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BIOL 436 > Ion Channels > Flashcards

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
Q

What are the two types of acetylcholine receptor?

A
  1. Nicotinic acetylcholine receptors (nAChR, “ionotropic”) are responsive to nicotine
  2. Muscarinic acetylcholine receptors (maChR, “metabotropic” ) are responsive to muscarine
26
Q

What are the pentameric channel subunits?

A

2 alpha subunits, 1 beta, 1 gamma, and 1 delta.

27
Q

What two animals were helpful in helping purify nAChR?

A

pacific electric ray and bungaraus multicinctus

28
Q

How did they reveal structure of AChR?

A

ulta-low temperature electron microscopy and computational image analysis

29
Q

In voltage-activated ion channels, what acts as the voltage sensor?

A

The S4 segments; they are positively charged so depolarization causes the S4 segment to move to the outside of the cell

30
Q

In voltage-activated sodium channels, what is selective for ions

A

P regions.

31
Q

Know how to draw resting state and depolarization and S4 segments of voltage-activated ion channels.

A

S4 closer to negative inside; S4 closer to negative outside

BIOL 436 (33 decks)

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