The major type of lipid found in plasma membranes are phospholipids. Phospholipids are amphipathic molecules, consisting of two hydrophobic fatty acid chain tails connected to a polar phosphate-containing hydrophilic head. The tails differ in length (usually between 14 and 24 carbon atoms), and one tail usually has a cis double bond while the other does not. Each double bond in the tail creates a small kink.
The lipid bilayer's phospholipid structure is made of tightly packed molecules and can form different shapes. For example, they can be wedge or cylinder shaped. The more closed and compact the phospholipids are,