Ion Channels Flashcards
What causes changes in membrane potentials?
The movement of ions through the plasma membrane
Can ions pass through plasma membrane?
Not by itself, it needs an ion channel.
What is the difference between ion channels and pumps/active transporters?
Ion channels allow diffusion down electrochemical gradient (no energy); Pumps move ions against electrochemical gradient (energy)
What biological processes depend on ion channels
- neuronal signaling/sensory transduction
- muscle contraction
- regulation of salt/water balance
- fertilization
- cell proliferation
- cell death
- hormone secretion
What are channelopathies?
They describe severe and muscle diseases due to defects in ion channels
What is Long QT Syndrome?
A rare congenital heart disease, caused by a prolonged QT interval on electrocardiogram because of delayed repolarization after action potential
What causes Long QT Syndrome?
Mutations in voltage-gated K channels
What are important ion channel features?
- found in all excitable cells
- different subunits arrangements
- more or less ion selective
- regulated or not
What is nicotinic acetylcholine receptor?
It is an pentameric ion channel with 4 membrane-spanning regions that binds acetylcholine
What is ion selectivity?
Whether an ion channel is specific for an ion, or lets any ions with a specific charge through
What are the modes of activation?
- Channels are activated by physical changes in the cell membrane (ie. voltage gated sodium channel and stretch-activated calcium channel)
- Channels activated by ligands (ie. nicotinic acetylcholine receptor and cGMP-activated sodium channel)
How do voltage-gated ion channels work?
They undergo conformation changes in response to changes in membrane potential
How many domains does the voltage-gated sodium channel have? How many membrane-segments does each domain have?
4 domains; 6 membrane-spanning segments
What do ligand-activated ion channels do?
They transduce a chemical signal into an electrical signal; activated by neurotransmitters
What is glutamate?
It is a neurotransmitter that can bind to multiple receptors (ionotropic or metabotropic)
What is ionotropic?
ion channel
Metabotropic?
G-protein coupled receptors that activate or inhibit other channels via signaling
What are the 3 ionotropic glutamate receptors?
NMDA, AMPA, Kainate
(NMDA permeable to Na, K AND Ca)
How do you measure single channel currents?
Electrophysiological recording methods
What are the electrophysical recording methods?
- Extracellular recording (looks at firing behavior of neurons)
- Intracellular recording (looks at membrane potential)
- patch-clamp recording (looks at single ion channel current)
Who developed patch-clamp current?
Erwin Neher and Bert Sakmann
Why is it important to know the structure of ion channels?
- To understand how ion channels work and how they are regulated
- To develop drugs to manipulate ion channels
What are important techniques that reveal ion channel structural information?
- Biochemical and molecular
- Biophysical methods
- Computational Methods
What are the different structures that can form pores?
- Hetero-oligomer
- homo-oligomer
- Single polypeptide that spans the membrane several times
