L7 - ions and electrochemical equilibria at the membrane Flashcards

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1
Q

define patch clamping

A

measurement of electrical potential by placing electrode on membrane

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2
Q

describe electrode of patch clamping technique

A

thin capillary tube filled with conducting solution and wire

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3
Q

explain process of measuring intracellular/extracellular potential

A
  1. electrode placed in electrode holders which are mounted in micromanipulators
  2. place electrode inside / outside cell
  3. connect to volt meter
  4. compare to a reference point further away from cell (0V)
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4
Q

explain process of patch clamping

A
  1. electrode placed in electrode holders which are mounted in micromanipulators
  2. tip of electrode broken and flamed in bunsen burner making it smooth
  3. end brought in contact with membrane and suction applied
  4. membrane is slightly sucked into the electrode
  5. allows measurement of potential in a ‘patch’ of the membrane e.g where channels are
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5
Q

what can patch clamping show you

A

how potential changes with the opening/closing of a channel within a patch in the membrane

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6
Q

explain the setup of resting membrane potential

A
  1. ATPase pump pumps 3Na out and 2K in
  2. K+ channels are open so some flow out following conc gradient
  3. therefore the inside is relatively more -ve
  4. equilibrium created with no net flow of current
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7
Q

how is this membrane potential intensified?

A
  1. Cl- tries to follow the K+ but cannot pass through the channel so it accumulates on the inner membrane
  2. K+ accumulates on the outer membrane surface (attracted to the Cl-) creating a ‘shell’
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8
Q

explain the concept of the nernst equation

A
  1. if conc gradient (of ion) is known, it can be used to calculate the membrane voltage using the nernst equation
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9
Q

what is the nernst equation

A

for positive ions:
E = 58 x log conc out / conc in

E = ebm potential
58 in mV

for -ve ions just swap conc in / conc out

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