Lecture_8_Jan_22_

Lecture_8_Jan_22_ - Major topics to be discussed...

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1 Major topics to be discussed: Determination of ECG for a transported ion How is the transport direction of an ion determined? The origin of membrane potential How is the transport specificity of an ion channel achieved? How is the opening/closing of an ion channel controlled?
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2 Method 1: to determine the transport direction favored by the electrical and chemical driving forces separately electrical gradient: positive ions move toward the negative potential negative ions move toward the positive potential chemical gradient: always from high conc to low conc No math is required. One can only predict the direction but not the size of driving force One can only predict the direction but not the size of driving force
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3 i l M th d 1 What is the transport directions for Na + in a resting cell? electrical gradient: h i l di t simple case Method 1: chemical gradient: ECG di ti ECG direction: ECG driving force: ? Vm=-70 mV (Na + ) O = 145 mM (K + ) O = 5 mM (Na + ) i = 10 mM (K + ) i = 140 mM
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