Week 2 Section Notes

Week 2 Section Notes - Jennifer Phun BICD 110 Section: Wed...

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Jennifer Phun BICD 110 Section: Wed 2-4pm in Center 205 jephun@ucsd.edu OH: 4-5 in Perks Handout 2 Membrane: Lipids and Membrane Proteins Membrane lipids - Properties o Amphipathic o Form the lipid micelle or lipid bilayer o Can laterally diffuse, flex, rotate but CANNOT flip flop o Contain saturated and unsaturated hydrocarbon chains Unsaturated chain allows for flexibility/fluidity o Asymmetry is distributed in lipid bilayer Note: Flippase enzyme help maintain this asymmetric distribution of phospholipids between the membrane leaflets. When there is a loss of asymmetry, the anionic phospholipid (phosphatidylserine) appears on the exoplasm and the overall negative charge hints that flippase is no longer working and indicates apoptosis - Most abundant kind of membrane lipid is the phosphor lipid o Other kids of lipids are cholesterol and glycolipids Cholesterol and Glycolipids - Cholesterol o A kind of membrane lipid molecule o Decreases permeability of lipid bilayer (small H2O soluble molecules) o Prevent membranes from freezing or gelling at cold or hot temperatures - Glycolipids o Lipid molecules that contains sugar molecules o Always present on the outer monolayer of the bilayer Phospholipids - Structure o Polar (hydrophilic) head group: phosphate group, glycerol backbone, choline o 2 hydrocarbon tails, nonpolar hydrophobic - 4 Major phospholipids o Phosphatidylethanolamine o Phosphatidylserine – only phospholipid with overall negative charge o Phosphatidycholine o Spingomyelin o Makes up 50% of all lipids in membranes - Other phospholipid o Phosphatidylinositol o Sphingosine Membrane Proteins interact differently with lipid bilayer - Transmembrane Proteins o Alpha helices Majority are alpha helices 20-30 aa o Beta barrels 10 amm Rigid Different functions: transport receptor, enzymes - Other membrane proteins
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Jennifer Phun BICD 110 Section: Wed 2-4pm in Center 205 jephun@ucsd.edu OH: 4-5 in Perks Handout 2 o Attached to lipid bilayer by covalent linkages
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Week 2 Section Notes - Jennifer Phun BICD 110 Section: Wed...

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