Toluene crosses pure lipid bilayers many hundreds of times faster than a related compound, phenylalanine. Suggest two different properties of these molecules that would account for this difference.

The lipid bilayer is hydrophobic that is hydrophobic and it can easily cross the lipid bilayer.

Toulene is a hydrophobic and neutral molecule compound so it can easily pass through the bilayer. It is an aromatic compound with a methane group attached to the benzene ring. It is smaller in comparison to Phenylalanine.

Phenylalanine-- It is an amino acid with a benzene ring attached to it. This amino acid is less hydrophobic than the aliphatic amino acids. Because of its less hydrophobic nature, it travels slowly compared to Toluene. It is also larger and has amino and carboxyl groups attached to it. On the other hand, Phenylalanine is a polar compound which has -COOH and -NH2 group. which prevents its delay in its transport across the lipid bilayer.