Water Builds the Wall It Cannot Cross

You'll learnhow phospholipids in water arrange themselves into a bilayer, heads out and tails hidden inside.

A phospholipid has two personalities: a head that loves water and two tails that cannot stand it. Drop a pile of them into a cell — water on both sides — and they sort themselves into a double sheet, heads out, tails hidden, built by water and barely crossable by it. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · AMPHIPATHIC · HEADS OUT, TAILS IN · THE BILAYER IS A 2-D LIQUID · v5

bilayer · fluid mosaic · water built it

Before you start

What you're looking at

One phospholipid in water: a polar phosphate head and two nonpolar fatty-acid tails.

The question

One molecule loves water at one end and flees it at the other — so how does it settle?

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