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

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Flashcards in M&R 2.2 - ATP Dependent Pumps And Ion Exchangers Deck (33):
1

What are the functions of the sodium ion pump?

- Form Na+K+ gradient (used in membrane potentials)

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

2

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

NCX

3

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

- 3 Na+ into cell : 1 Ca2+ out of cell

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

4

What is the function of NCX?

Expels intracellular Ca2+ during cell recovery from signalling

5

What happens when NCX becomes depolarised?

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

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

6

What happens to NCX during ischaemia/ after reperfusion?

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

7

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

NHE

8

What is the ratio of ion exchange of NHE?

- 1 Na+ in: 1 H+ out so is electroneutral

9

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

- pH regulation (is an acid extruder)
- Cell volume regulation
- Drug target for Amiloride

- Activated by growth factors

10

Name the two bicarbonate transporters and give their shorthand terms

- Na+bicarbonate-chloride cotransporter (NBC)

- Anion exchanger (AE)

11

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

- Alkalinises cell

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

12

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

- Acidifies cell

- 1 HCO3- out : 1 Cl- in

13

What the full name of PMCA?

Plasma membrane Ca2+ ATPase

14

What are the functions of PMCA?

- Removes 1 Ca2+ from cell and brings 1 H+ in

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

15

What is the full name of SERCA?

Sarco(endo)plasmic reticulum Ca2+ ATPase

16

What are the functions of SERCA?

- Removes 1 H+ and brings 1 Ca2+ in

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

17

What kind of active transporter are SERCA and PMCA?

- Primary active transporter

- Use ATP

18

What are the intracellular and extracellular concentrations of Ca2+?

- Intracellular = 50-100nM

- Extracellular = 2mM

19

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

- 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

Which transporters contribute to the control of cellular calcium levels?

- PMCA

- SERCA

- NCX

- Mitochondria Ca2+ uniports

21

What is the function of the mitochondrial Ca2+ uniports?

- Buffer away from cytoplasm when concentrations of Ca2+ are high

- Move H+ into inter membrane space which causes an electrical gradient

22

Which transporters are acid extruders?

- NHE - removes H+ so is protective in highly metabolising tissues

- NBC

23

Which transporters are base extruders?

AE - chloride is also brought in therefore acidifying

24

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

- 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

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