Why is the structure of the cell membrane referred to as bilayer?

Question

Why is the structure of the cell membrane referred to as bilayer?

Answer 1

The cell membrane is referred to as the lipid bilayer because it literally resembles 2 layers. The membrane is composed of phospholipids. Each phospholipid has a phosphate head with lipid tails. The lipid tails are water-fearing, or hydrophobic, and the phosphate heads are hydrophilic, or water-seeking. Therefore, it would make sense, because the cell's outside and inside contains water, to have the fatty tails not touch any water at all and have all the phosphate heads contact the water. In order to do this, 2 layers must be created, like so:

ooooooooo

| | | | |  | | | |

| | | | |  | | | |

ooooooooo

o = phospholipid head

| = phospholipid tail

Answer 2

Because it is made up of 2 layers of phospholipids. Phospholipids look like sperm actually - circles with tails. The tails go on the inside because they are hydrophobic and the heads go on the outside because they are hydrophillic.