Ion Channels And Disease

Question 1

How can we measure the current that flows through an open ion channel?

Answer 1

Ohms law

Question 2

Equation in Ohms law:

Answer 2

V = IR

Question 3

Ohms law: V

Answer 3

Voltage in volts (typically mV)

Question 4

Ohms law: I

Answer 4

Current in amperes (typically pA)

Question 5

Ohms law: R

Answer 5

Resistance in ohms (typically MΩ)

Question 6

What is used to measure the ionic currents involved in cellular functions?

Answer 6

Electrophysiological recording

Question 7

What’s a patch clamp?

Answer 7

Direct recording of ionic currents from cell surface ion channels

Question 8

What’s included in a patch clamp?

Answer 8

Amplifier -> digitiser -> computer

Question 9

What’s a patch clamp recording used for?

Answer 9

Voltage-clamp and current recordings

Question 10

What are planar lipid bilayer techniques?

Answer 10

Direct recording of ionic currents from intracellular ion channels

Question 11

What’s included in planar lipid bilayer?

Answer 11

Amplifier -> Digitiser -> Computer

Question 12

What’s a planar lipid bilayer used for?

Answer 12

Voltage-clamp recordings

Intracellular ion channels

Question 13

What information can we obtain from single channel recordings?

Answer 13

What opens the channel

Single channel conductance

What ions flow through the channel (ion selectivity)

Inhibitors of the channel

Question 14

What opens the channel?

Answer 14

Voltage

Ligands

Stretch

Light

Question 15

How does voltage open the channel?

Answer 15

Changing membrane voltage in depolarising or hyperpolarisation direction

Question 16

How do ligands open the channel?

Answer 16

Neurotransmitter binds and activates from outside cell

OR

2nd messenger binds at cytosolic surface and activates channel

Question 17

What stretch opens the channel?

Answer 17

Mechanosensitive channels

Question 18

What channels use light for activation?

Answer 18

Channelrhodopsin

Question 19

What doses single channel conductance mean?

Answer 19

How good a channel is at letting current through

Question 20

What are unitary NA+ currents like?

Answer 20

Fast activating and deactivating current

Question 21

What are unitary K+ currents like?

Answer 21

Slow activation

Doesn’t desensitise

Question 22

What is whole cell current equal to?

Answer 22

Products of number of channels, unitary current and probability of channel opening

Question 23

How do you determine which ions flow through the channel?

Answer 23

Clamp voltage across membrane patch + measure I open channel current

Construct current voltage relationship

Question 24

What’s Erev?

Answer 24

Reversal potential

Question 25

What should Erev correspond to?

Answer 25

Equilibrium potential of one of the ions in solution

Question 26

What inhibitor can inhibit Na+ channels?

Answer 26

Tetrodotoxin

Question 27

What inhibitor can inhibit K+ channels?

Answer 27

Tetraethylammonium

Question 28

What is influx of Ca+ important for?

Answer 28

Fertilisation Proliferation Secretion Heart beat Muscle contraction

Question 29

What can happen if Ca2+ balance isn’t regulated?

Answer 29

Apoptosis Ischemia Excitotoxicity Cardiac arrhythmmias Malignant hyperthermia