Chapter 5: Ion Channels Flashcards Preview

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Flashcards in Chapter 5: Ion Channels Deck (16)
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1
Q

ion channel properties

A
  1. recognize specific ions
  2. open/close in response to a specific electrical, mechanical, or chemical signal
  3. conduct ions across the membrane
2
Q

properties

A

when open they allow ions to pass passively

-ions cross membrane because of concentration gradient or electrical gradient

3
Q

electrical gradient

A

-ion mvmt is affected by electrical charge differences. ions tend to move toward opposite charge

4
Q

polarization

A
  • separation of charges

- depolarized vs hyperpolarized

5
Q

ion channels are not the same as pumps

A
  • pumps use active transport (sodium/potassium)
  • pumps transport ions against their electrical and chemical gradients
  • pumps undergo a conformational change (slower)
  • dont have a pore, do not look like channels
6
Q

how are ion channels selective (way #1)

A
  • ions attract water
  • oxygen of water is little negative, water little positive
  • K+ is slightly bigger molecule, but with water shell Na+ is bigger molecule
  • pore size reflects molecule size (with water shell)
7
Q

way #2

A
  • selectivity filter
  • amino acid located in pore that attract specific ions
  • ex Na+ sheds H2O shell for a moment, continually propelled through by concentration and electrical gradient
8
Q

patch clamp technique

A

way to detect mvmt of ions through a channel
-glass pipet used to pull membrane up a little bit into pipet, small enough to select for 1 channel. reads difference in ion concentration

9
Q

open and closing of ion channels

A

-requires a confirmation change (change in one region, major structural change, blocking particle-ball and chain)

10
Q

ligand gating

A
  • control of opening and closing
  • molecule like NT, or molecule that binds to extracellular portion and causes gate to open
  • does not enter cell
  • agonist: drugs that facilitate postsynaptic effects (opens ion channel)
  • antagonist: drugs that block post-synaptic effects
11
Q

direct vs indirect ligand gated channels

A
  • direct: competitive binding (of agonist/antagonist and the neurotransmitter)
  • indirect: non-competitive binding (neurotransmitter and agonist bind to separate locations)
12
Q

phosphorylation gating

A

-phophate binds and activates channel (from inside)

13
Q

voltage gated channels

A

change in membrane potential opens gate
-(+) charged aa part of channel structure. normally attracted to inside of cell because of (-) resting potential, keeps gate closed. AP comes along, changes resting potential, aa moves position and opens channel

14
Q

touch gated ion channel

A

pressure opens gate, touch/stretch

15
Q

refractory period

A
  • most ion channels enter a stage of inactivation
  • due to voltage
  • due to Ca++ binding
  • -ca++ regulated through negative feedback. comes in, shuts itself off
16
Q

inactivation of Na+ channel

A
  • ball and chain, slow
  • moves up and closes hole, prevents Na+ from entering
  • channel remains inactivated until repolarization