Module 5 - Ion Pumps and Exchangers 1 Flashcards
What is estimated by the Goldman-Hodgkin-Katz equation?
Vm at rest
What is assumed by the GHK equation?
[Cl-] is in equilibrium
IK = -INa
What is the GHK equation?
Vm = (GKEK + GNaENa)/(GK + GNa)
Arrange these ions from most to least dominant in controlling the Vm: Cl, K, Na
K > Na > Cl
What is required to maintain Na+ and K+ ion gradients?
Ion pumps
What are ion pumps and what do they do?
Gene-encoded transmembrane proteins that consume energy to pump ions against their concentration gradients
What is active transport?
Energy-consuming transport processes
How do ion pumps consume energy?
Via ATP hydrolysis
Describe the numbers of K and Na ions pumped in/out of the cell by the sodium-potassium exchange pump.
3 Na+ out of the cell for every 2 K+ pumped in
What type of ATPase is the sodium-potassium exchange pump; and what does this mean?
P-type
In phosphorylated state during active transport cycle
Who discovered the sodium-potassium exchange pump?
J. C. Skou
Outline the 6 steps of the ion translocation cycle in the sodium-potassium exchange pump.
- 2 K+ dissociate to the inside and 3 Na+ bind, causing ATP to bind
- Pump is phosphorylated
- Conformational change exposes Na+ ions to the outside, affinity of Na+ binding decreases
- Na+ ions dissociate, K+ bind
- K+ binding triggers dephosphorylation
- Conformational change exposes K+ to inside, ATP binds, decreasing K+ binding affinity
Describe the structure of the sodium-potassium exchange pump.
Dimeric - one alpha and one beta subunit
What is meant by the sodium-potassium pump being electrogenic?
Every transport cycle results in the net extrusion of 1 positive charge.
What is the significance of the sodium-potassium exchange pump being electrogenic?
Pump can contribute to the negative RMP of the cell
