L4_4_7_11 - Tuesday: Ch. 12 p695-704 & 723-745 Ch. 6,...

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Tuesday: Ch. 6, p388-399 Principles of Membranes Membrane Transport 2cd problem set is up on the web. 1 st problem set key is on the web. In my office hours yesterday, a student raised questions about the #4 (ORC IP) and I address alternate explanations in the key. I also posted a sample exam 1 from last year. There was no audio Tuesday, therefore no podcast. Media services knows Learning Support Services (LSS) has hired a tutor for Bio110, Diana Summers– dsummer@ucsc.edu Students are eligible for up to one-hour of tutoring per week per course, and may sign-up for tutoring at https://eop.sa.ucsc.edu/OTSS/tutorsignup/
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The are 4 kinds of phospholipids Sphingomyelin is built from Sphingosine not glycerol choline phosphate glycerol PE has smaller head group than PC, leads to triangular shape PE PC
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Saturated lipids pack more tightly and decrease fluidity Figure 10-12 Molecular Biology of the Cell (© Garland Science 2008)
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Cholesterol fits between phospholipids changes permeability but not fluidity Decreases permeability decrease fluidity Inhibits HC chain aggregation increase fluidity
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Lipid bilayers are asymmetric
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Proteins can be associated with lipid bilayers in different ways Integral: transmembrane, or held in the membrane by lipid group or hydrophobic polypeptide region.
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The alpha helix is the most commonly used protein secondary structure used to cross membranes Forms when a single polypeptide chain twists around itself to form a rigid cylinder A hydrogen bond forms between every 4th poly- peptide, linking C=O of one peptide bond to the N-H of another All the N-H groups point up and all the C=O groups point down, giving a polarity to the helix C-terminus -> negative N-terminus -> positive
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Beta sheets Interaction between H- bonds between peptide bonds in different strands Either parallel chains of neighboring polypeptides or Single polypeptide that has folded back on itself (anti-parallel) Amino acid side chains in each strand alternatively project above and below the plane of the sheet Largely restricted to outer membranes of bacteria, chloroplasts and mitochondrias
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Beta barrels are also used to create protein structures that cross membranes (I) Receptor for bacterial virus Lipase
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Beta barrels are also used to create protein structures that cross membranes (II) Iron Transporter Water filled pores What kind of aa line the pore?
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An experiment that demonstrates that some membrane proteins are free to diffuse in the membrane
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Another experiment that demonstrates that some membrane proteins are free to diffuse in the membrane
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Some proteins are confined to specific domains in the membrane
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Four different ways that membrane proteins can have their mobility restricted by protein-protein interaction
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membrane due to the cortical cytoskeleton Spectrin: self associate head to head to form 200nm long tetramer Ankyrin: links spectrin to transmembrane band 3 Band 4.1: links spectrin and actin to transmembrane band 3 and transmembrane glycophorin
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This note was uploaded on 02/06/2012 for the course BIO 110 taught by Professor Rexach during the Fall '08 term at University of California, Santa Cruz.

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L4_4_7_11 - Tuesday: Ch. 12 p695-704 & 723-745 Ch. 6,...

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