ATP-dependent Pumps And Ion Exchangers (session 3)

Question 1

What is the function of the Na+/K+ ATPase pump?

Answer 1

Forms Na+ and K+ gradients necessary for electrical excitability
Drives secondary active transport: control of pHi, regulation of cell volume, absorption of Na+ in epithelia

Question 2

Why is high intracellular [Ca2+] toxic to cells?

Answer 2

Lots of phosphate in cells due to hydrolysis of ATP, calcium+phosphate=calcium phosphate and this leads to ossification

Question 3

What are the primary active transport mechanisms for controlling resting [Ca2+]?

Answer 3

PMCA expels Ca2+ out of the cell

SERCA accumulates Ca2+ into SR/ER

Question 4

What is the secondary active transport mechanism for controlling resting [Ca2+]?

Answer 4

NCX

Question 5

What is the facilitated transport mechanism for controlling resting [Ca2+]?

Answer 5

Mitochondrial Ca2+ uniports

Question 6

How many Na+ and Ca2+ does NCX exchange?

Answer 6

3 Na+ for every 1 Ca2+

Question 7

Give examples of acid extruders in the control of cell pH

Answer 7

Na+/H+ exchanger (NHE)

Na+ dependent Cl-/HCO3- exchanger (NBC=sodium bicarbonate cotransporter)

Question 8

Give an example of a base extruder

Answer 8

Cl-/HCO3- exchanger (AE=anion exchanger)

Question 9

What is NHE inhibited by?

Answer 9

Amiloride (potassium sparing diuretic-stops K+ entering urine)

Question 10

Which enzyme induces apoptosis when [Ca2+] is too high?

Answer 10

Caspases