ATP Dependant Pumps And Ion Exchangers

Question 1

Na-K-ATPase functions:

Answer 1

Forms Na and K gradients

Drives secondary active transport
(Regulation of cell volume, [Ca], absorption of Na in epithelia, nutrient uptake from Intestine)

Question 2

Intracellular [Ca] is :

Answer 2

~ 100nM

Question 3

Extracellular [Ca]

Answer 3

1-2mM

Question 4

Primary active transport controlling [Ca]

Answer 4

PMCA and SERCA

Question 5

Secondary active transport controlling [Ca]

Answer 5

Na-Ca exchanger (removes most Ca)

Low affinity, high capacity

Question 6

Facilitated diffusion to control [Ca]

Answer 6

Mitochondrial Ca uniports

Operate at high [Ca] to buffer

Question 7

Characteristics of NCX

Answer 7

Expels Intracellular Ca during cell recovery

Exchanges 3Na for 1Ca

Electrogenic - current flows in direction of the Na gradient

Possible role in cell toxicity

Question 8

When is NCX reversed

Answer 8

A depolarised membrane potential reverses the mode of operation.

Question 9

Which transporters control cell pH?

Answer 9

Acid extruders:

Na/H exchanger (NHE)
Na dependant Cl/HCO3 exchanger (NBC)

Base extruders

Cl/HCO3 exchanger - anion exchanger

Question 10

Na/H (NHE) exchanger characteristic:

Answer 10

Exchanges extracellular Na for Intracellular H

Electroneutral

Regulates Intracellular pH

Regulates cell volume

Activates by growth factors

Inhibited by amiloride (potassium sparing diuretic)

Question 11

How is cell volume regulated?

Answer 11

Transport of osmotically active ions (Na,K,Cl,AA’s, organic osmolytes)

Water follows

Question 12

Why does the kidney reabsorb all of the bicarbonate filtered into the proximal tube?

Answer 12

To retain the base for pH buffering capacity

Question 13

Where are pumps found?

Answer 13

Only on the plasma membrane

Question 14

ATP dependant channels in parts of the cell other than the PM are called:

Answer 14

Primary active transporters