Membrane Transport & Ion Channels: Lectures 3-7 Flashcards
what is the resting membrane potential ?
-50 mV
which are the ions outside the cell?
sodium, Chloride, calcium
what is too much/ little potassium called?
Hyperkalaemia = High
Hypokalaemia = Low
What is the normal range of potassium mmol/l?
3.5-5.3 mmol/l
What is tetrodotoxin (TTX) ?
sodium channel blocker
What is Charybdotoxin (CTX)?
Potassium channel blocker
What is agatoxin and what is the effect?
Calcium channel blocker- voltage sensor.
Blocking voltage sensor means affects gating- opening/closing of voltage gated channels
How are ion channels are selective and specialised?
Substrate selectivity- selective for specific ions
Specialised with gating- open/close is controlled
2 ways to investigate ion channel struture?
Looking at amino acid sequence to make prediction about structure
Experimentally- x ray crystallography (standard) or electron microscopy
How does x-ray crytallography work?
Crsytallise the protein and when x-rays hit it, the light difracts and forms diffraction pattern which show electron density. Using unique properties of amino acids, can predict which amino acids are where and create atomic model.
Why are ion channels difficult to crystallise? (6)
transmembrane
large proteins- high molecular weight
multiple conformations
multiple subunits
dynamic- they open and close.
not very soluble
What is cryo-EM?
cryogenic electron microscopy. Plunge freeze the purified protein sample to view the structure. Doesn’t need the protein to be in a static fixed state like in x-ray crystallography. So when hit with electrons, it shows the proteins in different states
What is alphafold?
using protein structure databanks to predict protein structures using AI
What is the ion channel structure like?
Made up of alpha subunits. Potassium channel is tetramers so 4 alpha subunits but also 2 beta.
