Final answer:
Hydrophilic molecules cannot easily pass through the cell membrane because they are attracted to water. The hydrophobic interior of the phospholipid bilayer repels these molecules.
Step-by-step explanation:
Molecules that are hydrophilic, such as polar and charged molecules, cannot easily pass through the cell membrane because they are attracted to water. The plasma membrane is made up of a phospholipid bilayer, which has a hydrophobic interior. Hydrophilic molecules are repelled by the hydrophobic tails of the phospholipids and therefore cannot cross the membrane easily.