Ion channels

Question 0

How can to class ion channels by physiology?

Answer 0

Gating mechanism; voltage, ligand, ion, metabolic factor, mechanical, thermal
Ion selectivity; sodium, calcium, potassium, chloride, any ion, any monovalent cation, any cation
Kinetics; fast or slow activating, transient or sustained

Question 1

Difference between ion channels and transporters?

Answer 1

Ion channels; can’t move ion against conc grad, have a faster transport rate, exhibit Nernst Goldman behaviour, have gating behaviour

Question 2

What are the exemptions to the physiological classifications?

Answer 2

NMDA..a ligand gated ion channel that shows voltage dependence
Veratridine a drug that can open voltage gated sodium channels

Question 3

How can you practically use the Nerst/Goldmann equations to determine a channels selectivity? Use GABA as an example!

Answer 3

Apply GABA at…
very -ve vm and you get an inward current
At -80mv and you get no current flow
At more positive vm, outward current flow.

Plot. Where there is no current flow…if it equals ECl then you know that GABA binds and either produces second messenger which open Cl channel or binds Cl channel.

And if change [cl-]o and still is backed up by adjusted Nerst eqn then defo a cl channel

Question 4

How do you classify an ion channel by pharmacology

Answer 4

Use channel blockers, modulaters or openers.

Eg tetrodotoxin…block voltage gated sodium channels to isolate potassium channels

Question 5

How can you use biochemistry to identify an ion channel?

Answer 5

Use it to identify structure!

Question 6

Name some common permanent ions

Answer 6

Sodium, calcium, potassium, chloride

Question 7

Name some transport process ions

Answer 7

Bicarbonate, phosphate, hydrogen ion, magnesium