BIOCHEM 2EE3 Lecture Notes - Ionophore, Lipid Bilayer, Arrow Poison
17 Mar 2014
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Document Summary
Carrier ionophore: carry ions through lipid bilayer via diffusion. Channel-forming ionophore: channel spans entire bilayer through which ions can diffuse. Its shape makes it highly selective to k+. 108 ions per second, 104 times a greater rate than that of valinomycin. Functional groups at openings geometrically favour only k+ ions. Ligand-gated ion channels, such as nicotinic ach receptors, have 4 transmembrane helices and 5 pseudo-symmetric subunits. Antagonized by bungarotoxin, tubocuraine (arrow poison curare) and myorelaxants. Voltage gated ion channels: voltage sensors dictate opening/closing of channel. K+ channels: 4 identical subunits with 6 transmembrane segments. Na+ channels blocked by tertodotoxin and local anaesthetics. Ca2+ channels blocked by cardiovascular drugs and conotoxins. Tetrodotoxin: na+ channel blocker, named for being 4 toothed : poison characteristic of puffer sh in gonads, liver and intestines. Lipid soluble potent neurotoxin that binds voltage gated na+ channels. Most powerful animal venom released by poison dart frog.
