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Q18 - Patch Clamp Analysis of a Cation Channel

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Plasma Membrane Structure & Transport

A researcher used a patch clamp technique to record the current of only a cation channel (single channel recording). The pipette contains 150 mM of KCl surrounded by a bath solution containing 150 mM of NaCl, and measures the channel current by clamping the voltage in different values. Current-Voltage curve (I-V curve) is shown in the following figure. deltaV = Vinterior - Vexterior. A negative current value (i.e., inward current) can reflect either the movement of positive ions (cations) into the cell or negative ions (anions) out of the cell. A positive current value (i.e., outward current) can reflect either the movement of positive ions (cations) out of the cell or negative ions (anions) into the cell.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. This channel is not selective, and both K+ and Na+ ions pass through this channel.
B. The Na+ current decreases with increasing voltage.
C. The K+ current increases with increasing voltage.
D. The resistance of the channel to negative voltages is less than positive voltages.
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Question reproduced from IBO 2018, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)