The document discusses the structure and functions of cell membranes. It notes that membranes are composed of phospholipids, glycolipids, cholesterol and proteins. Membranes form a selectively permeable barrier and establish concentration gradients. They localize enzymes and processes like transport, signaling, endocytosis and exocytosis. The fluid mosaic model describes membranes as a fluid structure with proteins embedded and diffusing. Membrane composition and fluidity impact functions like signaling, vesicle movement and cell division.

6. Structure of the Plasma Membrane

28. http://www.biochem.arizona.edu/classes/bioc462/462a/NOTES/LIPIDS/diff.html Membranes are fluid structures