Ion channels and membrane currents Flashcards
Why don’t ions pass through the lipid membrane?
Diffusion of polar and charged molecules is not thermodynamically favourable since charged molecule is more attracted to polar head of membrane.
Example of voltage-gated ion channel
Voltage-gated sodium channel -> opens on depolarisation
Example of leak-operated channel
Tandem pore domain potassium channels -> constitutively open/ possess high basil activation -> set negative membrane potential
Example of ligand-gated channel
Nicotinic Ach receptor - pentamer 2 binding sites for Ach
Patch clamping means
isolate a patch of membrane electrically from the external solution and to record current flowing into the patch
Different modes of patch clamping
- Cell-attached patch
- Inside-out patch
- Whole cell recording or whole cell patch
- Outside-out patch
- Perforated patch
- Loose patch
Open probability (P)
The probability of a gate being open
What is an IV diagram?
Voltage current diagram
-> mV vs pA
How can trans-membrane voltage and ligand concentration affect P?
Is the channel voltage or ligand gated?
How would you use patch clamping to determine the entire population of channels present in a nerve cell membrane?
a single voltage-clamp amplifier sums the whole-cell currents from multiple cells at once, each sealed to a separate aperture in a planar substrate well
How would you use patch clamping to determine the open probability of a single glutamate-gated ion channel in the presence of different concentrations of an agonist
think
How would you use patch clamping to determine the voltage-dependence of the current flow through a sodium channel in an axon membrane
think
How would you use patch clamping to determine the open probability of an ion channel gated by the binding of an intracellular ligand and its dependence on ligand concentration
think
A linear IV line means
Not voltage-dependent
