Pore inside cell membrane where ions can flow in and out of cell (proteins that span the cell membrane)
ion channel
Ions naturally attract
water
Because ions naturally attract water, it makes it unlikely they will just pass through ____________________________________ without help
phospholipid bilayer
Ions must ________________ travel through the holes created by ion channels
passively
Flow of ions depends on (1)
whether ion channel is open or not
Flow of ions depends on (2)
concentration gradient for the particular ion
Flow of ions depends on (3)
electrical gradient between inside and outside of cell
Ion channels change _____________________________ potential by conducting specific ions through the membrane in response to a variety of signals
membrane potential
Opening of ion channels involves a conformational change in _____________________________
(physical change or movement in the ion structure to open or close it)
protein structure
Ion channels are important is propagating an
action potential
4 types of ion channels
voltage gated
ligand gated (internal or external)
mechanically gated (stretch or pressure)
phosphorylation gated
Ion channel that change in membrane potential that causes the gate to open or close
voltage gated
Ion channel where molecule binds to another molecule
ligand gated
Ion channel that moves by membrane stretching or pressure put on membrane (ex: hair cells in ears)
mechanically gated
Ion channel where the phosphorogroup attaches to the protein
phosphorylation gated
Waters of _________________ partially determine size for selectivity
hydration
______________ ions (Na+) attract more water
smaller
Ions must shed __________________________ to go through small channels (energetically unfavorable unless charged amino acids lining channel are in specific arrangements)
waters of hydration
Once shed, __________ is smaller than ________ so can get closer to strongly negatively charged amino acids in the channel (carboxylic acid) and pick up compensatory energy
Na+; K+
Once water is shed, due to the selectivity filter, Na+ goes on through but
K+ stays out because it is too ___________
large
Pores with weaker amino acids (carbonyl oxygen atoms) select for ______
K+
Pores that are _____________ select for= sodium; Pores that are _____________ select for = potassium
stronger; weaker
The chloride selectivity filters are similar to K+ but the amino acids in channel are _____________________ charged to attract Cl- and repel K+/Na+
positively
We know what proteins and amino acids make up ion channels but we don't know exactly ______ they are put together (but we can guess based on properties of the proteins)
how
______________ form the pore and are important for selectivity
p loops
Positive (+) charges in S4 are important for __________________________ voltage sensing
transmembrane
The x-ray _____________________ method is used to measure structure of an ion channel
crystallographic
The ___________________ is used to measure function of an ion channel
patch clamp