Lecture 3 - Lecture 3 Membrane Potential brain and muscle function are electrochemical phenomena Bioelectricity voltages in cells are generally

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Lecture 3 Membrane Potential brain and muscle function are electrochemical phenomena Bioelectricity voltages in cells are generally less than 100 mV (millivolts) currents are in the range of nA (nanoamps)
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Ion Selectivity of K + Channels K + selected over Na + by ratio of 1:10,000 Ion radiuses: K + 1.33 Å and Na + 0.95 Å High throughput of K + (10 8 / second) How is high selectivity achieved without compromising the high throughput of K ions?
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K Channel Structure tetramer
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hydration shell
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Selectivity Filter
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carbonyl oxygen atoms
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K + ions move in and out of the channel without encountering any large energy barriers because the four-fold symmetry of the channel mimics the normal inner hydration shell of the ion Rings of four carbonyl oxygen atoms above and below the ion within the pore substitute for similar rings within the hydration shell Ions move through the pore due to the constant flipping between two stable channel states Permeation
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Ion Selectivity of K + Channels K + selected over Na + by ratio of 1:10,000 Ion radiuses: K + 1.33 Å and Na + 0.95 Å High throughput of K + (10 8 / second) How is high selectivity achieved without compromising the high throughput of K ions?
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Ions move through solution by diffusion water molecules, 75% of total body weight and 99% total number of molecules pure water, a poor conductor of electricity
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Because of its polar nature water is an excellent solvent for salts, acids and bases salts, acids, bases, dissociate into ions in water Na + and Cl - NaCl table salt uncharged, cannot carry a current
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ionic bonds
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This note was uploaded on 02/15/2011 for the course BIO 328 taught by Professor Cabot during the Fall '07 term at SUNY Stony Brook.

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Lecture 3 - Lecture 3 Membrane Potential brain and muscle function are electrochemical phenomena Bioelectricity voltages in cells are generally

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