Membrane Permeability

Question 1

What changes in Gibbs free energy will passive diffusion have?

Answer 1

Negative

Question 2

What change in Gibbs free energy will active transport have?

Answer 2

Positive

Question 3

Hydrolysis of ATP gives the cell how much energy under standard conditions?

Answer 3

-31kJ/mol

Question 4

What is the approximate intracellular conc of Na+?

Answer 4

12mM

Question 5

What is the approximate extracellular conc of Na+?

Answer 5

145mM

Question 6

What is the approximate intracellular conc of Cl-?

Answer 6

4.2mM

Question 7

What is the approximate extracellular conc of Cl-?

Answer 7

123mM

Question 8

What is the approximate intracellular conc of Ca2+?

Answer 8

10^-7M

100nM

Question 9

What is the approximate extracellular conc of Ca2+?

Answer 9

1.5mM

Question 10

What is the approximate intracellular conc of K+?

Answer 10

155mM

Question 11

What is the approximate extracellular conc of K+?

Answer 11

4mM

Question 12

Describe a uniporter

Answer 12

Transports one ion/molecule in a single direction

Question 13

Describe a symporter

Answer 13

Transports 2 (or more) ions/molecules at the same time in the same direction

Question 14

Describe an antiporter

Answer 14

Transport of one type of ion/molecule in one direction whilst transporting another type of ion/molecule in the opposite direction

Question 15

What effect does ATP have on the Na+/K+ ATPase pump?

Answer 15

ATP phosphorylates an aspartate residue on the transporter itself

Question 16

In the Na+ pump, which subunit is responsible for the function and which is the signal to insert it in the membrane?

Answer 16

Alpha subunit = function

Beta subunit = signal

Question 17

How is the majority of the RMP set up?

Answer 17

K+ diffusion through channels out of the cell

Question 18

Describe PMCA

Answer 18

Calcium uniporter in the plasma membrane to extrude calcium
Primary active transporter
High affinity
Low capacity

Question 19

Describe NCX

Answer 19

Antiporter
Secondary active transporter on the plasma membrane
Drives 1 calcium out for every 3 sodium in
Low affinity
High capacity

Question 20

Describe NHE

Answer 20

Antiporter
Secondary active transporter
1 H+ out for every 1 Na+ in
Important for pH regulation

Question 21

Which calcium transporter can reverse and when?

Answer 21

NCX reverse when the membrane is depolarised

3Na+ out for 1Ca2+ in

Question 22

What happens to NCX in ischaemia?

Answer 22

ATP is depleted
Na+ pump inhibited
Membrane becomes depolarised
NCX reverses

Question 23

Which transporters act as acid extruders?

Answer 23

NHE

NBC (HCl out, NaHCO3 in)

Question 24

Which transporter acts as a base extruder?

Answer 24

AE (anion exchanger)

Question 25

Which transporter in activated by growth factors?

Answer 25

NHE

Question 26

Which transporter does amiloride inhibit?

Answer 26

NHE

Question 27

What is a diuretic?

Answer 27

Any substance that increases the production of urine as it is a treatment for hypertension.

Question 28

Where is Na+ reabsorbed in the kidneys?

Answer 28

Ascending limb
DCT
Cortical collecting duct

Question 29

Which transporter type do loop diuretics inhibit?

Answer 29

NKCC2 transporters in the ascending limb

Question 30

Which transporter type does amiloride inhibit in the kidneys?

Answer 30

ENaC in the DCT and collecting ducts

Question 31

Why must VG ion channels have charged proteins with the channel?

Answer 31

Voltage difference in the membrane changes the conformation of the protein so that the ion channel opens