Bio365-34-042110 - Phototransduction -30 mV -70 mV...

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Phototransduction
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-30 mV -70 mV
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cGMP 5’GMP Ligand that binds to Na+ channels Does NOT bind to Na+ channels Intracellular Disk
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Light One rhodopsin molecule absorbs one photon 500 transducin molecules are excited, each activate PDE 100,000 cyclic GMP molecules are hydrolyzed One million Na ions per second are prevented from entering the cell 500 phosphodiesterase molecules are excited and become active 250 Na channels close +
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Rhodopsin + light Activated Rhodopsin Rhodopsin kinase Activated Rhodopsin (phosphorylated) P Arrestin Activated Rhodopsin (phosphorylated) P arrestin Action of Rhodopsin is Terminated after light flash Process takes a bit of time (few hundred milliseconds) Specialized system to stop amplification -rhodopsin kinase phosphoylates active rhodopsin -arrestin binds to phosphorylated rhodopsin and prevents it from activating more G-protein
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All-trans retinal Active site on opsin is exposed The active site activates transducin and changes rod membrane potential Active site Metabolic energy
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Bio365-34-042110 - Phototransduction -30 mV -70 mV...

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