chapter 3.2

• membranes physically seperate cells from their external environment and allow substances to pass between them
• lipids are the main component of cell membranes
• amphipathic: molecules that have both hydrophilic and hydrophobic regions
• micelles: small spheres of lipid molecules that are formed when fatty acids are hydrolysed
• bilayer: the outer layer of the cell membrane that is made up of phospholipids