Lecture 8 (Sept 14)

Lecture 8 (Sept 14) - Biological Sciences 110A:...

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Electrochemical gradients and membrane potential Voltage- and ligand-gated ion channels Structure and functional properties of ion channels Ionic basis of the action potential Saltatory conductance in nerve cells Structure and function of the neuromuscular junction The mechanism of synaptic transmission Biological Sciences 110A: Introduction to Biology Kendal Broadie Reading in Chapter 4 (150-170) Karp
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K m 0.6 mM; [Na] ~12 mM (Na+ binds with high affinity) K m 0.2 mM; [K] ~4 mM (K + binds with high affinity) Review : Na+/K+ ATPase establishes electrochemical gradients Fig. 4.45 Karp
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All cells maintain electrical gradients across the plasma membrane A typical cell maintains an electrical potential of ~70 mV (inside negative). Since the plasma membrane is ~3.5 nm thick, this equates to a voltage gradient of 200,000 V/cm! For comparison, high voltage electrical wires have a gradient of 200,000 V per kilometer length. A 100,000-fold difference.
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Differential Distribution of Ions Across the Plasma Membrane ATPase pumps maintain ionic gradients across plasma membrane Electrochemical Gradients (potential energy source) Voltage Recording (potential difference) Voltage-Gated Ion Channels : - Ion selective - Voltage- dependent pore
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Artificial cells with ionic gradients comparable to normal cells without ionic flow there is no potential difference if the membrane is selective ly permeable to Na+, these ions flow down their [ ] gradient until the electrical potential balances the chemical potential. The charge
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Lecture 8 (Sept 14) - Biological Sciences 110A:...

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