Ion Channels Flashcards

1
Q

What causes changes in membrane potentials?

A

The movement of ions through the plasma membrane

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2
Q

Can ions pass through plasma membrane?

A

Not by itself, it needs an ion channel.

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3
Q

What is the difference between ion channels and pumps/active transporters?

A

Ion channels allow diffusion down electrochemical gradient (no energy); Pumps move ions against electrochemical gradient (energy)

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4
Q

What biological processes depend on ion channels

A
  1. neuronal signaling/sensory transduction
  2. muscle contraction
  3. regulation of salt/water balance
  4. fertilization
  5. cell proliferation
  6. cell death
  7. hormone secretion
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5
Q

What are channelopathies?

A

They describe severe and muscle diseases due to defects in ion channels

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6
Q

What is Long QT Syndrome?

A

A rare congenital heart disease, caused by a prolonged QT interval on electrocardiogram because of delayed repolarization after action potential

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7
Q

What causes Long QT Syndrome?

A

Mutations in voltage-gated K channels

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8
Q

What are important ion channel features?

A
  1. found in all excitable cells
  2. different subunits arrangements
  3. more or less ion selective
  4. regulated or not
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9
Q

What is nicotinic acetylcholine receptor?

A

It is an pentameric ion channel with 4 membrane-spanning regions that binds acetylcholine

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10
Q

What is ion selectivity?

A

Whether an ion channel is specific for an ion, or lets any ions with a specific charge through

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11
Q

What are the modes of activation?

A
  1. Channels are activated by physical changes in the cell membrane (ie. voltage gated sodium channel and stretch-activated calcium channel)
  2. Channels activated by ligands (ie. nicotinic acetylcholine receptor and cGMP-activated sodium channel)
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12
Q

How do voltage-gated ion channels work?

A

They undergo conformation changes in response to changes in membrane potential

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13
Q

How many domains does the voltage-gated sodium channel have? How many membrane-segments does each domain have?

A

4 domains; 6 membrane-spanning segments

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14
Q

What do ligand-activated ion channels do?

A

They transduce a chemical signal into an electrical signal; activated by neurotransmitters

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15
Q

What is glutamate?

A

It is a neurotransmitter that can bind to multiple receptors (ionotropic or metabotropic)

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16
Q

What is ionotropic?

A

ion channel

17
Q

Metabotropic?

A

G-protein coupled receptors that activate or inhibit other channels via signaling

18
Q

What are the 3 ionotropic glutamate receptors?

A

NMDA, AMPA, Kainate
(NMDA permeable to Na, K AND Ca)

19
Q

How do you measure single channel currents?

A

Electrophysiological recording methods

20
Q

What are the electrophysical recording methods?

A
  1. Extracellular recording (looks at firing behavior of neurons)
  2. Intracellular recording (looks at membrane potential)
  3. patch-clamp recording (looks at single ion channel current)
21
Q

Who developed patch-clamp current?

A

Erwin Neher and Bert Sakmann

22
Q

Why is it important to know the structure of ion channels?

A
  1. To understand how ion channels work and how they are regulated
  2. To develop drugs to manipulate ion channels
23
Q

What are important techniques that reveal ion channel structural information?

A
  1. Biochemical and molecular
  2. Biophysical methods
  3. Computational Methods
24
Q

What are the different structures that can form pores?

A
  1. Hetero-oligomer
  2. homo-oligomer
  3. Single polypeptide that spans the membrane several times
25
What are the two types of acetylcholine receptor?
1. Nicotinic acetylcholine receptors (nAChR, “ionotropic") are responsive to nicotine 2. Muscarinic acetylcholine receptors (maChR, “metabotropic” ) are responsive to muscarine
26
What are the pentameric channel subunits?
2 alpha subunits, 1 beta, 1 gamma, and 1 delta.
27
What two animals were helpful in helping purify nAChR?
pacific electric ray and bungaraus multicinctus
28
How did they reveal structure of AChR?
ulta-low temperature electron microscopy and computational image analysis
29
In voltage-activated ion channels, what acts as the voltage sensor?
The S4 segments; they are positively charged so depolarization causes the S4 segment to move to the outside of the cell
30
In voltage-activated sodium channels, what is selective for ions
P regions.
31
Know how to draw resting state and depolarization and S4 segments of voltage-activated ion channels.
S4 closer to negative inside; S4 closer to negative outside