28&30SeptemberNotes.pdf LIFE 210
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This 3 page Class Notes was uploaded by Mikaela Maldonado on Wednesday September 30, 2015. The Class Notes belongs to LIFE 210 at Colorado State University taught by Paul J Laybourn in Fall 2015. Since its upload, it has received 91 views. For similar materials see Introductory Eukaryotic Cell Biology in Entomology at Colorado State University.
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Date Created: 09/30/15
Use with posted power points on Canvas for full notes Membrane Structure Cytosolic means inside the cell Exoplasmic means outside the cell Net negative charge on the BE SURE To REVIEW MATERIAL ON LIPID HEADS AND BACKBONES FROM LAST LECTURE have sugars in their composition Asymmetrical lipid bilayer gt gt gt Two layersso things are not evenly distributed between the layers Distribution between the inside and outside has different charges and proportions on the bilayer Inside net negative charge but outside has a neutral charge n apoptosis the charges flippedrecitation questions about flipase Sugars complex on the outside of cell membranes and can have a little negative charge that can be used for cell recognition Asymmetry also exists on a 2D planehow it looks on the surface Bits of membrane can float together on the surface of the cell as welllipid raft Sphingosphine has longer fatty acid tails making the membranes a little thicker Sugars form bonds between carboxyl groups and form rafts as wellcholesterol likes to stick between the phospholipids just below the phosphate head commonly in the racks Membrane lipid diffusion and fluidity Fluid mosaic but not always constant Rotational diffusionbreak van der waals spin Translationalmove on a 2D plane Transmembrane diffusion rarely occursneed an enzyme Flexion is wiggling of the fatty acid tails Fluidity dependent on Temperature direct correlation O Paracrystallindecrease temp decrease fluidity Acid tail saturation O Sticks together and keeps tails in a more rigid positiondecrease in fluidity because there are less kinks in tails and allow a more tight connection with more saturation Cholesterol O Regulate permeability on lipid racks plug decrease permeability of polar molecules O Decreases temp where it solidifies O More cholesterol keeps it more fluid at lower temperatures gt Clicker Question The organism likely to have the highest percentage of unsaturated fatty acid chains in membranes is O Antarctic fishfluid membranes allow greater fluidity at lower temperatures O Desert iguana O Human O Polar bear O Thermophilic bacteria Clicker Questions Cholesterol is essential for lipid raft formation because gt Sphingolipids will pack together too closely gt Glycerophospholipids will pack together too closely without cholesterol gt Sphingolipids have large head groupshuge sugar complex for the head leaves gaps between the tails that the cholesterol has to fill in gt Sphingolipids have small head groups gt Glycerophospholipids have large head groups Lipid bilayers are permeability barriers for polar molecules Permeability depends on size polarity and if has a charge gt Lipid bilayer structure relates to functional groups and interactions Energy of solute passage delta G gt Rate is dependent on energy of transition state S gt Can be a transfer from inside to outside the cell and relates to the delta G of the reaction difference of G from beginning to end and delta G gt Delta G is lowest for nonpolar 5 molecules highest with charged 5 moledules delta G of concentration gradient across membranes gt electrochemical gradientchange in charges between molecules and varies with concentration gt delta G mostly due to transition state delta 5 gt DeltaGRTlnSinSout if SoutgtSin and inoutlt0 so delta Glt0 gt Gives free energy difference across transport Clicker Question Membrane electrochemical gradients involve both charge and concentration components with regard to NA but not K in most mammalian cells gt Not regards to K because charge differential potassium has a concentration difference but charges are irrelevant Gated ion channels are essentially holes in a membrane CLICKER The delta G for a molecule can be at equilibrium across a lipid bilayer and yet have different concentrations on one side than the other TRUE CLICKER the Cells A and B are the same size shape and temperature but cell A is metabolically quiet and cell B is actively consuming oxygen More oxygen will diffuse into cell B because the concentration gradient into cell B is steeper Lipid bilayersmembranes are permeability barriers gt Molecules can cross by simple passive diffusion gt Molecules can cross through channel and carrier proteins I Carrier proteins have a binding site that they transfer molecules through I Kind of looks like a kidnapping that a partner in crime releases on the other side Membrane proteins structure dictated by hydrophobic environment side note this hydrophobic stuff seems to come up a lot Glucose transportgut lumen to blood Transport can be passive or active gt Passivediffusion delta G with concentration or charge gradient I Channels or carrier proteins I Occurs all the time naturally wanting to equalize the gradient gt Activedelta G against concentration or charge gradient up hill I Primary activeuses NRG source directly Coupling reactions ATP Light driven pump I Secondary active uses NRG indirectly Concentration gradient using a primary active transporter Electrochemicalgradient Membrane permeability simple diffusion Passive gt Hydrophobic core free diffusion I Nonpolar gases hydrophobic molecules oxygen C02 N2 benzene gt EtOH small uncharged polar molecules h20 urea glycerol slow diffusion gt Large uncharged polar molecules like glucose and sucrose can be under VERY slow diffusion gt Charged ions H NAetc no diffusion gt All the slower reactions and ones without any diffusion are the ones that would require transporters gt CLICKER Question The correct order of these molecules for the ability to cross lipid bilayers from most to least readily is I C02 gtethanolgtH20gtglucosegt Ca2gt RNA I RNA has a backbone of ribose and phosphates and has a chargeRNA only leaves the cell with help of something else