1.- A "crystalline" bilayer is constructed by repeating a single phospholipid:

 We start with a phosphatidylcholine molecule (PC), in which the terminal carbons are highlighted. All molecules in this presentation have their hydrogen atoms omitted in order to simplify the display.

we see 4 of these molecules, and let's them.

When grouping to form a membrane, the hydrophobic fatty acid "tails" or "legs" of each PC molecule fit between the "legs" of another molecule, so avoiding interaction with aqueous medium:

We have this compact group of 4 phospholipids; let's colour by atom type ( C O N P, called the Corey-Pauling-Koltun, or CPK, model), and with different colours to differentiate palmitic and oleic chains: . Let's highlight nitrogen (in choline) and phosphorus atoms: . Let's so we look down on tops (polar head).

Now let's make 4 more copies of this phospholipid tetrad into a tight-fitting row of 20 phospholipid molecules: . Let's and change to with CPK colour.

Diverse representations:

 So, we have a double row of 20 phospholipids (with phosphorus atoms highlighted). By copying it, a small bilayer with 40 phospholipid molecules is obtained flanked by water molecules

Let's remove the water and leave only the 40 phosphorus atoms, so we can see how they are arranged: