Chapter 5: Ion Channels

Question 1

ion channel properties

Answer 1

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

Question 2

properties

Answer 2

when open they allow ions to pass passively

-ions cross membrane because of concentration gradient or electrical gradient

Question 3

electrical gradient

Answer 3

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

Question 4

polarization

Answer 4

• separation of charges

- depolarized vs hyperpolarized

Question 5

ion channels are not the same as pumps

Answer 5

• 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

Question 6

how are ion channels selective (way #1)

Answer 6

• 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)

Question 7

way #2

Answer 7

• 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

Question 8

patch clamp technique

Answer 8

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

Question 9

open and closing of ion channels

Answer 9

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

Question 10

ligand gating

Answer 10

• 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

Question 11

direct vs indirect ligand gated channels

Answer 11

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

Question 12

phosphorylation gating

Answer 12

-phophate binds and activates channel (from inside)

Question 13

voltage gated channels

Answer 13

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

Question 14

touch gated ion channel

Answer 14

pressure opens gate, touch/stretch

Question 15

refractory period

Answer 15

• 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

Question 16

inactivation of Na+ channel

Answer 16

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