Ion channels Flashcards
Why are ion channels needed?
Ions are rebounded off the cell because of theirs and the membrane’s charge
How do ion channels work?
They are selective
Ions pass down their electrochemical gradients through the channels
List 5 types of ion channel
Potassium channels Sodium channels Calcium channels TRP channels Ligand-gated channels
How do potassium channels regulate cell excitability?
Through:
Frequency and shape of action potentials
Secretion of hormones and neurotransmitters
Membrane potential
Describe the structure of potassium channels
C terminus us larger (phosphorylation events can change the properties of the channel)
6 transmembrane domains
S4 has a positive charge = voltage centre = channel is voltage-gated
Can get different combinations of α sub-units (homomeric or heteromeric)
Give an example of how a potassium channel works
Minoxidil open potassium channels
Causes hyperpolarisation
= muscle relaxation = vasodilation
Where are sodium channels found?
Sodium channels are present in the membranes of the most excitable cells
Voltage-gated
Describe the structure of sodium channels
1 pore-forming α sub-unit , which may be associated with either 1 or 2 of the β sub-units
6 transmembrane domains
Where are calcium channels found?
In the membranes of the most excitable cells
Voltage-gated
Describe the structure of the calcium channel
Calcium channels form hetero-oligomeric complexes
The α sub-unit is pore-forming and provides the extra-cellular binding sites for practically all agonists/antagonists
What are TRP channels?
Transient receptor potential channels
Some are sensory (e.g. heat, pain)
Multiple ions can pass through the channels
What can ligand-gated channels also be known as?
Ionotropic receptors
What is the role of ligand-gated channels?
They link ligand binding to an ionic flux
Fast synaptic transmission
Describe the structure of ligand-gated channels
Sub-units combine to form pentamers (or tetramers)
Families are diverse`(different combinations of sub-units)
How do acetyl choline receptors work?
Sodium flows along its concentration gradient and causes depolarisation of cell
MUscle contraction
Increased probability of neurone firing action potential
