Ligand-gated ion channels

Question 1

What are ion channels

Answer 1

• Transmembrane proteins which transport molecules from one side to the other

-Specific to Na+, K+ or CL- ions

-Can be open (non-gated) or use carriers (gated)

Question 2

3 essential functions of ion channels

Answer 2

1.Transport ions across membrane
2. Regulate membrane potentials
3. Ca2+ influx into cytoplasm

Question 3

What are the main structural features of all ion channels

Answer 3

-They’re made up of two or more alpha helices
- Made up of two to six subunits which surround the pore

Question 4

What are ion channels classified by

Answer 4

-Gating mechanism
-Ion selectivity of the pore

Question 5

Structure of simple (K+) ion channel

Answer 5

• 4 identical proteins that surround a central pore
  -TM’s are tightly packed on cytoplasmic side which creates a gate
• When ions flow through channel, TMs move allowing potassium through

Question 6

What can a simple ion channel be controlled by

Answer 6

-Membrane potential
- Mechanical stress
-Ligands binding to the c terminal

Question 7

What are the two functions of voltage gated ion channels

Answer 7

-Na+ and K+ create action potential in excitable cells
- Ca2+ transported into cytoplasm where second messenger elicits a cellular response

Question 8

What is the structure of a voltage gated ion channel

Answer 8

-Similar to simple ion channel
-Has additional helices forming a voltage sensing domain
-It has large polypeptides that extend into the cytoplasm
-Has a plugging mechanism

Question 9

What do transient receptor potential channels do

Answer 9

They sense chemical and physical stimuli such as hot and spicey food

Question 10

What’s the structure of a ligand gated ion channel

Answer 10

-Similar to voltage gated but controlled by the binding of a ligand

Question 11

Examples of ligand gated ion channels

Answer 11

-Calmodulin
-Cyclic nucelotide binding domain

Question 12

What is the structure of pentameric receptors and examples

Answer 12

-4 transmembrane domain regions
-Nicotinic acetylcholine receptors, serotonin receptors and GABA A receptors

Question 13

What is the glutamate family made up of

Answer 13

-4 sub-units
-An extracellular ligand binding site
-3 Transmembrane domains

Question 14

What is the ATP P2X receptor family made up of

Answer 14

• 2 transmembrane domains and a binding site for ATP