Transporter proteins

Question 1

What are the extracellular and intracellular concentrations of sodium?

Answer 1

Extracellular - 140mM

Intracellular - 14mM

Question 2

What are the extracellular and intracellular concentrations of potassium?

Answer 2

Extracellular - 5mM

Intracellular - 160mM

Question 3

What are the extracellular and intracellular concentrations of calcium?

Answer 3

Extracellular - 1mM

Intracellular - 100nM

Question 4

What are the relative extracellular and intracellular concentrations of chloride ions?

Answer 4

Extracellular concentration is higher than intracellular one

Question 5

Where is Na+ K+ ATPase located?

Answer 5

Plasma membrane of all cells

Question 6

What does Na+ K+ ATPase do?

Answer 6

Actively transports 3 sodium out of the cell
2 potassium ions into the cell
using energy from ATP hydrolysis

Question 7

What type of transport does Na+ K+ ATPase do?

Answer 7

Active transport

Co-transport, antiport

Question 8

What is the structure of Na+ K+ ATPase?

Answer 8

Two subunits

• alpha subunit
• beta subunit

Question 9

What does the alpha subunit of Na+ K+ ATPase do?

Answer 9

Binds sodium, potassium, ATP

Question 9

What is the structure of the beta subunit of Na+ K+ ATPase?

Answer 9

It has oligosaccharide chains on its surface

making it a glycoprotein

Question 11

What does the beta subunit of Na+ K+ ATPase do?

Answer 11

Directs the protein to the cell surface

Question 12

How exactly does Na+ K+ ATPase use the energy released from ATP hydrolysis to actively transport sodium and potassium ions?

Answer 12

ATP phosphorylares the alpha subunit

producing an intermediate transporter

Question 13

How responsible is the Na+ K+ ATPase for producing the resting membrane potential?

Answer 13

Has a very minor role

Question 14

What is largely responsible for producing the resting membrane potential?

Answer 14

Plasma membrane is more permeable to potassium ions

move out of the cell through open potassium ion channels

Question 15

How does Na+ K+ ATPase contribute to the resting membrane potential?

Answer 15

Sets up the sodium and potassium concentration gradients required

Question 16

What does the NCX do in normal conditions?

Answer 16

Transports 3 sodium ions into the cell by facilitated diffusion
Actively transports 1 calcium ion out of the cell

Question 17

What type of transport does NCX do?

Answer 17

Co-transport, antiport

Question 18

How does the NCX affect the charge of the plasma membrane?

Answer 18

One positive charge entering the cell

Question 19

What does NCX do when the membrane is depolarised?

Answer 19

Works in reverse
transports 3 sodium ions out
1 calcium ion in, both by facilitated diffusion

Question 20

What does NCX do during ischaemia? Why?

Answer 20

Works in reverse

because ATP is depleted
Na+ K+ ATPase cannot function
sodium ions accumulate inside the cell
membrane becomes depolarised

Question 21

What does NCX working in reverse lead to?

Answer 21

High intracellular calcium concentration

toxic to cell

Question 22

What are the transporters involved in controlling cell pH?

Answer 22

Na+ H+ exchanger (NHE)

Na+ dependent Cl- HCO3- exchanger (NBC)

Cl- HCO3- exchanger (AE)

Question 23

What does NHE do?

Answer 23

Transports one sodium ion into the cell by facilitated diffusion
Transports one hydrogen ion out of the cell

Question 24

What type of transport does NHE do?

Answer 24

Co-transport, antiport

Question 25

How does NHE affect the pH of a cell?

Answer 25

Raises the pH of the cell

Question 26

What does NBC do?

Answer 26

Transports one sodium ion and one bicarbonate ion into the cell Transports one hydrogen ion and one chloride ion out of the cell

Question 27

How does NHE affect the charge of the plasma membrane?

Answer 27

It doesn't | equal charges going across plasma membrane

Question 28

What type of transport does NBC do?

Answer 28

Co-transport, antiport

Question 29

How does NBC affect the pH of a cell?

Answer 29

Raises the pH of the cell

Question 30

How does NBC affect the charge of the plasma membrane?

Answer 30

It doesn't | equal charges moving across plasma membrane

Question 31

What does AE do?

Answer 31

Transports chloride ion into the cell | bicarbonate ion out of the cell

Question 31

What type of transport does AE do?

Answer 31

Co-transport, antiport

Question 33

How does AE affect the pH of the cell?

Answer 33

Lowers the pH of the cell

Question 34

How does AE affect the charge of the plasma membrane?

Answer 34

It doesn't | equal charges moving across plasma membrane

Question 35

What type of cell is rich in AE on its plasma membrane?

Answer 35

Red blood cells

Question 36

How does AE on the plasma membrane of red blood cells affect them?

Answer 36

Makes red blood cells more acidic lowers affinity of haemaglobin for oxygen released to tissues

Question 37

How does AE on the plasma membrane of red blood cells affect the blood?

Answer 37

Bicarbonate ion released into blood as pH buffer

Question 38

How is cell volume controlled?

Answer 38

By transporting osmotically active ions into/out of cells | water follows by osmosis

Question 39

What are some examples of osmotically active ions?

Answer 39

Sodium Potassium Chloride

Question 40

What are some examples of transporters decrease cell volume? How?

Answer 40

Potassium ion channels - potassium ions leave cell through them

Question 41

What are some examples of transporters that increase cell volume? How?

Answer 41

Sodium ion channels - sodium ions enter cell through them NHE - sodium ion enters cell AE - chloride ion enters cell