L17- intro to ion channels and transporters Flashcards
(20 cards)
what is a current
delta charge/ delta time
depolarisation
changing the cell membrane to more
positive potentials
hyperpolarisation
changing the cell membrane to more
negative potentials
ca+ movement
Calcium activates many signalling
pathways, calcium movement can be from extracellular or intracellular stores
what is an ion channel
Proteins that congregate to form water filled pores
*Conduct ions very rapidly (neuronal - 100 million ions per second)
*Recognise and select specific ions
* They open and close in response to specific signals
ion channel gating
conformational change
general structural change
blocking principle
4 types of gated channels
- Ligand gated
- Voltage gated
- Phosphorylation
- Stretch/mechanotransduction
Ion movement
open ion channels move ions passively.
- determined by the concentration
gradient
what is conductance
“Conductance” is a measure of
how much charge/ how many ions
are moving through an ion channel
pharmacological targets for ion channels
- Ligand binding/gating process
- Toxins affect the gating of ion channels or may physically block
ion channels - Drugs target second messengers to affect the phosphorylation of ion channels
- Intracellular targets (e.g. ATP) that
affect ion channel opening and closing
what can membrane transporters move
ions and small proteins across the membrane - more broadly selective to ions/proteins they transport
how fast do membrane transporters move molecules
3 per second
3 types of active transporters
- P type
- V0V1 type
- ABC type
TRUE or FALSE: P type transporters are uniport
False: P type are co-transporters and include many of the pumps, which exchange ions (e.g. sodium/potassium pump)
how do secondary active transporters move ions
Don’t use ATP to transport
Use energy stored in concentration gradients
As one ion/molecule moves down it’s concentration gradient, another ion/molecule moves against it’s concentration gradient
antiport
a secondary active transporter that moves two ions in opposite directions
symport
a secondary active transporter the moves two ions in the same direction
neurons relative to extracellular space
have High intracellular concentration of K+, Low intracellular concentration of
Na+, Low intracellular concentration of Cl-
The action potential
threshold stimulus, VGIC open increase in Na+ enters cell (depolarisation), Na+ closes, VGIC open K+ open, K+ leaves the cell (repolarisation), greater K+ leaves the cell (hyperpolarization)
neurotransmission
1) Synthesis and storage of the neurotransmitter in the presynaptic
neuron
2) Release of the neurotransmitter by the presynaptic neuron into the synaptic cleft
3) Interaction of the neurotransmitter with receptors/ion channels/transporters in the post-synaptic membrane
4) Removal of the neurotransmitter
