And so that means nonpolar molecules, no matter how large, will be able to move across. And that's exactly why cholesterol, which is a large molecule, has no problem moving across our cell membrane. But even a very small atom that has a full positive or full negative charge, such as the sodium atom, will not be able to move across because it is very polar. It contains a full charge. So we see that the two things we should consider when determining whether a given molecule can make it across the phospholipid bilayer is the size of it and the polarity. And we have to weigh the two things together.