Ion Channels And Disease Flashcards
How can we measure the current that flows through an open ion channel?
Ohms law
Equation in Ohms law:
V = IR
Ohms law: V
Voltage in volts (typically mV)
Ohms law: I
Current in amperes (typically pA)
Ohms law: R
Resistance in ohms (typically MΩ)
What is used to measure the ionic currents involved in cellular functions?
Electrophysiological recording
What’s a patch clamp?
Direct recording of ionic currents from cell surface ion channels
What’s included in a patch clamp?
Amplifier -> digitiser -> computer
What’s a patch clamp recording used for?
Voltage-clamp and current recordings
What are planar lipid bilayer techniques?
Direct recording of ionic currents from intracellular ion channels
What’s included in planar lipid bilayer?
Amplifier -> Digitiser -> Computer
What’s a planar lipid bilayer used for?
Voltage-clamp recordings
Intracellular ion channels
What information can we obtain from single channel recordings?
What opens the channel
Single channel conductance
What ions flow through the channel (ion selectivity)
Inhibitors of the channel
What opens the channel?
Voltage
Ligands
Stretch
Light
How does voltage open the channel?
Changing membrane voltage in depolarising or hyperpolarisation direction
How do ligands open the channel?
Neurotransmitter binds and activates from outside cell
OR
2nd messenger binds at cytosolic surface and activates channel
What stretch opens the channel?
Mechanosensitive channels
What channels use light for activation?
Channelrhodopsin
What doses single channel conductance mean?
How good a channel is at letting current through
What are unitary NA+ currents like?
Fast activating and deactivating current
What are unitary K+ currents like?
Slow activation
Doesn’t desensitise
What is whole cell current equal to?
Products of number of channels, unitary current and probability of channel opening
How do you determine which ions flow through the channel?
Clamp voltage across membrane patch + measure I open channel current
Construct current voltage relationship
What’s Erev?
Reversal potential
What should Erev correspond to?
Equilibrium potential of one of the ions in solution
What inhibitor can inhibit Na+ channels?
Tetrodotoxin
What inhibitor can inhibit K+ channels?
Tetraethylammonium
What is influx of Ca+ important for?
Fertilisation
Proliferation
Secretion
Heart beat
Muscle contraction
What can happen if Ca2+ balance isn’t regulated?
Apoptosis
Ischemia
Excitotoxicity
Cardiac arrhythmmias
Malignant hyperthermia
