We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any protein components. Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees. Which of the following has the lowest rate of diffusion across an artificial membrane?
A. ethanol
B. the ions Na+ and K+
C. glycerol
D. water
E. glucose and sucrose