Membrane Permeability Flashcards
What changes in Gibbs free energy will passive diffusion have?
Negative
What change in Gibbs free energy will active transport have?
Positive
Hydrolysis of ATP gives the cell how much energy under standard conditions?
-31kJ/mol
What is the approximate intracellular conc of Na+?
12mM
What is the approximate extracellular conc of Na+?
145mM
What is the approximate intracellular conc of Cl-?
4.2mM
What is the approximate extracellular conc of Cl-?
123mM
What is the approximate intracellular conc of Ca2+?
10^-7M
100nM
What is the approximate extracellular conc of Ca2+?
1.5mM
What is the approximate intracellular conc of K+?
155mM
What is the approximate extracellular conc of K+?
4mM
Describe a uniporter
Transports one ion/molecule in a single direction
Describe a symporter
Transports 2 (or more) ions/molecules at the same time in the same direction
Describe an antiporter
Transport of one type of ion/molecule in one direction whilst transporting another type of ion/molecule in the opposite direction
What effect does ATP have on the Na+/K+ ATPase pump?
ATP phosphorylates an aspartate residue on the transporter itself
In the Na+ pump, which subunit is responsible for the function and which is the signal to insert it in the membrane?
Alpha subunit = function
Beta subunit = signal
How is the majority of the RMP set up?
K+ diffusion through channels out of the cell
Describe PMCA
Calcium uniporter in the plasma membrane to extrude calcium
Primary active transporter
High affinity
Low capacity
Describe NCX
Antiporter
Secondary active transporter on the plasma membrane
Drives 1 calcium out for every 3 sodium in
Low affinity
High capacity
Describe NHE
Antiporter
Secondary active transporter
1 H+ out for every 1 Na+ in
Important for pH regulation
Which calcium transporter can reverse and when?
NCX reverse when the membrane is depolarised
3Na+ out for 1Ca2+ in
What happens to NCX in ischaemia?
ATP is depleted
Na+ pump inhibited
Membrane becomes depolarised
NCX reverses
Which transporters act as acid extruders?
NHE
NBC (HCl out, NaHCO3 in)
Which transporter acts as a base extruder?
AE (anion exchanger)
Which transporter in activated by growth factors?
NHE
Which transporter does amiloride inhibit?
NHE
What is a diuretic?
Any substance that increases the production of urine as it is a treatment for hypertension.
Where is Na+ reabsorbed in the kidneys?
Ascending limb
DCT
Cortical collecting duct
Which transporter type do loop diuretics inhibit?
NKCC2 transporters in the ascending limb
Which transporter type does amiloride inhibit in the kidneys?
ENaC in the DCT and collecting ducts
Why must VG ion channels have charged proteins with the channel?
Voltage difference in the membrane changes the conformation of the protein so that the ion channel opens
