GROWTH 259 



and therefore, they must have different sets of enzjones 

 for each source, and probably a fairly large number of 

 molecules of each kind. 



By applying this same method of calculation to the 

 data on p. 105, it can be shown that a yeast cell will 

 ferment about fifty million glucose molecules per second, 

 and Micrococcus ureae as many as eighteen million urea 

 molecules per second. 



Number of Growth Catalysts per Cell. — The real 

 growth mechanism of the cells is centered in the chromo- 

 somes. These are the growth catalysts. They are 

 believed to consist of sub-units, called genes, which are 

 beyond microscopic visibility. Each gene is supposed 

 to be the catalyst for one specific reaction or property 

 in the organism, and therefore, each gene must be 

 chemically different from all other genes (unless we are 

 dealing with multiple sets of chromosomes). 



The size of the genes has not been measured. We 

 know only that it is below the dissolving power of the 

 microscope, i.e., smaller than 100 m/z. The size of 

 the molecules of which the chromosomes are composed 

 is not known either, but of many other proteins, the 

 molecular radius has been determined by the Svedberg 

 method. The author is indebted to Dr. D. C. Carpenter, 

 of the Geneva (N. Y.) Experiment Station, for the 

 compilation of Table 73. The proteins marked with 

 a star are known to have nearly spherical molecules. 



The diameter of these more common proteins goes 

 as high as 24 m^. The molecules of the chromosomes 

 are much more remarkable than these, because they 

 control the most complicated synthesis of the many 

 different cell substances from simple food. It is probable 

 (though it is not necessary) that molecules which bring 

 about the synthesis of protein are more complex than 



