Membrane - Biochemistry - Lecture Slides, Slides of Biochemistry

Download Membrane - Biochemistry - Lecture Slides and more Slides Biochemistry in PDF only on Docsity! Docsity.com What is a membrane? A water-induced structure composed of a lipid bilayer and integral and peripheral proteins What holds a membrane together? Hydrophobic interactions between the non-polar hydrocarbon chains of the lipids and proteins What proteins are in a cell membrane? Two types: integral and peripheral Are proteins capable of movement Yes, the protein float on a sea of lipid much the same as apples bobbing on water Docsity.com Asymmetric Distribution in Human Erythrocytes Phospholipid Inner Outer Sphingomyelin 7 21 Phosphtidylcholine 9 23 Phosphatidylethanolamine 25 6 Phosphatidylserine 9 0 Total 50 50 Docsity.com Unit Membrane Hypothesis • All membranes follow the same basic dimensions • A membrane is composed of a lipid bilayer • Membrane lipids are oriented to allow polar portions to be directed away from the bilayer • Membrane Proteins can be peripheral (surface) or integral (through) Docsity.com All Membranes appear Trilaminar (3 layer) When stained with OsO4 and examined in the electron microscope, all membranes show two dense layers on the outer and inner surfaces separated by a less dense central region Docsity.com Fluid-Mosaic Model • Membrane is fluid • Proteins float on a sea of lipid • Membrane proteins diffuse laterally • Membrane proteins do not cross the membrane • Proteins are in constant motion Singer and Nicolson Docsity.com Photobleaching >. ——v Unbleached molé, es enter Cell Lazer Docsity.com FAST SLOW Flip-Flop (Flipases) Lateral Lipid Mobility Docsity.com