50 Discussion 



macromolecules which are very often stable in one dimension, along a 

 chain. You have covalent bonds in the chain which give great stability. 

 And yet the relationships between adjacent chains are based upon hydro- 

 gen bonding, and have almost the same lability as water; so you have 

 this curious compromise between absolute rigidity and great lability. I 

 think the extraordinary plasticity of living cells depends on this sort of 

 thing. 



Bourne: Does this plasticity, which I suppose is represented by the 

 rate of flow in and out of molecules and compounds, vary between old 

 and young cells ? 



Danielli : I do not know. 



Bourne: In a sense the processes that are going on in the cell are com- 

 parable with an eddy in a molecular whirlpool, and it is only the pattern 

 of the eddy which is constant, with perhaps the pentose nucleic acids 

 sticking out like rocks in a rapids. 



