Which of the following will pass through a cell membrane most easily? A) small polar molecules B) small nonpolar molecules C) large polar molecules D) large nonpolar molecules E) large neutral molecules

B) small non-polar molecules. Small molecules can pass through the cell membrane through diffusion (does not require energy). The molecule being non-polar is an advantage because the tails of the phospholipid bilayer is hydrophobic (nonpolar), so it does not repel nonpolar molecules.