ENZYME ACTION 



87 



t£X> 



and fats — are utilized by the living cell as such : through enzyme 

 action, whether extracellular or intracellular, they are broken 

 down into simpler substances, into their component radicles. 

 The evidence is accumulating yearly more and more that, if 

 not the enzymes themselves, at least the zymogens, the bodies 

 from which the enzymes are derived, originate in, and are dis- 

 charged from, the nucleus, the dynamic centre of the cell. 1 

 Already there is evidence that certain of the amino-acids, and 

 it may well be of groups of conjugated amino-acids, constituting 

 Fischer's polypeptids, manifest enzyme action. Their amphoteric 

 constitution in itself favours the possession of these properties. 



We can visualize the pro- 

 pi A. 



cess thus : Let A represent 



a peptone or polypeptid 

 molecule of food-stuff small 

 enough to be absorbed or 

 diffused from the external 

 medium into the cytoplasm 

 of the cell. This may either 

 (1) be broken down into 

 simpler radicles, a', a", a'", 

 and those radicles utilized by 

 a direct dissociation process 

 for the growth of the pro- 

 teins of the cytoplasm (B, Fig. 7) or, it may be, 

 nuclear biophoric molecules themselves ; B, through 



unsatisfied linkage (&'), exer 



*J' 0!" 



Fig. 7. 



the 



an 



~~~\^ C a „«*,A,a- 



cising a stronger attraction 

 for certain of the constituent 

 radicles of A, such as a', in 

 which case a' becomes part 

 and parcel of B, and a" and 

 a'", whether combined or 

 loosened, are left free in the 

 cytoplasm. Or (2) where the 

 conformation (that is to say, 

 constitution) of A and of B 

 (or better A' and B') is not 

 such as to permit of this direct attraction and linkage, it may 

 1 See the address upon " The Dominance of the Nucleus," Pt. II. Chap. V. 



Fig. 8. 



