Ion channels

Question 1

Selective permeability is?

Answer 1

preference over one type of ion over another

Question 2

Electrochemical gradient is?

Answer 2

the active transport of ions across the cell membrane causes an electrical gradient to build up across this membrane.

Question 3

permeant ion can either be?

Answer 3

Highly selective :Sodium, potassium, calcium, chloride
Non-selective

Question 4

3 different types of gating mechanisms?

Answer 4

voltage, Ligand, Mechanical

Question 5

Cyclic nucleotide gated channel:

Answer 5

Activated by the binding of cGMP or cAMP.
Transduce changes in intracellular concentrations of cyclic nucleotides into changes of membrane potential & Ca2+ concentration.

Question 6

Ca2+ activated K+ channel:

Answer 6

On activation by low concentrations of Ca2+, they open, which results in hyperpolarization of the membrane potential and changes in cellular excitability.

Question 7

Voltage-gated channels examples include:

Answer 7

Na+ / Ca2+/ K+/ Cl-

Question 8

Voltage-gated sodium channels: Family of 9 genes termed ?

Answer 8

SCNA1-9

Question 9

Voltage Gated ion channel structure

Answer 9

4 domains, with 6 transmembrane regions
5 proteins
(Segment 4 has lots of positively charged amino acids- voltage sensor )

Question 10

Inactivation:

Answer 10

process by which an open channel enters a stable nonconducting conformation after a depolarising change in membrane potential

Question 11

Voltage sensors are down at the bottom because?

Answer 11

membrane potential is negative

Question 12

what causes the 4th segment (voltage sensor) to move up?

Answer 12

when amino acids get repelled because of the membrane potential getting less negative

Question 13

how does voltage gated ion channels work? e.g sodium

Answer 13

Membrane potential starts to creep up
Depolarisation–> voltage sensors move up the membrane
Sodium ions move into the cell–> action potential
Ion channels inactivate because blocking portal gets in the way
Potassium channels open & brings the membrane potential back down

Question 14

Voltage gated ion channels inactivate because ?

Answer 14

bit of protein blocks / gets in the way so no ions can move out

Question 15

Channel activation / opening

Answer 15

• the process where the channel pore is open to allow ion diffusion produced by the introduction of the activation stimuli.

Question 16

Gating

Answer 16

• the process whereby a channel becomes open

Question 17

Inactivation

Answer 17

• the process whereby a channel conducts little ion flow due to the obstruction of the pore by either blockage due to an intracellular part of the channel or due to collapse of the outer part of the channel.

Question 18

Closed

Answer 18

• where the channel is not allowing ion flow due to the activation mechanism not being in place rather than because inactivation has occurred.