ion channels

Question 1

What is the function of ion channels?

Answer 1

To move ions and polar molecules across a selective transporter

Question 2

Describe when ion channels are open/closed for K and Cl and the net loss/gain

Answer 2

open at rest for K and Cl
small net loss of K
small net gain Cl

Question 3

Describe the chemical distribution of ions

Answer 3

Na + Cl + Ca pulled in

K pushed out

Question 4

Describe the electrical distribution of ions

Answer 4

Na + Ca + K pulled in

Cl- pushed out

Question 5

Approx ionic concentrations for internal

Answer 5

K = 140-150
Na- 5-15
Cl= 4-10
Ca= <0.0002

Question 6

Approx ionic concentrations for ECF

Answer 6

K =3-5
Na = 135-145
Cl = 95-110
Ca -1.8-2.5

Question 7

Describe Ex

Answer 7

equilibrium potential = voltage where elec + chem gradients are balanced
no net movement and can be calculated using nernst equation

Question 8

describe the mechanism of action of K channels

Answer 8

always open

Question 9

describe the mechanism of action of voltage gates channels

Answer 9

open/close in response to change in membrane potential

Question 10

describe the mechanism of action of ligand gated channels

Answer 10

open/close in response to to specific EC ntsmttr

Question 11

describe the mechanism of action of signal gated channels

Answer 11

open/close in response to specific molecule

Question 12

what is current

Answer 12

movement of charge over time

Question 13

Describe the subunits and transmembrane domains of ligand gated channels

Answer 13

5 subs, 4 transdomains
2nd tdom (M2) is the segment that lines the central pore of channel

Question 14

describe the superfamily of ligand gated channels

Answer 14

cys-loop family has conserved cysteine amino acids n N terminal domain
Gaba + glycine + nAChR + serotonin receptors are closely related
glutamate is less closely related

Question 15

Describe the inflections on the graphs for activation of ligand binding

Answer 15

pos inward current = down

pos outward current = up

Question 16

ionotropic glutamate subunit structure

Answer 16

tetramer

nmda receptors are ca2+ permeable w/long open times

Question 17

Voltage gated channels act/de/inactivation

Answer 17

activation = depolarisation 
deact = hyperpolarisation 
inact = non-conducting because of conformational change

Question 18

S4 domain….. describe her please

Answer 18

it’s positive, and physically displaced when channels are gated
when open they are displaced towards EC side