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Neurobiology I > Ion Channels and Transporters > Flashcards

Ion Channels and Transporters Flashcards

1
Q

Central dogma of biology: 3 processes

A
  1. DNA synthesis through replication
  2. RNA synthesis through transcription
  3. Protein synthesis through translation
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2
Q

Difference between DNA and RNA in terms of number of strands

A

DNA: double-stranded
RNA: single stranded

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3
Q

Type of RNA used to make protein

A

mRNA

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4
Q

Building blocks of DNA and RNA are called ____.

A

Nucleotides

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5
Q

Building blocks of proteins are called ____.

A

Amino acids

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6
Q

A small protein is called a ____.

A

Peptide

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7
Q

What is the same for all amino acids?

A

Backbone

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8
Q

How are amino acids linked in a protein?

A

Covalent bonds

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9
Q

3 basic types of amino acid side chains

A

Neutral (non-polar), charged, polar

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10
Q

Interactions among amino acid ____ ____ drives folding of protein.

A

Side chains

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11
Q

How does the aqueous environment of the cell drive the folding of proteins?

A

Proteins will fold such that their polar side chains are on the outside and non-polar side chains are on the inside

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12
Q

Secondary structure of amino acid involves ____ driven entirely by ___ ____ sequence

A

Folding

Amino acid

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13
Q

How tertiary structure differs from secondary structure

A

Folding is more complicated

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14
Q

What type of secondary structure makes good transmembrane proteins?

A

Alpha helices

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15
Q

Domain definition

A

Functional unit of protein

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16
Q

Domains are from the same _____, so they are from the same ____.

A

Protein

Gene

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17
Q

If domains were separated, would each one retain its function?

A

Yes

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18
Q

In an alpha helix, the ____ side chains are on one side and the ____ side chains are on the other

A

Polar

Charged

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19
Q

Primary structure of a protein is determined by what?

A

Sequence of amino acids

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20
Q

What causes the alpha helix shape?

A

Interaction of side chains

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21
Q

How many alpha helices combine to form a pore? What does the pore allow?

A

5

Ions to pass through

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22
Q

Can a protein subunit fold on its own? Does it have full function on its own? Why or why not?

A

Yes

No- needs to associate with other protein(s)

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23
Q

When subunits interacting are the same, it is called ____.

A

Oligomerization

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24
Q

Quaternary structure is due to what?

A

Multiple subunits associating with each other to form functional protein

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25
Q

When a subunit associates with the same type of protein, it forms a _____.

A

Homopolymer

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26
Q

When a subunit associates with different type of protein, it forms a _____.

A

Heteropolymer

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27
Q

Two main differences between subunit and domain: level of structure, which is part of the other

A

Subunit is part of quaternary structure

Domain is part of subunit

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28
Q

4 ways that proteins can associate with a membrane

A

Transmembrane
Monolayer-associated
Lipid-linked
Protein-attached

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29
Q

Most ion channels are ____ proteins.

A

Transmembrane

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30
Q

In a lipid-linked protein, does lipid linkage cause the protein to be on one or both sides of the membrane?

A

One side of membrane

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31
Q

Trimeric G proteins are what type of membrane-associated proteins?

A

Protein-attached (attached to transmembrane protein)

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32
Q

What type of method is a more “subtle” version of voltage clamp? How is it more “subtle”?

A

Patch clamp

Suitable for the smaller neurons of most animals

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33
Q

Patch clamp can be used to record whole ____ as well as single ____.

A

Cells

Channels

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34
Q

Patch clamp studies of ion channels can be completed in genetically modified ____ ____ that express foreign ____ ____.

A

Frog eggs

Ion channels

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35
Q

When patch clamping Na channels for analysis, what must be done with K channels and how?

A

K channels must be blocked with TEA

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36
Q

In a patch clamp experiment with Na, when does inward current start and when does it go away, relatively speaking?

A

As soon as patch clamp starts

Goes away quickly

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37
Q

Patch clamp experiments tell us the _____ that a given channel will open.

A

Probability

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38
Q

When running a patch clamp experiment on a whole cell or a single Na channel, is the duration the same or different for the whole cell and the single channel?

A

Same

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39
Q

In a patch clamp experiment, at what point is the first time that there is a reasonable probability of Na or K channels opening?

A

Threshold

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40
Q

At ____ mV, there is maximum conductance for Na because there is a maximum ____ of opening.

A

20

Probability

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41
Q

At 20 mV, there is a(n) _____% chance that all Na channels will be open.

A

80

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42
Q

When patch clamping K channels for analysis, what must be done with Na channels and how?

A

Na channels must be blocked with tetrodotoxin

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43
Q

In patch clamp experiments with K channels, there is a ___ in opening, but they ___ ____ the entire time thereafter.

A

Delay

Stay open

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44
Q

When comparing a whole cell vs a single channel in a patch clamp experiment, the ____ of current changes but the ____ stay the same.

A

Magnitude

Kinetics

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45
Q

Like with Na channels, at ___ mV there is a maximum probability of K channels being ____.

A

20

Open

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46
Q

At 20 mV, there is a(n) _____% chance that all K channels will be open.

A

60

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47
Q

Plotting probability of channel opening and whole cell conductance for K and Na reveal similar or dissimilar graphs? Why? What is different between the 2 ions in regards to channel opening?

A

Similar- same properties

Kinetics of opening and closing channels are different for each ion

48
Q

Sodium current is ___ (timing), ____ (length), and ____ (direction).

A

Early
Transient
Inward

49
Q

Potassium current is ___ (timing), ____ (length), and ____ (direction).

A

Late
Sustained
Outward

50
Q

Scorpion alpha- and beta- toxins affect which ion channels?

A

Na

51
Q

Scorpion alpha-toxin affects Na current and action potential duration how? What is the mechanism by which is does this?

A

Increased length of current and action potential

Blocks inactivation of Na channels

52
Q

Scorpion beta-toxin affects Na channels how? What is the mechanism by which is does this?

A

Channel opens sooner (at rest) because its threshold is decreased
Voltage sensing properties of Na channel are changed

53
Q

Channels can be ___- or ____- gated.

A

Voltage

Ligand

54
Q

For a ligand-gated channel, what makes it open and what is a ligand?

A

Binding makes channels open

Ligand: thing that binds

55
Q

To form a functional channel, is one or many proteins necessary?

A

Either- depends on channel

56
Q

What is the function of a pore-loop in a channel and how does it work?

A

Amino acids of pore-loop line channel pore, determining which ions can pass through the channel

57
Q

What does voltage-dependence mean for a channel?

A

Has a threshold and will only open at a certain voltage

58
Q

Can channels move ions against their driving force?

A

No

59
Q

A regulatory subunit comes from the (same/different) protein that comprises the ion channel. It ____ function of the channel but (is/isn’t) required for channel to pass ions.

A

Different
Modifies
Isn’t

60
Q

Every protein has ____ carboxy terminal(s) and ___ amino terminal(s).

A

1

1

61
Q

How many alpha subunits are needed for a functional voltage-gated K+ channel?

A

4

62
Q

What subunits of the “typical” voltage-gated K+ channel aren’t required to make the channel functional?

A

Beta

63
Q

The voltage sensing region of the voltage-gated K+ channel is a ___ of the alpha subunit.

A

Domain

64
Q

At rest, the voltage sensor of the voltage-gated K+ channel is ____.

A

Closed

65
Q

Upon depolarization, what happens to the voltage sensor of the voltage-gated K+ channel?

A

Undergoes conformational change that allows ions to pass through

66
Q

What are the 3 types of voltage gated K+ channels talked about in class, and which one is the most typical?

A

Kv2.1 (most typical)
Kv4.1
HERG

67
Q

All voltage-gated channels have a voltage ____.

A

Sensor

68
Q

Kv2.1, Kv4.1, and HERG channels have how many alpha subunits? How many membrane spanning helices per subunit? How many transmembrane domains per functional channel?

A

4
6
24

69
Q

All the K+, Na+, and Ca+ channels talked about in class have _____ ____ attached to their alpha subunits.

A

Pore loops

70
Q

Kv2.1, Kv4.1, and HERG channels all have how many beta subunits? The beta subunits function as _____ subunits.

A

4

Regulatory

71
Q

What about the kinetics of the Kv2.1 channel and subsequent K+ current make it the “typical” voltage-gated K+ channel?

A

Slow to open and close

Sustained current above threshold

72
Q

For a given Kv2.1 channel, are the alpha subunits all the same type (from the same gene) or different (from different genes)?

A

Could be either

73
Q

Are the alpha and beta subunits of the voltage-gated K+ channel encoded by same or different gene(s)?

A

Different

74
Q

How is the Kv4.1 channel different from the Kv2.1 channel in terms of opening/closing and K+ current that makes it similar to the Na channel?

A

Kv4.1 channel inactivates shortly after opening

Transient K+ current above threshold

75
Q

What happens to the HERG (K+ voltage-gated channel) immediately after opening? What does this mean for K+ current with these channels in a voltage clamp experiment?

A

It inactivates

Don’t see any K+ current during voltage clamp experiment

76
Q

When does the HERG (K+ voltage-gated channel) de-inactivate? Is it slow or quick to close?

A

When Vrest is reached again

Slow

77
Q

Do HERG channels (K+ voltage-gated channel) show transient or sustained K+ current? Between what 2 points does it last?

A

Transient

Between returning to Vrest and channel closing

78
Q

K+ inward rectifying (KIR) channels: how many alpha subunits for a functional channel? How many membrane spanning helices/subunit? How many transmembrane domains per functional channel?

A

4
2
8

79
Q

Are K+ inward rectifying (KIR) channels voltage-sensitive?

A

No

80
Q

Do the K+ inward rectifying (KIR) channels have regulatory subunits?

A

No

81
Q

K+ inward rectifying (KIR) channels passes K+ current in what direction only?

A

Inward

82
Q

Because the K+ inward rectifying (KIR) channels only pass K+ current in the inward direction, conductance for K+ in these channels only occurs when membrane voltage is ____ than equilibrium potential for K. Why is it that these channels can be open at such a low voltage?

A

Less

The channels aren’t voltage dependent, so they don’t have a threshold

83
Q

The K+ inward rectifying (KIR) channels play a role in restoring the membrane potential to _____.

A

Vrest

84
Q

The Ca+2 gated K+ channels have how many alpha subunits? How many membrane-spanning helices? How many transmembrane domains per functional channel?

A

4
7
28

85
Q

How many types of Ca+2 gated K+ channels are voltage-sensitive? What is/are the name(s) of the type(s) that are?

A

1 (Type 1 only; the rest are not)

86
Q

The (intra-/extra-)cellular domain of Ca+2 gated K+ channels binds what ion? This domain functions as a ____ domain.

A

Intracellular
Ca+2
Regulatory

87
Q

For a Ca+2 gated K+ channel, the more (intra-/extra-)cellular ____ present, the more ____ current and conductance is seen.

A

Intracellular
Ca+2
K+

88
Q

The Ca+2 binding domain of the Ca+2 gated K+ channel is all part of ___ alpha subunit(s).

A

1

89
Q

High intracellular Ca+2 will let the Ca+2 gated K+ channel open when membrane potential is ___ than threshold for Kv2.1. Thus, it can cause _____ K+ current without an action potential.

A

Less

Outward

90
Q

The 2P K+ leak channels have how many alpha subunits required for a functional channel? How many membrane spanning helices per subunit? How many transmembrane domains per functional channel?

A

2
4
8

91
Q

Are 2P K+ leak channels voltage-sensitive?

A

No

92
Q

What 2 things are 2P K+ leak channels sensitive to?

A

pH

Mechanical stretch

93
Q

Do 2P K+ leak channels have regulatory subunits?

A

No

94
Q

For the 2P K+ leak channels, at what pH is the maximum conductance? Does it also open at biological pH?

A

8.0

Yes

95
Q

At Vm less than Ek, 2P K+ leak channels “leak” ____ current and at Vm greater than Ek, 2P K+ leak channels “leak” ___ current.

A

Inward

Outward

96
Q

Do the 2P K+ leak channels require an action potential to “leak” K+ current?

A

No

97
Q

The voltage-gated Na+ and Ca+2 channels have how many alpha subunits from how many proteins? How many domains, and what are they similar in structure to? How many total membrane spanning helices?

A

1 subunit from 1 protein
4 domains
Similar to single alpha subunit of voltage-gated K+ channel
24 membrane spanning helices

98
Q

For the voltage-gated Na+ and Ca+2 channels, how many voltage sensor(s) per domain?

A

1

99
Q

The voltage-gated Na+ and Ca+2 channels have a ___ subunit that functions as a ___ subunit. This subunit is encoded by the same/different gene that encodes the alpha subunit.

A

Beta
Regulatory
Different

100
Q

The voltage-gated Na+ channel has an (intra-/extra-)cellular ____ loop that functions as a ___ subunit.

A

Intracellular
Inactivation
Regulatory

101
Q

What is the only K+ channel that doesn’t have 4 alpha subunits?

A

2P K+ leak channels

102
Q

Toxins bind on the (inside/outside) of the Na channel.

A

Outside

103
Q

The inactivation domain of the Na channel is located on the (extracellular/cytoplasmic) side of the molecule.

A

Cytoplasmic

104
Q

What 2 properties are dependent upon channel being open? (Think I = g x DF)

A

Current

Conductance

105
Q

If a voltage-gated Na channel doesn’t completely inactivate, how does that affect Vm and future action potentials after an action potential is completed?

A

Vm stays close to threshold

Likely to fire more action potentials

106
Q

Thermosensitive channels: what causes what conformational change?

A

Warming of membrane causes opening of channel

107
Q

Thermosensitive and mechanosensitive channels generally pass one or both of what 2 ions?

A

Na

Ca

108
Q

Mechanosensitive channels: what causes what conformational change?

A

Stretching of membrane causes opening of channel

109
Q

When referring to active transport of ions, a pump uses ____ as energy, whereas a transporter uses ____ as energy.

A

ATP

Electrochemical gradient

110
Q

For an ATP pump, ATP _____ causes a conformational change that enables movement of ions ____ their concentration gradients. Are ions moved in the same or opposite directions? Is more than one ion required for the ATP pump to work?

A

Hydrolysis
Against
Opposite
No- can move one without the other, but still requires ATP

111
Q

For an anti-porter, energy provided by the driving force of moving ____ ion(s) ____ the gradient enables moving another ion _____ the gradient.

A

1
With
Against

112
Q

In an anti-porter, are the ions moving in the same or opposite directions?

A

Opposite

113
Q

For a co-transporter, energy provided by the driving force of moving ___-___ ions ____ the gradient enables moving another ion _____ the gradient.

A

1-2
With
Against

114
Q

In a co-transporter, are the ions moving in the same or opposite directions?

A

Same

115
Q

For the Na/K pump, how many Na and how many K are moved per 1 ATP?

A

3 Na

2 K

116
Q

The Na/K pump undergoes conformational change, allowing __ Na to enter on the _____ side of the membrane and ___ K to be released. What causes conformational change that enables Na to be released on the other side and K to bind? What causes the pump to switch back to its other side?

A 
3 
Cytoplasmic
2
Phosphorylation 
Dephosphorylation
117
Q

What do ouabain and digoxin do to the Na/K pump? How does prolonged exposure to these drugs affect the concentration gradient and membrane potential of a cell?

A

Inhibit Na/K pump

Depletes concentration gradient for K and Na, bringing Vm close to 0

Neurobiology I (18 decks)

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