Which statement concerning the structure and function of the biological membrane is true?
A. Biological membranes are primarily composed of protein with a small layer of lipid on both the inner and outer surfaces
B. Lipid-soluble compounds tend to diffuse through biological membranes faster than water-soluble ones
C. The rate at which lipid-soluble substances pass through biological membranes is determined by the size of the diffusing particle
D. All of the above
Since biological membranes are primarily a sandwich composed of a bimolecular layer of lipid with a layer of protein on both the inner and outer surfaces, lipid-soluble compounds diffuse through it faster than water-soluble compounds. For water-soluble compounds, the size of the molecule is the rate-limiting factor in diffusion.