Ion Channels Flashcards
3 essential functions of ion channels
Secretion and absorption of fluids
Regulate membrane potentials for nerve and muscle cells
Ca2+ influx into cytoplasm for muscle contraction
Simple ion channel (K+) structure
2 subunits
Transmembrane helicase structures form a P-Loop
More tightly packed transmembrane domains on cytoplasmic side, forming a gate
When ions flow, domains move, causing channel to open
Factors that control simple ion channel gate
Mechanical stress, ligand binding, membrane potential
Main functions of voltage gated ion channels
Na+ and K+ create action potentials
Ca2+ can be transported into cytoplasm where 2nd messenger elicits cellular response
Structure of voltage gated ion channels
4 subunit
Voltage sensing domain formed by S1 and S4 helices
Large polypeptides extend into cytoplasm
Plugging mechanism blocks pore to stop ions entering
Transient receptor potential channels
Sense chemical and physical stimuli
Detects spicy food and temperature of food
Structural features of all ion channels
Transmembrane protein
2 or more ⍺ helices that cross lipid bilayer
2-6 subunits surrounding a pore
How are ion channels classified
Gating mechanism (voltage or ligand)
Ion selectivity (defined by size of filter and amino acids lining the pore)
Cyclic nucleotide gated channel structure
6 TM domains
4 subunits
S5 and S6 line central pore
P-loop controlling filter
To open ligand must bind to 3/4 sites
When Ca2+ binds to N terminal associated with calmodulin - channel closes
Nicotinic receptor family structure
4 TM domains
5 Subunits
Examples of nicotinic receptors
nACh receptor
GABAa Receptor
Structure of Glutamate family receptors
3 TM domains
4 subunits
Examples of glutamate receptors
AMPARs
NMDARs
ATP P2X receptor family structure
2 TM domains
3 subunits
ATP binding site in extracellular domain
