The lipid bilayer Most abundant are phospholipids. They have a polar head group and two hydrophobic tails. Cholesterol Cholesterol has a small hydroxyl polar head group followed by three rigid, steroid ring structures. Phospholipids 4 main types in mammalian plasma membranes. Membrane proteins can be separated from lipid bilayers by solubilizing in detrergents.
Membrane proteins are also able to diffuse in the plane of the membrane.