Which statement about transcellular transport is correct?

• A. Transcellular transport depends more on hydrophobicity than molecular weight
• B. Transcellular transport depends more on molecular weight than hydrophobicity
• C. Transcellular transport depends on active transport
• D. Transcellular transport is independent of molecular properties

Answer: (A)

Crossing through the cell membrane is the key step in transcellular transport, so what matters most is how well a molecule partitions into and moves through the lipid bilayer. Lipid solubility, or hydrophobicity, largely dictates how readily a substance can enter the membrane and diffuse to the other side. Molecular weight does influence how fast diffusion happens, but it does not drive the basic ability to permeate the membrane as strongly as lipophilicity does. Ionized or very polar molecules don’t cross easily unless active transport or specific carriers are involved, but that’s not the general route for most transcellular movement. So hydrophobicity being the primary determinant for passive transcellular diffusion makes sense, with molecular weight playing a secondary role.