Most organic solutes cross epithelial membranes by simple diffusion on the lumen side followed by active transport across the blood side of the membrane.

Question

Quizplus · Accepted Answer

Most organic solutes cross epithelial membranes by active transport on both the lumen and blood sides of the membrane, rather than simple diffusion on the lumen side. Simple diffusion is only efficient for small, nonpolar molecules. Active transport mechanisms are necessary to move larger, polar molecules and maintain concentration gradients.

Most Organic Solutes Cross Epithelial Membranes by Simple Diffusion on the Lumen