Would It Dissolve In Oil?

You'll learnwhy a membrane lets a molecule cross based on whether it would dissolve in oil.

A membrane is not a wall with holes in it. It is a band of oil about three nanometres thick, and every question on this topic is really the same one: would this molecule dissolve in that? Ask it in that form and O₂ walks through unaided while a sodium ion smaller than O₂ is stopped cold. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · THE CORE IS THE FILTER · CHARGE > POLARITY > SIZE · IN OSMOSIS, THE WATER MOVES · v5

a band of oil · would this molecule dissolve in it?

Before you start

What you're looking at

One phospholipid, its polar head facing water and its nonpolar tails hiding from it, and then a whole bilayer built from them.

The question

For any molecule at the membrane, the question is not whether it is small enough, but whether it would dissolve in oil.

Step 1 / 12