BIO304 > Lesson 5 > Flashcards

Lesson 5 Flashcards

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1
Q

At resting potential, the net current is ____ so
I k = -I na

A

Zero

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2
Q

Chlorine gradients across the cell change during development so it can help _____ or ____

A

Na OR K

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3
Q

RMP is a point of _____ in the membrane voltage

A

Stability

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4
Q

If the equilibrium constant difference between K and Na is large the slope will be

A

Steep

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5
Q

The ion with the larger magnitude (I) from Vm will have a large _____

A

Driving force

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6
Q

What is permeability?

A

A measure of how easily an ion can cross a membrane, depends on number of open channels NOT on gradient or voltage

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7
Q

What is conductance?

A

The permeability of the channel and the charge of the ion

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8
Q

Units for conductance (G) is ____/volt and for permeability is ___

A

Amps
Cm^2

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9
Q

Maintaining Na and K ion gradients require ____

A

Ion pumps

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10
Q

Ion pumps are transmembrane proteins that consume energy, also called

A

ATPases

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11
Q

What do ion pumps do exactly?

A

Pump ions AGAINST their conc. grad

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12
Q

What type of transport uses energy?

A

Active transport

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13
Q

For every __ Na+ out the cell, __ K+ are pumped in

A

3 Na out,
2 K in

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14
Q

Why are the ATPase pumps also called P-type?

A

Because they get phosprulated during transport cycle

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15
Q

Who was responsible for discovering the ratio between Na and K?

A

Nobel Skou

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16
Q

Explain the Na-K exchange

A
  1. Pump has high affinity for Na+ and low affinity for K+, 3 Na+ and ATP bind
  2. ADP phosphorylates channel
  3. Conf change and Na+ ions leave channel and 2 K+ bind
  4. K+ binding triggers desphosph
  5. Conf change + cycle repeats
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17
Q

Explaint the structure of the Na-K pump

A
  • Dimeric structure with one alpha subunit and one beta subunit
  • Humans have 4 alpha genes and 4 beta genes
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18
Q

Why is the Na-K pump electrogenic?

A

Because every cycle LETS OUT 1 positive charge so it contributrs to the neg RMP of the cell

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19
Q

RC Thomas impailed a ____ with ___ electrodes

A

Snail neuron, 5 electrodes

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20
Q

Explain all 5 electrodes

A
  • Li+ injection
  • Na+ injection
  • Voltage clamp
  • Recording electrode
  • Na+ sensitive electrode
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21
Q

What does a voltage clamp do?

A

It immediately corrects a charge disturbance to make sure the membrane potential does NOT change, it will inject equal or opposite charge into the neuron to stabilize it

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22
Q

RC Thomas found that:

A
  1. Injection of Na+ (NOT Li+) changes mp
  2. Ouabain blocked Na+ effect
  3. External K+ is required
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23
Q

Oubain comes from a ____ and blocks ____

A

Plant, Na/K pump

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24
Q

Which subunit is more sensitive to ouabain?

25
Keeping levels of cytoplasmic Ca+ ___ makes signalling effective
Low
26
Cytoplasmic Ca+ is good because it can bind to ______ and cause _____
Oxygen atoms (carboxyl and carbonyl groups on AA), Conformational changes
27
Cytoplasmic Ca+ is bad because it precipitates _____, trigger ____and cannot be chemically ____
CaPO4 (which can become toxic), Apoptosis, Altered
28
The levels of Ca inside vs outside is about a _______ fold difference
10,000
29
The 2 types of Ca+ pumps are PMCA and SERCA which stand for
Plasma membrane calcium ATPase, Sarcoplasmic/Endiplasmic Reticulum Calcium ATPase
30
PMCA, SERCA and Na-K ATPase are similar because they both have a ____ intermediate
Phosphorylation
31
In the PMCA pump, __ Ca+ ion is pumped OUT of the cell per cycle
One
32
How many PMCA alpha genes do humans have?
4 a1: brain/ubiquitous a2: brain and muscle a3: brain and muscle a4: broad distribution
33
In the SERCA pump, ___ Ca+ ions are pumped into the SR/ER per cycle
2
34
How many SERCA alpha genes do humans have?
3 a1: muscle contraction a2: muscle contraction, neurons a3: expressed in cardiomyocytes (heart)
35
SERCA is ____ (high or low) expressed in the SR
Highly
36
PMCA is ____ expressed at the cell membrane
Sparsely
37
SERCA and PMCA also use ____ transport
Active
38
Exchangers are ____ (faster/slower) than pumps
Faster
39
Exchangers do not obtain their energy from ___ but rather consume energy from existing ________
ATP, Ion concentratin gradients
40
Exchangers use which type of transport?
Secondary active transport
41
Secondary active transport does not use ____
ATP
42
The NCX exchanger uses the gradient from which ions?
Na+
43
NCX stands for
Na+ Ca+ exchanger
44
NCX brings ___ Ca+ for ___ Na+ in
1/3
45
Why can NCX depolarize a cell?
Because it brings in a net +1 charge which contributes to the neg RMP
46
Which exchanger is most widely distributed?
NCX
47
NCX is special because it has the ability to _____. Whichever ion has the strongest pull inward will win
Act in reverse
48
How can you know which ion is strongest?
Pull = charge x driving force
49
The ion with the greatest pull which go IN. So, for Na+ 3 (Vm-Ena) vs. Ca+ 2(Vm-Eca), ____ will go into the cell
Na
50
____ is better than NCX
NCKXX
51
NCKXX stands for
Na-Ca-K exchanger
52
For every 4 Na+ in, both ____ and ___ go OUT
K+, Ca+
53
The structure of NCX exchanger: __ transmembrane segments
9
54
Mammals have how many NCX's genes? And where they are
3, NCX1-3 NCK1: muscle NCK2&3: brain
55
The structure of NCKX: __ transmembrane proteins
11
56
Why does the N-terminus of NCKX need to be cleaved?
57
How many NCKX genes do mammals have
5, NCK1-5
58
Where is each NCKX gene located?
NCKX1: retina NCKX2: retina and brain
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