Primary Pumps

Question 1

What do P-type ATPases pump?
Give examples

Answer 1

Cations
K+ Na+ Ca2+ H+ Mg+

Question 2

What are P-type ATPases inhibited by?

Answer 2

Micromolar amounts of orthovanadate

Question 3

How does orthovanadate affect P-type ATPases?

Answer 3

Inhibits them by working in the same way, preventing phosphorylation

Question 4

delete

Answer 4

delete

Question 5

Where do you find Na+/K+ ATPase in animal cells?

Answer 5

In most plasma membranes of animal cells

Question 6

How many isoforms does the Na+/K+ ATPase pump have?

Answer 6

3 isoforms

Question 7

What are the general functions of Na+/K+ ATPase?

Answer 7

Maintaining high K+ and low Na+ in the cytosol

Maintains Na+ electrochemical potential via Na+ coupled transport

Question 8

What happens if Na+ builds up inside a cell?

Answer 8

It is toxic to the cell

Question 9

What is the stoichemetry of Na+/K+ ATPase pumps?

Answer 9

3 Na+ and 2 K+ per ATP hydrolysed

Question 10

What is the general structure of a Na+/K+ ATPase?

Answer 10

2 alpha (112kDa) and 2 beta (34 kDa) subunits

Question 11

Where do we find H+ ATPases?

Answer 11

All plasma membranes of plant and fungal cells

Question 12

Stoichiometry of H+ ATPases?

Answer 12

1H+ for every ATP hydrolysed

Question 13

Functions of H+ ATPase pumps:

Answer 13

Expel excess H+ produced during metabolism
Generate H+ electrochemical gradient used to drive H+ coupled transport
Maintain negative transmembrane voltage (> - 200 mV)
Regulate cytosolic pH
Acidification of extracellular medium (loosen cell walls to allow cell to expand using vacuoles)

Question 14

What is the structure of a H+ ATPase pump?

Answer 14

1 alpha (112 kDa) subunit

Question 15

What does SERCA stand for?

Answer 15

Sarcoplasmic endoreticulum Ca2+ ATPase

Question 16

Where are SERCA found?

Answer 16

Sarcoplasmic reticulum network of tubules storing Ca2+ in the muscle cell cytoplasm

Question 17

Stoichiometry of SERCA?

Answer 17

2Ca2+ per ATP hydrolysed

Question 18

Function of SERCA?

Answer 18

Restore low cytosolic Ca2+ after muscle contraction

Question 19

Structure of SERCA

Answer 19

1 alpha subunit (3 isoforms)

Question 20

Inhibitor of SERCA?

Answer 20

Thapsigargin

Question 21

What does PMCA stand for?

Answer 21

Plasma membrane Ca2+ ATPase

Question 22

Where are PMCA found?

Answer 22

Fungal, plant and animal plasma membranes

Question 23

Function of PMCA?

Answer 23

Maintain low cytosolic Ca2+ (high cytosolic Ca2+ is cytotoxic)
Central role in cell signalling

Question 24

Structure of PMCA?

Answer 24

1 alpha subunit

Question 25

Stoichiometry of PMCA?

Answer 25

Swaps 1 - 2 Ca2+ for a H+ per ATP

Question 26

Where do you find H+/K+ ATPase?

Answer 26

Plasma membrane of gastric epithelium cells (stomach wall)

Question 27

Function of H+/K+ ATPase

Answer 27

H+ secretion in to the lumen of the stomach to maintain acidic environment (=0.16 M HCl)

Question 28

Structure of H+/K+ pump

Answer 28

2 alpha and 2 beta subunits

Question 29

Stiochiometry of gastric muscosal H+/K+ ATPase?

Answer 29

2K+ for 2H+ per ATP

Question 30

What is the function of CPx pumps?

Answer 30

Work similarly to P-type pumps, but target toxic transition metals that disrupt normal physiological functions

Question 31

What kind of toxic transition metals do CPx pumps target?

Answer 31

Cu, Pb, Cd, Zn

(Copper, lead, cadmium, zinc)

Question 32

What disease is associated with systemic copper deficiency?

Answer 32

Menkes disease (neurological disease, neurones don’t have enough copper)

Question 33

What disease is associated with excessive copper accumulation in the liver?

Answer 33

Wilsons disease

Question 34

If someone is suffering from Wilsons or Menkes disease, what do they likely have a problem with?

Answer 34

CPx pumps, which target transition metals such, as in this case, copper

Question 35

What does the COPA pump do?

Answer 35

Pumps out excess copper (copper can be toxic to cells)

Question 36

What does the COPB pump do?

Answer 36

Pumps in copper when the cell is deficient in it

Question 37

Why is the pump named CPx ?

Answer 37

Amino acid motif of cysteine, proline and either cysteine, histidine or serine

Question 38

Why are the cysteine repeats important in a CPx pump?

Answer 38

To stabilise the binding of the transition metal the pump is trying to transport

Question 39

What is the purpose of region B in CPx pumps and P-type ATPases?

Answer 39

Induces conformational changes in ion binding site

Question 40

What is the purpose of region C in CPx pumps and P-type ATPases?

Answer 40

Phosphorylation site and nucleotide binding site

Question 41

What is the purpose of region J in CPx pumps and P-type ATPases?

Answer 41

Hinge to allow cytosolic regions to move and interact
Allows protein to flex to expose binding sites to ions, one side to the other

Question 42

What is the main function of V-type pumps?

Answer 42

To generate the H+ electrochemical gradient required across intracellular membranes for associated carriers to fulfil their function

(eg; for an antiporter requiring H+ to transport a neurotransmitter across a vesicle membrane to store it in that vesicle)

Question 43

Give an example for what might be powered by a V-type pump in animal cells

Answer 43

An antiporter requiring H+ to transport a neurotransmitter across a vesicle membrane to store it in that vesicle

Question 44

What is the main purpose of the ABC transporters?

Answer 44

Use energy from ATP hydrolysis to transport a wide variety of solutes in or out of the cell, allowing it to acquire nutrients or get rid of toxins or drugs

Question 45

What are MDR transporters?

Answer 45

“Multiple drug resistance” allow cell to pump toxins or drugs out of them, problematic in pathogenic or cancerous cells as it makes them resistant to these drugs/treatments (so some drugs target these transporters)

Question 46

What causes cystic fibrosis?

Answer 46

An ABC transporter wrongly acts as an ATP-gated ion channel / transporter for chloride ions