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. Whic of the following has the lowest rate of diffusion across an artificial membrane?

A. glycerol
B. glucose
C. ethanol
D. water

The cell membrane is made up of lipid bilayer and proteins are embedded or may span the lipid bilayer. The carbohydrates are present in association with lipids and proteins.

The artificial membrane has been prepared that are free from proteins. Small uncharged particles may easily diffuse through the membrane. Among the given molecules in the question water is the smallest molecule and diffuse out first through the plasma membrane. Ethanol is 2 carbon compound and diffuse after water than glycerol diffuses as it is a 3 carbon compound. Glucose is the largest molecule and diffuse last through the plasma membrane.

Thus, the correct answer is option (A).