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Lecture 16 Biological Membranes

Lecture 16 Biological Membranes - Describe the essential...

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Describe the essential role of membranes in selective permeability, selective uptake, and secretion, compartmentalization, scaffolding for complex reactions, and as sites for signal transduction pathways Name the typical membrane localization of phospholipids, cholesterol, and lipopolysaccharide (LPS) Explain how the distribution of phospholipids and proteins and influences the membrane permeability of ions, hydrophilic, and hydrophobic compounds Explain that membranes behave as two-dimensional fluids that are made more rigid by cholesterol and more fluid by unsaturated fatty acids Recognize that membranes are typically about 50% lipid and 50% protein, most membrane proteins are glycosylated, and the ABO blood group antigens are the results of differing glycolipids on red blood cells Vocab: Phospholipids, cholesterol, active transport, transporters, channels, P- glycoprotein, aquaporins Outline: Function of biological membrane Structure of biological membrane Transport across biological membranes - Biological membranes: barriers o Shell that compartmentalize specific chemical processes o It serves as barrier 1) information (receiving info) 2) chemical (import/export of molecules) 3) motility (capacity for movement and expansion) o cell membrane concentrates biological process together inside the cell: 50% cytosol 50% membrane 5% plasma membrane 95% other o Two dimensional fluid Membranes form a 2-D fluid with proteins surrounded by lipids Embedded in the fluid mosaic model are proteins (transmembrane protein) Not all the protein rapidly diffuses but most of them do Some lipid draft/protein in the micro domain cannot diffuse Lipids bi layer – hydrophobic end, cannot hydrogen bond and that’s what drive the formation Lipids spontaneously assemble into two dimensional fluids because of hydrophobic effect o b/c of the lack of H-bond o lipid can rotate/move around except flip to the other leftlet b/c thats energetically unfavorable fluidity of the membrane is based on the number of double bonds kinks in the HC chain - Phospholipids o o 4 m ajor classes Phosph atidylcholine Sphingo myelin (neg atively charged) Phosph atidylserine Phosph atidylethanola mine o one is neg ative o m ost ar e n eutral
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