Question

this arrangement prevents certain molecules from crossing the lipid bilayer on their own. the phospholipids are tightly packed, which means large molecules cannot fit between them. small nonpolar molecules can cross, but ions and most polar molecules cannot cross because they are repelled by the nonpolar fatty acid tails. some very small polar molecules, like water, are able to pass through, but they do so at a slow rate. which of the following molecules can pass through the lipid bilayer without assistance? select all that apply. water, a very small polar molecule sodium ion, a charged molecule glucose, a large polar molecule oxygen, a small nonpolar molecule

Explanation:

According to the text, small nonpolar molecules can cross the lipid bilayer on their own. Water (a very small polar molecule) can pass through at a slow rate without assistance. Sodium ion (a charged molecule) and most polar molecules (like glucose, a large polar molecule) cannot cross because ions are repelled and large polar molecules are either repelled (if polar) or too big. Oxygen (a small nonpolar molecule) fits the criterion of molecules that can cross without assistance.

Answer:

water, a very small polar molecule; oxygen, a small nonpolar molecule