Ch. 5 - Ion Channels Flashcards
three types of ion channels
voltage gated, ligand gated, mechanically gates
integral membrane proteins that span the cell membrane and form conduits for the ions to pass through the lipid bilayer
ion channels
ion channels can conduct blank ions per second
100
ion channels that are gated to changes in membrane potential
voltage
ion channels gated to chemical transmitters
ligand gated
ion channels gated to pressure or stretch
mechanically gated
resting channels are blank at rest
open
gated channels are blank at rest
closed
allow for continuous pathway for ions to move from inside to outside cell
ion channel
these have two gates that allow one ion in and out at a time and is active transport and is much slower than ion channels
ion pump
ion transported down electrochemical gradient causes energy to be blank
released
the energy released powers the blank to go against electrochemical gradient
pump
ion channel composed of 5 different subunits
hetero-oligomers
ion channel composed of 6 similar subunits
homo-oligomers
ion channel formed by repeating motifs and one chain
single polypeptide
ion channel can also contain auxiliary subunits in this type such as blank and blnak
gamma, beta
lipid bilayer consists of
phospholipids, proteins
ions surrounded by water is called blank and is blank than an ion alone
hydrated, larger
phospholipid tails have blank bonds which are blank
ester, hydrophobic
a hydrated blank ion has a larger diameter than a hydrated blank ion because it has a higher charge even though its smaller
sodium, potassium
blank ions are too large to get through blank channels
sodium, potassium
a sodium channel has a blank filter that has amino acids that strip blank from the hydrated sodium ion,
selectivity, water
three models for opening/closing of ion channel
localized conformational, generalized structural, blocking particle
gaba stands for
gamma, amino, butynic acid
drug that binds to gaba channels and keeps the channels open
valium
three states of voltage gated ion channels
closed resting, open, inactive
closed resting channels are blank
activatable
inactive voltage gated ion channels are blank
nonactivateable
regulatory in calcium channels
calmodulin
technique to record current through ion channels
patch clamp
patch clamp technique was created in what year
1976
this scientist formed vesicles under special conditions so the vesicles fused with the blank to form a blank
bilayer, artificial bilayer
artificial bilayer advantages
- can access ions inside the cell in the inner membrane such as the SR
- can study the membrane composition and ion channels
rate of flow of ion currents through ion channel
flux
direction of equilibrium constant of flux is determined by these two factors
- electrical potential difference on outside/inside cell membrane
- concentration gradient inside/outside
electrical potential difference and concentration gradient difference makes up blank difference
electrochemical potential
na+, k+, Ca2+ can pass through blank ion channels
cation selective
Na+ selective ion channel allows blank ions to pass through
Na+
cation selective ion channel that allow Na+, K+, and Ca2+ ions to pass through
Achr
flux of ions through ion channels is blank
passive
ion channel is either all the way blank or blank
open, closed
current is blank related to blank in the iv curve
linearly, voltage
ohms law
V = IR
volts, current (amps), resistance (ohms)
conductance formula
= 1/R
slope of the IV curve gives blank in these units
conductance, siemens
rate of current depends on the concentration of blank in the solution
ions
at a high ion concentration, a blank current can be reached making it constant
max
laws of binding of ions to special aa along the pore of an ion channel
electrodiffusion
ligand concentration at which current reaches half of the max current
dissociation constant
low dissociation constant means blank
strong bonding
transition of ion channels between closed and open
gating
linear iv curves conduct ions at a constant manner at all voltages in blank resistors/blank channels
simple, ohmic
iv curve that is non linear conducts ions more readily in one direction than the other
rectifier
comparing aa sequences in various species for blank regions
highly conserved (similar)
these channels are formed with parts derived from genes of different species
chimeric channles
site directed mutagenesis - uses a blank type ion channel and watch its function, then a mutation type of ion channel is made and its function is watched. if the functions are different, then the aa being studied plays a blank role in ion channel gating
important
each peak in the hydrophobicity plot represents the blank hydrophobicity of blank amino acids
average, 19
each peak in the hydrophobicity plot represents one piece of the blank in a cell membrane
ion channel
three superfamilies of ion channels
ligand gated (ach), gap junction, voltage gated
gap junction channel has blank subunits and blank domains
6, 4
ligand gated channels have blank subunits and blank domains
5, 4
voltage gated channels have blank motifs but is a blank polypeptide and has blank domains
4, single, 6
these channels bridge the cytoplasm of two cells at the electrical synapse
gap junction channel
there are blank related ion channels with blank regions
four, p
p region consists of a blank and blank
helix, loop
ligand gated ion channel is a blank oligomer
hetero
gap junction connexin channel is a blnak oligomer
homo
patch clamp records blank ion channels
one
scientist that made the artificial membrane bilayer
christopher miller
the p region of a bacterial potassium channel is aka the blank
selectivity filter
4 rings are formed by successive rings of blank atoms from blank amino acid residues per subunit
O, 5
fifth ring of O is formed by the OH side oxygen from blank
thrionine
in potassium ion channel, the ions have to either be in binding site blank and blank, or blank and blank because of blank
1,3 2,4 electrostatic attraction
2,4 bindings sites is the blank configuration
inner
1,3 binding sites is the blank configuration
outer
high energetic cost for a potassium to enter lipid bilayer is minimized by two parts:
- inner chamber
2. four helices provide dipole whose neg charge points to inner chamber
two identical subunits each forming a selective Cl pore
dimers
abnormal prolonged muscle contraction
myotonia
to pump Cl to outside cell against conc gradient, blank are moved down concentration into the cell to power that pump
H+
potassium channel is a blank channel
parallel
chlorine channel is a blank channel
antiparallel