L4 - Thursday: Ch. 12 p695-704 & 723-745 Ch. 6, p388-399...

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Technical difficulties have prevented the visual portion of the podcast but the audio is available. Media services says they have it fixed now https://media4.ucsc.edu/webcast/ Thursday: Ch. 6, p388-399 Principles of Membranes Membrane Transport 2cd problem set is up on the web There is a student in class who needs a notetaker. It is a paid position through the DRC, so you should contact them directly, at 146 Hahn Student Services, 459-2089
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The are 4 kinds of phospholipids Sphingosine Not glycerol
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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
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Lipid bilayers are asymmetric
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Proteins can be associated with lipid bilayers in different ways
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Membrane-spanning alpha helices can be detected by a computer algorithm The free energy needed to transfer successive segments of polypeptide from a nonpolar solvent to water is calculated from the aa composition using data obtained from model compounds. Calculation made on segments (10-20aa) Positive values indicates that free energy was required for transfer to water (i.e. the segment is hydrophobic). Peaks that are ~20aa long indicate α -helix spanning membrane
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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 H- bonds between peptide bonds in different strands Either parallel chains of neighboring polypeptides or Single polypeptide that has folded back on itself (anti-parellel) Amino acid side chains in each strand alternatively project above and below the plane of the sheet
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Beta barrels are also used to create protein structures that cross membranes
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Beta barrels are also used to create protein structures that cross membranes
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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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Some proteins have restricted mobility in the membrane due to the cortical cytoskeleton
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EM showing stretched 10Xcytosolic side of a red blood cell membrane
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Cortical cytoskeleton can coral proteins
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Chapter 11: Principles of Membrane Transport
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Lipid bilayers are impermeable to many molecules cystinuria
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Cells use special proteins to transport small molecules across membranes
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In the case of single uncharged molecule, passive transport simply depends on the difference in concentration on 2 sides of the membrane Driven by ATP Driven by concentration gradient pumps
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If the solute carries a net charge , concentration AND charge determine the energy requirements for transport across membranes
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This note was uploaded on 03/28/2010 for the course MCD BIO 110 taught by Professor Hinck during the Fall '09 term at University of California, Santa Cruz.

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L4 - Thursday: Ch. 12 p695-704 & 723-745 Ch. 6, p388-399...

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