Questions: Which of the following will pass through a cell membrane most easily? Multiple Choice Small polar molecules Small nonpolar molecules Large polar molecules Large nonpolar molecules Large neutral molecules

The answer is the second one: Small nonpolar molecules.

Explanation for each option:

1. Small polar molecules: While small in size, polar molecules have partial charges that can interact with the hydrophobic core of the lipid bilayer, making it more difficult for them to pass through the cell membrane without assistance.

2. Small nonpolar molecules: These molecules can pass through the cell membrane most easily because the lipid bilayer is hydrophobic, and nonpolar molecules do not have charges that would impede their movement through the membrane.

3. Large polar molecules: These molecules face significant difficulty passing through the cell membrane due to both their size and their polar nature, which interacts unfavorably with the hydrophobic core of the membrane.

4. Large nonpolar molecules: Although nonpolar, their large size makes it difficult for them to pass through the cell membrane without assistance, such as transport proteins.

5. Large neutral molecules: Similar to large nonpolar molecules, their size is a barrier to easy passage through the cell membrane, even if they are neutral.

In summary, small nonpolar molecules pass through the cell membrane most easily due to their compatibility with the hydrophobic nature of the lipid bilayer and their small size.