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. hydrogen ion, a charged molecule leucine, a large nonpolar molecule water, a very small polar molecule carbon dioxide, a small nonpolar molecule

Explanation:

According to the text, small nonpolar molecules can cross the lipid bilayer on their own. Ions (like hydrogen ion) and most polar molecules cannot cross easily (but very small polar molecules like water can pass through slowly). Large nonpolar molecules (leucine) cannot fit between the tightly - packed phospholipids. Carbon dioxide is a small nonpolar molecule.

Answer:

C. water, a very small polar molecule; D. carbon dioxide, a small nonpolar molecule