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1. Patch clamp recording of a single ion channel yields the following results Holding Potential Measured Current (mV)(pA) 0.0 -100 -50 +2.0 +3.0 ta +50 +100 A) Draw a graph of the current (on the vertical axis)-voltage relation for this channel. B) What isthe electrical resistance ohms of this channel? keep in mind mv= 103 volts, pA 1012 amperes, and an ohm is a derived unit that is equivalent to a volt/ampere, i.e. a VIA) C) What is the conductance of this channel in siemens (S)? (keep in mind 1 S-1/ohm) D) What would be the equivalent conductance of 1,000 of these channels opened at the same time?

Answer 1

Given Holding potential (mv) Measured current (PA) -100 -1.0 -50 0.0 0 + 1.0 + 50 + 2.0 + 100 + 3.0 A) The current (on the vertical axis) - voltage relation \r\n resistance = 1/slope of I.V graph = [50 - (-50)] times 10^-3/[2.0 - 0] times 10^- 12[using 2^nd & 4^th reading] = 100 times 10^-3/2 times 10^-12 = 5 times 10^10 Ohm C) conductance = 1/Resistance Rightarrow 1/5 times 10^10 Rightarrow 2 times 10^-11 s D) equivalent Resistance of 1000 channels opend at some Time (This is parallel) = Resistance of on channel/1000 = 5 times 10^10/1000 = 5 times 10^7 Ohm Therefore equivalent conductance of 1000 channels opend at same Time = 1/5 times 10^7 Rightarrow 2 times 10^-8 s