What Kinds of Molecules Pass Through a Cell Membrane Most

Question

What kinds of molecules pass through a cell membrane most easily?
A) large and hydrophobic
B) small and hydrophobic
C) large polar
D) ionic
E) monosaccharides such as glucose

Accepted Answer

Small and hydrophobic molecules pass through a cell membrane most easily because they can dissolve in the phospholipid bilayer of the membrane, which is also hydrophobic. This allows them to move across the membrane without the need for assistance from transport proteins or other mechanisms. Large polar molecules, ionic molecules, and monosaccharides such as glucose cannot pass through the membrane as easily because they cannot dissolve in the hydrophobic interior of the membrane.