linkage 

 systems regvdating membrane permeabiHty and transport, will give rise to types 

 of stabihzation or adjustment similar to those considered by Hinshelwood, and 

 they would be expected to play a dominant and essential role in the regulation 

 of the relationship between the organism and its envirormient. 



Living organisms are, in effect, complex catalysts which are regenerated by 

 the pressures of certain enviroimiental components. But, the complication of 

 the system required to stabihze both the individual and the lineage would seem 

 to be such that, as Haldane [3] has recently suggested, the occurrence of the first 

 living organisms in the sense of this context must have been very improbable ; 

 or, in other words, it must have taken a long time in an envirormient rich in 

 the appropriate organic and inorganic substances. 



I would like to acknowledge the receipt of a personal grant from the Scottish Hospital 

 Endowments Research Trust. 



REFERENCES 



1. J. B. S. Haldane, Rationalist Annual, 1929, Published in 1933 as Science and Human 



Life, N.Y. 



2. E. ScHRöDiNGER, What is Life ? Cambridge University Press, 1944. 



3. J. B. S. Haldane, Nezv Biol., 16, 12, 1954. 



4. J. D. Watson & F. H. Crick, Nature, Lond., 171, 737, 1953. 



5. J. D. Watson & F. H. Crick, Nature, Lond., 171, 964, 1953. 



6. J. M. Reiner & S. Spiegelman, 7. phys. Chem., 49, 81, 1945. 



7. A. M. Turing, Phil. Trans., 237B, 37, 1952. 



8. L. V. Bertalanffy, Problems of Life. London, 1952. 



9. A. L. DouNCE, Enzymologia, 15, 251, 1952. 



1 

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