The next topic that we're going to focus on will be membrane transport. So how exactly do molecules make their way across the cell membrane from one side to the other side of that cell membrane? Well, the method that they use to cross the membrane really depends on the properties of those molecules. So to begin, let's focus on nonpolar and small molecules. So remember, the cell membrane consists predominantly of a hydrophobic region. So the entire core of the membrane, this entire rest section, is hydrophobic nonpolar because of the presence of these hydrocarbon tails, part of the phospholipid molecules.