Neuronal Membrane Channels
Neuronal Membrane Channels NSCI 3310
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This 3 page Class Notes was uploaded by Emma Notetaker on Tuesday September 29, 2015. The Class Notes belongs to NSCI 3310 at Tulane University taught by Jeffrey Tasker in Summer 2015. Since its upload, it has received 31 views. For similar materials see Cellular Neuroscience in Neuroscience at Tulane University.
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Date Created: 09/29/15
Neuronal Membrane and Ion Channels 09/02/2015 ▯ ionic environments aqueous: o H2O – polar o positive and negative poles salts: NaCl, KCl, CaCl2 o dissolve in h2o o form ions o Na+, K+, Ca@+, Cl- o same for both intra and extracellular enviironments ▯ phospholipid bilayer two layers/sheets of amphipathic [hospholipids o polar/watter attracting head o non-polar, water-repelling tail impermeable to charged particles o outer leaflet is POLAR – prevents ions from crossing o energy required for ions to cross plasma membrane ▯ membrane components: membrane proteins – facilitate ion and info flow acorrs membrane o integral – amphipathic and span intra to extra cellularly ion channels ion pumps o peripheral: located to one side of the membrane G proteins cholesterol – determines membrane fluidity carbohydrates: how cells interact with other cells and proteins o glycolipids – interact with matrix and other cells o glycoproteins – protein-protein interaction ▯ membrane protein structure: primary – amino acid chain (linked by peptide bonds) o amino acids classified as hydrophobic (will stay in membrane) or hydrophilic (organize on end of membrane to touch water) o classified by R group secondary – alpha helix and B sheet tertiary – protein folding o complete protein (ONE amino acid chain) quaternary – association of MULTIPLE tertiary structures o THESE are the actual membrane proteins o VERY rarely will an actual membrane proteins only one strand ▯ membrane protein function: ion channels (ionotropic receptors) – pores, gated and selective transporters – ion pumps and carriers, ATP-dependent metabotropic receptors – trigger intracellular reactions (2 nd messenger cascades) cell interactions – junctions, adhesion, migration and maturation ▯ ion channel: ion selective o ion filter o Na+, K+, CA2+, Cl- o possible mechanisms that determine selectivity: charge size water (what water is attaching to) gated o not open all the time – open and close localized general conformational change (changes shape to close pores ball and chain model – protein blocks gate o can have multiple gates per channel Types: divided based on how the gates are opened o leak – open all the time flux ions at very slow rate (like a faucet) o ligand-gated: dependent on neurotransmitters (ligands) ionotropic receptor nd o 2 messenger-gated dependent on phosphorylation (add phosphate group to channel, causes it to open) dependent on G protein o voltage-gated: dependent on membrane potential voltage sensors of the cell o mechanically gated sensitive to stretch of membrane often in peripheral nervous system (touch receptors) ion pumps and transporters proteins use ATP in order to move ions o expend energy – active process Na+/K+ pump (video on slide) o ATPase (because it uses ATP) – P group binds to receptor on pump o pumped 3 Na OUT, 2 K IN (per ATP) o maintains membrane potential – creates concentration gradient o net charge inside the cell is NEGATIVE o when K binds, dephosphorylated pump ▯ ▯
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