Membrane Dissolved Dyes and Steroids

the hydrophobic membrane close to the outer head groups 

the interior of the hydrophobic membrane (in bilayer membranes this region can be subdivided into an inner and outer half) 

the inner regions corresponding to the outer regions 4-1 (9 is called the entrapped water volume) 

Assuming an average microvesicle with an outer diameter of 50 nm, a membrane thickness of 3 nm and a concentration of 10 M lipid molecules corresponding to a 10 M vesicle solution, one obtains volumes of around 3 mL each of entrapped water and hydrophobic lipid membrane per litre of bulk water. 

The permeability of vesicle membranes to glucose is decreased by cholesterol. This steroid stiffens the membrane, making it more hydrophobic. -Sitosterol has a minimal influence. The extra ethyl side-chain also has the effect of 

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