Ion Channel Structure/properties Flashcards
Which method studies ion flux in ion channels
Patch clamp technique
Why are eggs from frogs used to study ion channels
Large and easily manipulated to express ion channels
What is mutation to study ion channels called
Directed mutagenesis
Which animal was the shaker k channel expressed in first
Drosophila
What 3 gates are there on ion channels
Voltage
Ligand binding
Mechanical
What does the chemical tetrodotoxin do
Interacts with gate of ion channel and prevents na passage
Which animals have tetrodotoxin which blocks na passage
Puffer fish
Which chemical blocks k ion channels
Tetra ethyl ammonium
What does the aa sequence of ion channels predict
Which areas are EC and ic depending on hydrophobicity etc and predicts secondary a helix or beta sheet
What makes up a single alpha subunit in K channels
6 x transmembrane alpha helixes (s1-s6)
How many alpha subunits are there in a k channel
4- k channel is a tetramer
Where is the pore region located in every a subunit of k channel
Between s5 and s6 alpha helix
Which conserved sequence was found on s4 alpha helix later found as voltage sensitive
6 arginine + residues
When voltage changes around channel what happens
Sensed by s4 conserved voltage sensor
S4 region pulled into membrane and pulls on the s4-s5 link
This pulling of s4 leads to pore opening in all 4 alpha subunits at s5/6
What conserved sequence is in the pore region for selectivity
Tvgyg (5aa)
When k is dissolved in water at both sides of ion channel. What surrounds it
8 h20 molecules (solvation shell)
What allows stability for k to enter pore region
The c terminal of alpha subunits are negative vs positive k
What is the region with the tvgyg sequence called in pore region
Selectivity filter
What happens in the selectivity filter
Solvation shell stripped and replaced with o2 until k leaves ion channel
How many bs are there for k in selectivity filter
4 - always 1 bound and pushes another through
Why can’t ca enter k channels
Too big
Na isn’t too big. Why can’t it move through k ion channel
Energetically not possible to strip its solvation shell and replace with o2 so can’t move in selectivity filter
Which part of alpha subunit is important for channel inactivation
The amino n terminal
What happens in inactivation (h gate)
Amino n terminal blocks the s5-6 pore region
Are there other inactivation processes other than amino blocking pore region (h gate)
Yes Eg phosphorylation
What speed is standardised on ecg paper
25mm/s
Height (electrical activity) = 1mm=1mv
What is the pr interval
From start of atrial depolarisation to onset of ventricular depolarisation (how long it takes from atria to ventricles)
What does qrs represent
Electrical movement through purkinje fibres and bundle of his
What causes wide qrs
Issue with conducting system through the purkinje fibres
What is qt interval
Amount of time it takes ventricles to dep and repolarise fully (end of t wave)
What is long qt syndrome
Delayed repolarisation of ventricles due to abnormal ion flow in channels
Long ap which can cause ca channels to reopen and cause extra ap/arrhythmia
What is your risk of early ap called in long qt syndrome
Early after depolarisation
Causes ventricular tachycardia
How do you fix long qt syndrome if it causes ventricular tachycardia/arrhythmia
Implantable cardiac defibrillator icd
Sends electric shock which restores normal heart beat
