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BIO304 > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Channels that conduct Na+ have what effect on the cell?

A

Depolarization

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2
Q

Channels that conduct K+ have what effect on the cell?

A

Hyperpolarization

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3
Q

Channels that conduct Ca2+ have what effect on the cell?

A

Depolarization (Ca2+ signalling)

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4
Q

Channels that conduct Cl- have what effect on the cell?

A

Depolarization or hyperpolarization, depending on gradient

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5
Q

Where are nicotinic acetylcholine receptors expressed?

A

Vertebrate neuron-muscle synapses (neuromuscular junctions), vertebrate and invertebrate neurons

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6
Q

What are the classical modecular techniques for characterizing ion channels and receptors? (4)

A
  1. Biochemically isolate and identify the channel protein and its subunits
  2. Determine the channel’s protein and mRNA sequences
  3. Clone the channel coding sequence and use that to express the channel in cells for electrophysiological characterization
  4. Make mutations in the channel coding sequence to test hypotheses about how specific amino acids might contribute to its function
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7
Q

What was used to purify nACh receptors from Torpedo cell lysates?

A

alpha-bungarotoxin

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8
Q

How many subunits make up an nACh receptor?

A

5

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9
Q

How many transmembrane helices are in an nACh receptor?

A

4

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10
Q

What are transmembrance helices made up of?

A

Hydrophobic amino acids

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11
Q

What is characteristic of cys-loop channels? (2)

A

5 subunits, 4 transmembrane helices

Extracellular loop formed by disulphide bond between 2 cysteine amino acids

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12
Q

Are GABA receptors anionic or cationic?

A

Anionic

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13
Q

Are glycine receptors anionic or cationic?

A

Anionic

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14
Q

Are serotonin receptors anionic or cationic?

A

Cationic

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15
Q

Are MOD-1 (serotonin) receptors anionic or cationic?

A

Anionic

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16
Q

Are glutamate-gated receptors anionic or cationic?

A

Anionic

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17
Q

Are EXP-1 (GABA) receptors anionic or cationic?

A

Cationic

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18
Q

What are cys-loop receptors also referred to as? (2)

A

Ionotropic receptors

Ligand-gated channels

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19
Q

What are cholinergic neurons?

A

Neurons that secrete acetylcholine

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20
Q

What are serotonergic neurons?

A

Neurons that secrete serotonin

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21
Q

What are GABAergic neurons?

A

Neurons that secrete GABA

22
Q

What are glycinergic neurons?

A

Neurons that secrete glycine

23
Q

What is x-ray crystallography?

A

Make crystal of protein, use x-ray diffraction (like a projector slide) to infer protein stucture

24
Q

What is cryo-electron microscopy?

A

Cryogenically freeze sample and image with electron beam

25
Q

What makes up a selectivity filter in pore-loop channels?

A

4 P-loops which project amino acids into pore

26
Q

What is a K_IR protein?

A

Inward rectifying potassium channel

27
Q

Tandem duplication of a K_IR protein resulted in…

A

2-pore K+ channels

28
Q

Inversion and addition of a TMH to K_IR protein resulted in…

A

Ionotropic glutamate receptors

29
Q

What is an HCN channel?

A

Hyperpolarization-activated cyclic nucleotide-gated channel (activated by hyperpolarization, cAMP, and cGMP)

30
Q

What is a TRP channel?

A

Transient receptor potential channel (activated by light, chemicals, osmotic pressure, temperature)

31
Q

What is a small conductance K+ channel (SK)?

A

Ca2+ or depolarization activated K+ channel with a calcium sensor at C-terminus

32
Q

What is a big conductance K+ channel (BK)?

A

Ca2+ or depolarization activated K+ channel that directly binds calcium at C-terminus

33
Q

What are Na_V channels?

A

Voltage gated Na channels

34
Q

What are Ca_V channels?

A

Voltage gated K channels

35
Q

What are NALCN channels?

A

Non-selective leak channels

36
Q

Addition of a voltage sensor to K_IR resulted in…

A

Voltage gated channels

37
Q

Addition of Ca2+ sensitive modules to K_IR resulted in…

A

SK and BK channels

38
Q

Duplication of a 2-pore channel resulted in…

A

4-domain channels

39
Q

How do K_IR channels select for K+?

A

Carbonyl oxygens projected from P-loops into pore which minic hydration shell oxygens surrounding K+ in solution

40
Q

What are two selectivity filter motifs in Ca_V channels?

A

EEEE and EEDD

41
Q

What is the selectivity filter motif in Na_V channels in humans?

A

DEKA

42
Q

What are two selectivity filter motifs in Na_V channels in earlier invertebrates?

A

DKEA and DEEA

43
Q

Describe the sliding helix model

A

At rest, S4 helix repelled into membrane by extracellular cations and attracted into membrane by intracellular anions (closed channel)
Upon depolarization, S4 helix slides through membrane and creates an outward ‘cation current’

44
Q

Describe N-type inactivation

A

“Ball and chain model”, cytoplasmic N-terminal structure moves in to plug pore. Fast.

45
Q

Describe C-type inactivation

A

Conformatinal changes through channel structure close pore. Slow.

46
Q

How many connexins/pannexins/innexins make up a hemi-channel?

A

6

47
Q

Which of the following can form gap junctions? Connexins, innexins, pannexins

A

Connexins and innexins

48
Q

What induces hemi-channel opening?

A

Membrane depolarization

49
Q

What are hemi-channels permable to?

A

ATP outward

Dyes inward

50
Q

What are the functions of gap-junctions? (2)

A
  1. Mediate electrical coupling between cells

2. Permit sharing of resources (soluble membrane impermeable molecules)

51
Q

What are the functions of hemi-channels? (2)

A
  1. Mediate release of signaling molecules such as ATP and glutamate
  2. Activate ATP-gated cation channels (Purinergic receptors) for cell-cell (paracrine) and self (autocrine) signaling

BIO304 (15 decks)

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