M&R 2.2 - ATP Dependent Pumps And Ion Exchangers Flashcards

1
Q

What are the functions of the sodium ion pump?

A
  • Form Na+K+ gradient (used in membrane potentials)

- Promotes secondary active transport (pH control, cell volume and Ca2+ regulation, Na+ absorption and nutrient uptake)

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2
Q

What is the Na+Ca2+ exchanger otherwise known as?

A

NCX

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3
Q

What is the ratio of ion transport of NCX? What happens as a result of this?

A
  • 3 Na+ into cell : 1 Ca2+ out of cell

- Membrane becomes electrogenic so the current runs in the direction of the Na+ gradient

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4
Q

What is the function of NCX?

A

Expels intracellular Ca2+ during cell recovery from signalling

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5
Q

What happens when NCX becomes depolarised?

A
  • Works in reverse (3Na+ out, 1Ca2+ in)

- Lead to a high concentration of extracellular Na+ and high concentration of intracellular Ca2+

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6
Q

What happens to NCX during ischaemia/ after reperfusion?

A

The depletion of ATP causes it to become partially depolarised which can produce toxicity

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7
Q

What is the Na+H+Exchanger otherwise known as?

A

NHE

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8
Q

What is the ratio of ion exchange of NHE?

A
  • 1 Na+ in: 1 H+ out so is electroneutral
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9
Q

What are the functions of NHE? What is it activated by?

A
  • pH regulation (is an acid extruder)
  • Cell volume regulation
  • Drug target for Amiloride
  • Activated by growth factors
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10
Q

Name the two bicarbonate transporters and give their shorthand terms

A
  • Na+bicarbonate-chloride cotransporter (NBC)

- Anion exchanger (AE)

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11
Q

What is the function of NBC and how is this achieved?

A
  • Alkalinises cell

- 1 Na+ and 1 HCO3- in : 1 H+ and 1 Cl- out

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12
Q

What is the function of AE and how is this achieved?

A
  • Acidifies cell

- 1 HCO3- out : 1 Cl- in

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13
Q

What the full name of PMCA?

A

Plasma membrane Ca2+ ATPase

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14
Q

What are the functions of PMCA?

A
  • Removes 1 Ca2+ from cell and brings 1 H+ in

- Removes residual Ca2+ by having a high affinity but a low capacity

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15
Q

What is the full name of SERCA?

A

Sarco(endo)plasmic reticulum Ca2+ ATPase

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16
Q

What are the functions of SERCA?

A
  • Removes 1 H+ and brings 1 Ca2+ in

- Accumulates Ca2+ in sarcoplasmic/endoplasmic reticulum by having a high affinity but a low capacity

17
Q

What kind of active transporter are SERCA and PMCA?

A
  • Primary active transporter

- Use ATP

18
Q

What are the intracellular and extracellular concentrations of Ca2+?

A
  • Intracellular = 50-100nM

- Extracellular = 2mM

19
Q

Which three transport methods contribute to the transport of calcium ions? Why does there need to be so many?

A
  • Primary active transport e.g. SERCA
  • Secondary active transport e.g. NCX
  • Facilitated transport e.g. VOCC
  • If only one was used, the appropriate concentrations wouldn’t be able to be reached
20
Q

Which transporters contribute to the control of cellular calcium levels?

A
  • PMCA
  • SERCA
  • NCX
  • Mitochondria Ca2+ uniports
21
Q

What is the function of the mitochondrial Ca2+ uniports?

A
  • Buffer away from cytoplasm when concentrations of Ca2+ are high
  • Move H+ into inter membrane space which causes an electrical gradient
22
Q

Which transporters are acid extruders?

A
  • NHE - removes H+ so is protective in highly metabolising tissues
  • NBC
23
Q

Which transporters are base extruders?

A

AE - chloride is also brought in therefore acidifying

24
Q

How is cell volume regulated? In what environment can this be achieved?

A
  • Transport of osmotically active ions e.g. Na+ to which water follows
  • Has to be done in an ELECTRONEUTRAL environment
25
What causes swelling and shrinkage of the cell?
- Swelling = INFLUX of ions therefore more water inside | - Shrinkage = EXTRUSION of ions therefore more water outside
26
Where does renal bicarbonate absorption happen? What is the aim of this?
- Proximal tubule of the kidney Goals are: - H2CO3 retention for pH buffers - pH and cell volume regulation
27
How is Na+ retained in the proximal tubule?
- NHE transports Na+ into cell from lumen of proximal tubule - Na+ pump transfers Na+ into the capillary from the cell
28
How is H2CO3 retained in the proximal tubule?
- NHE exchanges H+ for Na+ - H+ combines with HCO3- to make H2CO3 - H2CO3 is broken down by carbonic anhydrase to form H2O and CO2 - Diffuse readily across membrane and recombine in cell - H2CO3 transported into capillary by AE
29
Which transporter is targeted in the thick ascending limb of the kidney during diuretic treatment? What is the effect of this?
- NKCC2 (Na+K+Cl- move in) - Is inhibited when loop diuretics bind - Limits reuptake of Na+ therefore less water reabsorbed - Blood volume is decreased - Decreases blood pressure
30
Which transporters are targeted in the distal convoluted tubule of the kidney during diuretic treatment? What is the effect of this?
- Thiazide inhibits Na+Cl- cotransporter and does the same as loop diuretics - Amiloride inhibits Epithelial Na+ Channel and does the same as loop diuretics
31
Which transporters are targeted in the cortical collecting duct of the kidney during diuretic treatment? What is the effect of this?
- ENaC - Na Pump - ROMK - Spironolactone inhibits therefore inhibiting aldosterone
32
What is the function of aquaporin? What stimulates this?
- A water channel, ensures efficient water uptake along with Na+ - Stimulated by ADH
33
What is Na+K+ATPase otherwise known as?
Sodium pump