BIOLCHEM 415 1st Edition Lecture 10Outline of Last Lecture I. Myoglobin and hemoglobin – crystal structures and oxygen binding propertiesII. Hemoglobin’s cooperativity in binding O2III. Allosteric regulation of hemoglobin that controls its O2 binding properties Sickle Cell Anemia and MalariaOutline of Current Lecture IV. Biological membranes and their compositionV. Lipids physical propertiesVI. Transport ProteinsVII. Channels and pumpsCurrent LectureMembranes- separate/protect from environment- controls “internal milieu”- cell (plasma) membrane- all organelles have membranes- controls the organelles environment and affects functionMembrane Lipids- physical properties- amphipathic molecules- hydrophobic (nonpolar) tails and hydrophilic (polar) heads- lipid bilayer forms- lipid vesicle (liposome)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- polar heads face outside and inner aqueous compartment- nonpolar tails inside of the membrane-inner aqueous compartment formed- cells are like large liposomes- interior of cell extremely large in comparison to membrane- membrane curvature is negligibleMembrane flexibility- dependent on composition and temperature- saturated fatty acids react strongly with each other- decreases fluidity- stearic acid- has a higher Tm- double bonds keep membrane from packing tightly- increases fluidity- oleic acid- has a lower Tm- cholesterol- mitigates fluidity changes with temperature- at higher temps keeps fluidity from dramatically increasing- at lower temps keeps fluidity from decreasing by maintaining fluidity, prevents gellingMembrane’s hydrophobic core- permeability is limited- ions and polar molecules can’t pass through- also impermeable to polar heads of the lipids- allows rapid lateral diffusion but prevents transverse diffusion- 1 sec for lateral diffusion while several hours for transverseFRAP- Fluorescent Recovery After Photobleaching- analyze particle movement in the membraneMembrane barrier v. communication- nutrients and ions need to get in and out - proteins helpIntegral Membrane Proteins- interact with hydrocarbon chains- most span the length of the membrane- 20 amino acids can transverse a bilayer- 7 membrane spanning α-helices are a common motif- asymmetrically distributed Peripheral Proteins- on membrane surface- associate electrostatically with polar heads or integral proteins- membrane localization crucial- occasionally covalent links tether proteins to hydrophobic core of membrane- Transporters and pumps- ATP- driven pumps- p-type ATPases- ABC transporters- secondary transporters/cotransporters- don’t use ATP directlyATP Binding Cassette (ABC) transporters- hydrolyze ATP for transport energySecondary Transporters- use the concentration gradients- cancotransport another compound- antiporter: travels opposite transported molecule- symporter: travels in same direction as transported moleculeChannels - open or close to control flow of ions or molecular downhill their concentration gradient- K+ Channel- membrane potential- moves interior to exterior- only move K+- not even smaller ions (i.e. Na+)- dehydrate K+ in order to pass selectivity filter through- Na+ can’t be
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