Channels Flashcards
exam 2 material
what are the sources of ion channel diversity?
structure, selectivity, conductance, gating, and kinetics
what is x-ray crystallography used to visualize?
structure of ion channels such as the type of subunits present, pore region, and the presence of voltage sensors
what causes ion channels to open and close?
depolarization (inside becomes less negative) causes them to open and repolarization (inside becomes more negative) causes them to close
what are the different factors that influence ion channel structure?
trans-membrane spanning heteromeric/homomeric subunits, pore region, voltage sensor (positive or negative transmembrane loop that move with the membrane potential, opposite charge between voltage sensor and inside of the cell attract and close the pore and vice versa), auxiliary subunits modify how fast or slow a channel opens
what are the different factors that influence ion channel selectivity?
pore size (will the ion be able to travel through pore with its water shell attached) and the selectivity filter (component of each subunit that contains charged amino acid residues that interact with ions and strip their water shell)
what are the different factors that influence ion channel conductance?
whether the channel conducts ions or molecules, the direction of conductance, and modification of conductance by blockers, toxins, and drugs
ohmic vs inward rectifying vs outward rectifying channels
ohmic: symmetrical, ions can pass in either direction
inward rectifying: asymmetrical, ions flow in
outward rectifying: asymmetrical, ions flow out
what are the types of blockers, toxins and drugs that can modify conductance?
blockers: Mg+ blocks Ca2+ from passing through the NMDAR
toxins: tetrodotoxin blocks sodium channels
drugs: norvasc blocks calcium channels
heteromeric vs homomeric subunits
heteromeric: at least one different subunit
homomeric: 4 identical subunits
what are the three gating states of ion channels?
resting: closed but able to be activated
open: active, all or none
refractory: closed but not able to be activated
desensitization vs inactivation
desensitization: the state in which an ion channel becomes refractory due to prolonged ligand exposure
inactivation: channel cannot open because it needs to undergo a change
what are the different types of ion channels that have gating that is determined by a stimuli?
voltage gated, ligand gated, signal gated, thermosensitive, mechanosensitive
what are the different types of ion channels that’s gating is not determined by a stimuli?
open/leak channels, aquaporin, and connexon
what kind of stimuli influences the gating of voltage gated channels?
effects K+, Na+, Ca2+, Cl- channels, opposite attraction between channel and ion opens gate
what kind of stimuli influences the gating of ligand gated channels?
effects GABAR, AMPAR, and NMDAR, extracellular neurotransmitters bind to channel which allows them to open
what kind of stimuli influences the gating of signal gated channels?
effects cAMP, Ca2+, P, H+, and GTP, intracellular or extracellular neurotransmitters bind to the channel which allows them open, often responsive to changes in pH (changes in H+ concentration, high H+ = high pH)
what kind of stimuli influences the gating of thermosensitive channels?
transient receptor potential (TRP) channels sense pain and temperature, temperature rearranges the subunits forming the channel to allow it to open and send signal
what kind of stimuli influences the gating of mechanosensitive channels?
transient receptor potential (TRP) channels open in response to pressure
how do open/leak, aquaporin, and connexon channels work?
open/leak: make up certain K+, Na+, and Cl- channels in neurons, stay open most of the time
aquaporin: regulate how much water enters cell
connexon: quaternary protein structure that connects adjacent cells
what are the different types of K+ channels?
KV2.1 channels, KV4.2 channels, inward rectifier K+ channels, 2P K+ channels, and Ca2+ activated K+ channels
what are KV2.1 channels?
voltage gated, rapid opening, slow inactivation, gates excitation in dendrites (meaning there is a refractory period), role in repolarization
what are KV4.2 channels?
voltage gated, rapid inactivation, responsive to depolarization
what are inward rectifier K+ channels?
voltage gated but allow peak current through during hyperpolarization
what are 2P K+ channels?
2 subunits make up poor region, voltage-independent, signal gated (responsive to changes in pH, H+), leak channels allow H+ to escape to maintain membrane potential
