lecture_10_12 - III.C.5 Diversity of ion channels Ion...

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Ion channels are proteins and properties of proteins are directly related to function Can you list some of these properties? III.C.5. Diversity of ion channels. III.C.6. Some techniques to study channels. Some techniques used to study channels 1) Channel blockers - examples TTX and TEA TTX - selective blocker of VG-Na channels 1)_______________________________________ 2)_______________________________________ ) Voltage affecting tertiary structure (e.g., voltage gating) other properties that affect structure (e.g., pH, temperature, charge, phosphorylation, etc.) ion gating changing protein structure. For example Ca ++ gated otassium channel natural toxin in bladder of puffer fish and used by some spiders in venom. Also used in voodoo to make “zombies” TEA - selective blocker of VG-K channels Found in some spiders venom 2) Vary ionic concentrations -see computer exercises 3)_______________________________________ 4)_______________________________________ ) potassium channel Other chemical gating. For example neurotransmitter which we will talk about later Dynamics of gating. For example, how slowly or quickly does configuration of the molecule occur. 3) Voltage Clamp - See computer exercises; also we will go over in later lectures 4) Intracellular, extracellular and patch recording from cells - see pg 118- 122. 5)_______________________________________ reconfiguration of the molecule occur. III.D.1.a Myelin's effects on membrane resistance III.D.1.b. Myelin's effects on membrane capacitance Membrane Resistance (1) The cell membrane under the myelin has very few channels of any sort. (2) The myelin is so tightly wrapped around the cell membrane that ions cannot leak into the extracellular fluid. Do you think that the resistance of the cell membrane in the areas wrapped by the myelin sheath will be high? Answer: Yes Membrane Capacitance The sheath is also composed of a fatty glial cell, and therefore, ions cannot travel through the lipid sheath. How does this sheath effect the 3 roperties of a capacitor? properties of a capacitor? (1) Charge can collect on it (surface area): no effect (2) Non-conductive boundary: negligible effect since lipid bilayer is already almost completely impermeable to ions. (3) Ions can interact on either side (thickness): ions can interact MUCH less, thereby, decreasing capacitance So increasing thickness of the fatty barrier across the cell membrane will decrease the membrane capacitance because it will be difficult for gy p ions inside the cell to interact with ions on the on their side of the myelin.
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This note was uploaded on 11/22/2009 for the course NPB 100 taught by Professor Chapman during the Fall '08 term at UC Davis.

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lecture_10_12 - III.C.5 Diversity of ion channels Ion...

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