BIOLOGICAL TRANSPORT 



The plasma membrane restricts or almost entirely prevents the 

 passive penetration of many solutes. For uncharged hydrophilic 

 solutes, including water to the extent that its diffusion is restrained, 

 the barrier action of the plasma membrane is believed to arise from 

 a compact arrangement within it of the hydrocarbon chains of fatty 

 acid esters, mainly phospholipids. This lipid layer is often pictured 

 as lying between two protein layers in an organized, sandwich struc- 

 ture (cf. Davson and Danielli, 1943). For charged particles an addi- 

 tional barrier action may arise from a repulsion by polyelectrolyte 



1.0 





'o 



3 

 O 



s 



o 



"o 



s 



a 

 E 



S-H 



0.1 



0.01 



0.001 



0.0001 



Methyl alcohol 



Ethyl alcohol | 

 Urethylan 



Urethane 



Triethyl 



citrate 



Cyanamide £ 

 Propionamide A 



Formamide f Pr °P- Blyool 



Acetamide A 

 Glycol # 



• © Trimethyl citrate 

 Antipyrin 

 Valeramide 

 Mpnochlorohydrin 



Diacetin 

 glycerol ethyl ether 

 Diethykirea 

 "Glycerol methyl ether 

 Dimethylurea 



Mor 



v* 



Methylurea 



Urea I 



Methvlolurea 

 ' # Glycerol 



© Monacetin 

 © Ethylurea 



A Thiourea 

 Lactamide ©Diethyl malonamide 

 Urotrophin 



A 1 licvandiamide 



Malonamide 



Erythntol 



0.0001 



0.001 



0.01 



0.1 



1.0 



Partition coefficient 



Figure 4 Permeability of the cells of Chara ceratophylla to non- 

 electrolytes, plotted against olive oil-water partition coefficients. [From 

 ColLmder, R. (1937), Trans. Faraday Soc, 33, 985; with permission.] 



H 



