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Lecture 8 (Sept 11) - Exam 1 is one week from today Ne xt...

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Exam 1 is one week from today Next Friday, September 18 Thetest will cover lectures 1-10 (this means through next Wed) Exam Review next wednesday! Here (SC4327), 4-6pm Question-and-Answer Session Only!!! Come prepared with your questions
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Lecture8: Electrochemical gradients & signaling Electrochemical gradients and membranepotential Voltage- and ligand-gated ion channels Structureand functional properties of ion channels Ionic basis of the action potential Saltatory conductance in nerve cells Structureand function of theneuromuscular junction Themechanism 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 (insidenegative). Sincethe plasma membraneis ~3.5 nm thick, this equates to a voltage gradient of 200,000 V/cm! For comparison, high voltage electrical wires havea gradient of 200,000 V per kilometer length. A 100,000-fold difference.
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Differential Distribution of Ions Across thePlasma Membrane ATPase pumps maintain ionic gradients across plasma membrane Electrochemical Gradients (potential energy source) VoltageRecording (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 thereis no potential difference
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