BIO 3421 Final- Chapter 3 Membrane Physiology Review Questions and Complete Solutions

PhospolipidsMost abundant membrane component Head contains negatively charged phosphate group (hydrophilic) Two nonpolar fatty acid tails (hydrophobic) Assemble into lipid bilayer with hydrophobic tails in the center and hydrophilic heads in contact with water Fluid - phospholipids held together by van der Waal's forces Cholesterolbetween phospholipids; prevents crystallization of fatty acid chains Maintains fluidity, esp. in cold temperatures Decreases permeability, esp. in warm temps Cold-induced rigidity is countered in some poikilotherms by enriching membrane lipids with polyunsaturated fatty acids. Cholesterol prevents fatty acids chains from packing together, enhancing membrane fluidity. Intergral Membrane Proteinsembedded in lipid bilayer hydrophilic and hydrophobic regions TM proteins extend through the entire thickness of the membrane Peripheral Membrane Proteinsfound on inner or outer surface of membrane Polar molecules Anchored by weak chemical bonds to polar parts of integral proteins or phospholipids Two Models of Membrane Structure1. Fluid mosaic model Membrane proteins float freely in a "sea" of lipids. 2. Membrane-skeleton fence model Mobility of membrane proteins is restricted by the cytoskeleton Some proteins perform specialized functions in specific areas of the plasma membrane Membrane ProteinsChannels- enable ions to pass Carriers- transfer larger substances Receptors- bind specific molecules Docking-marker acceptors- inner surface lock-and-key with secretory vesicles Enzymes - catalyze chemical reactions, inner and outer membrane Cell adhesion molecules (CAMs)- help hold cells together