Phospholipid bilayer

Phospholipid bilayer 

The head group points towards the outside of the membrane while the tail group is hydrophobic and points inward. There are some very common fatty acid side chains (R groups: R1 and R2) including:

1. palmitate, 16 carbon saturated fatty acid chain.
2. oleate, an 18 carbon unsaturated fatty acid chain with a single double bond.
3. sterate, an 18 carbon saturated fatty acid chain.

Saturated bonds are very flexible but double bonds create kinks and limit flexibility.

Phospholipids have a amphipathic property or nonpolar and polar properties.