Lecture 2 - includes txtbk reading (pg. 144-146) notes & ATPase youtube notes

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University of Toronto St. George
Cell and Systems Biology
Melanie Woodin

CSB332 L2 Ch 456 Jan 11 2012Allowed to post recordings on the portal discussion but not anywhere else2 classes of recsIf ligand binds to channeldirectly opensionotropicIf ligand binds to rec that initiates signal cascade that opens another channelmetabotropicAch rectransmembrane 5 indiv subunits composition of subunits types can very always 2 alpha subunits where Ach always bindsMuscarinic Ach recmetabotropicNicotinic AchionotropicRec named for ligand that can bind even if not how normally activatedCharacterizaed by ray torpedodensely packed Ach recs so large sourceEach subunitlong chain of aasAminocarboxyl ends in extracellularLoop in cytoplasmTransmembranespanning domainsM2most importantcontains aas for channel selectivityEach subunit has M2M2 line the poredetermine which cations can flow thruWhen openedM2 rotate outwardsopensIf looking from extracellular downM2 lining pore5 subunitsA channel closed pore smallB larger pore M2 transmembranedomain rotated outwardC M2 close closedD M2 move away from each otheropenYoutube vid psychologicallyphysical addiction to nicotine dopamine productionIn lungs nicotine passes directly from epithelium into bloodstreamInteracts w CNS alpha4beta2nicotinic recsnatural recAchNicotine has higher receptivity for it agonistWhen 2 nicotine bind ion channel activatedOutcompete the recs for AChCA Na K pass thruact potdown axon to brain reward areadopamine releasedstimulate reward circuitshortlived good feelingsNicotine eliminated rapidlycraving for more dopamine downstream changes cause dependence for more dopamineRestining membrane pot largely due to K flux across membraneK high inside cellgrad90mM inside 3mM outsideIf channel openedK moves outsideUntil 45mM on both sidesbut DOESNT happen
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