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Semester 2 - Membranes and Receptors > Session 2.2 - ATP - Dependent Ion Pumps and Ion exchangers > Flashcards

Session 2.2 - ATP - Dependent Ion Pumps and Ion exchangers Flashcards

1
Q

Give the free ion distribution of Na+, K+, Ca2+ and Cl- inside the cell

A

Na+ - 10mM
K+ - 160mM
Ca2+ - 1 x 10^-4mM
Cl- - 3 mM

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2
Q

Give the free ion distribution of Na+, K+, Ca2+ and Cl- outside of the cell

A

Na+ - 145 mM
K+ - 4.5mM
Ca2+ - 1.5mM
Cl- - 114 mM

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3
Q

Describe the process of the Na+/K+-ATPase pump

A
  • Exchanges 3 intracellular Na+ for extracellular 2K+
  • Creates high intracellular K+
  • Antiport protein
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4
Q

What does the Na+/K+-ATPase pump drive?

A

Processes of secondary active transport via formation of Na+ concentration gradient

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5
Q

Why must levels of Ca2+ in cells be controlled?

A

High Ca2+ toxic to cells

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6
Q

What is SERCA? Describe its process (4)

A
  • Antiport protein
  • High affinity low capacity for Ca2+
  • Accumulates Ca2+ into the Sarcoplasmic reticulum/Endoplasmic Reticulum in exchange for H+
  • Primary active transport: ATP hydrolysis
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7
Q

What is PMCA?

A
  • Antiport protein
  • High affinity, low capacity for Ca2+
  • Intracellular Ca2+ exchanged for extracellular H+ (expels Ca2+)
  • Primary active transport: ATP hydrolysis
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8
Q

What type of active transport is demonstrated by NCX?

What is its normal role?

A
  • Secondary active transport

* Expelling Ca2+ during cell recovery

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9
Q

What is the process of transport for NCX?

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

* Electrogenic - current flows in direction of Na+ gradient

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10
Q

What is NCX dependent on?

A

Membrane potential

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11
Q

What happens to NCX in depolarised cells?

A

The normal mode of operation is inhibited and reversed, so Ca2+ enters cell.

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12
Q

What role does NCX have in ischaemia?

A
  1. ATP depleted due to lack of O2
  2. Sodium pump inhibited – no movement of Na+ out of cell
  3. NCX reverses, as outside negative: Ca2+ in, 3 Na+ out
  4. High Ca2+ toxic to cell – activates potent enzymes
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13
Q

What is the process of NHE cotransporter?

A
  • Na+ in, H+ out

* Gradient follows Na+ - no ATP hydrolysis

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14
Q

What does the NHE contransporter regulate?

A

o Cell volume i.e. cell swelling: increase ion efflux – water follows by osmosis, cell shrinkage: increase ion uptake

o pH

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15
Q

What is the NHE cotransporter activated and inhibited by?

A
  • Activated by growth factors/ inhibited by amiloride
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16
Q

What is NBC?

A
  • Na+ and HCO3- into cell, Cl- out

* Gradient follows Na+

17
Q

What occurs in cell when buffering exceeded?

A

Control of cellular pH is given to variety of plasma membrane transporters

18
Q

What is acidification of a cell opposed by?

A
  • Expelling H+ via the Na+/H+ exchanger (NHC) or the inward movement of bicarbonate via NBC.
19
Q

What is alkalisation of a cell opposed by?

A
  • Expelling bicarbonate via the anion exchanger

* HCO3- out, Cl- in

20
Q

What is AE?

A

Anion exchange

HCO3- out, Cl- in.

21
Q

Why are electroneutral transport ions used to mediate osmotic strength of cytoplasm?

A

Allows osmotic strength to be varied without effect on membrane potential

22
Q

What do cells do in response to swelling? What happens in shrinkage?

A 
Extrude ions (Na+, K+, Cl-) 
Influx ions (Na+, K+, Cl-) 
Water follows ions down osmotic gradients
23
Q

Give three ways cell swelling can be resisted

A

Conductive transporters
Contransport systems
Solute molecules exprelled

24
Q

Why is all bicarbonate filtered into proximal tubule of the kidney reabsorbed?

A

Retains base for pH buffers

25
Q

what is the main enzyme involved in bicarbonate reabsorption?

A

Carbonic anhydrase, which breaks down carbonic acid to H20 and CO2.

26
Q

Write out bicarbonate reabsorption process

A

Got it?

27
Q

What is often the first line of treatment for mild hypertension?

A

Renal control of circulating Na+ concentration

28
Q

What are the two transporters involved in the thick ascending limb, between the proximal tube lumen and the epithelial cells

A

NKCC2
and
ROMK

29
Q

What does NKCC2 do in the kidney?

A

Transfers Na+, K+ and 2Cl- into epithelial cells of proximal tubule

30
Q

What does ROMK do?

A

Absorbs K+ from epithelial cells of proximal tube into lumen

31
Q

What are the three transporters found between kidney epithelial cells and capillaries of thick ascending limb?

A

KCICT, CIC - Kb, Na pump

32
Q

What does KCICT pump?

A

K+ and Cl- from epithelial cells to capillaries

33
Q

What does CIC - Kb pump?

A

Cl - into capillary from epithelial cells

34
Q

What does the Na pump do?

A

Sodium potassium pump, 3 Na+ out, 2 K+ in

35
Q

What drug can be used to inhibit reabsorption of Na+ from proximal tube of kidney in thick ascending limb?

A

Loop diuretic, inhibits NKCC2

36
Q

What two things can Na+ reabsorbtion inhibtors treat?

A

Hypertension and Oedema

Semester 2 - Membranes and Receptors (14 decks)

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