Ion Channels and Disease

Question 1

What methods are used to measure current?

Answer 1

Patch clamp - direct recording of ionic currents from cell surface ion channels
Planar Lipid Bilayer techniques - Direct recording of ionic currents from intracellular ion channels

Question 2

What causes ion channels to open?

Answer 2

Voltage - Changes in membrane potential cause the channel to open
Ligand - Chemical will bind to the receptor causing a conformation change opening the channel
Stretch: Mechanosensitive channels (found in bacteria)
Light: Channelrhodopsin

Question 3

What is channel gating

Answer 3

It is how the channel opens and closes.

Question 4

What is signal channel conductance

Answer 4

How ‘good’ the channel is at letting through current

Question 5

What is macroscopic ionic current?

Answer 5

The whole cell current. It is equal to the product of the number of channels within the membrane.

Question 6

Name two channel inhibitors

Answer 6

For sodium - tetrodotoxin

For potassium - Tetraethylammonium

Question 7

What are the pathologies that arise from calcium channels working incorrectly in cardiac myocyte

Answer 7

Apoptosis
Ischaemia
Excitotoxicity
Cardiac arrhythmias
Malignant Hyperthermia

Question 8

Describe a channel mutation that leads to arrhythmia

Answer 8

This arises to mutations in the RyR2 gene. It causes dysfunction of this molecule and cause CPTV (an arrhythmia heart condition).

Question 9

Describe a channel mutation that leads to malignant hyperthermia

Answer 9

A point mutation in the gene goging for RyR1 channel leads to a pharmacogenetic disorder of skeletal muscle. This results in a severe reaction to commonly used anaesthetics and depolarising muscle relaxants. However this only becomes apparent in surgeries and is fatal if untreated

Question 10

Describe some of the symptoms of CPVT

Answer 10

Dizzy spells, fainting episodes and sudden cardiac arrest

Question 11

Describe some of the symptoms for malignant hyperthermia

Answer 11

Muscle ridigity
High fever
Increased acid level
Rapid heart rate.
Important as it is a genetic disorder

Question 12

Why is it important to study ion channels?

Answer 12

Ion channel properties are unique so it allows for functional identification of channels. This is important when looking at the action of drugs or looking for single point mutations that give rise to pathologies due to altered channel function.