Active transport

Question 1

Na+ K+ ATPase in plasma membrane maintains what?

Answer 1

Low Na+ and high K+ inside the cell

Question 2

ATPase is inhibited by what

Answer 2

Vanadate

Question 3

What happens on the alpha and beta subunits?

Answer 3

Reversibly phosporylated on catalytic alpha subunit during transport.
B subunit is regulatory subunit

Question 4

The Na+K+ pump is reversibly phosphorylated on what residue on the catalytics alpha subunit during transport?

Answer 4

Aspartate

Question 5

The Na+/K+ ATPase maintains what

Answer 5

Na and K concentrations

Question 6

Mechanism

Answer 6

The pump, after binding ATP, binds 3 intracellular Na+
ions.
ATP is hydrolyzed, leading to phosphorylation of the pump at a highly conserved aspartate residue and subsequent release of ADP.
A conformational change in the pump exposes the Na+
ions to the outside. The phosphorylated form of the pump has a low affinity for Na+
ions, so they are released.
The pump binds 2 extracellular K+
ions. This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+
ions into the cell.
The unphosphorylated form of the pump has a higher affinity for Na+
ions than K+
ions, so the two bound K+
ions are released. ATP binds, and the process starts again.

Question 7

Inhibitors of the ATP pump are used where

Answer 7

In treatment of heart failure

Question 8

Explain how the inhibitors produce contraction in the heart

Answer 8

Inhibition of Na+ efflux (flowing out) leads to higher Na+ conc in cell which activates Na+Ca2+ antiporter in heart muscle. Increased Ca2+ produces contraction

Question 9

the ion gradient set up by the Na+K+ can be used to move materials into the cell through the action of what other transporter?

Answer 9

Na+ Glucose symporter

Question 10

Name 2 glucose transporters?

Answer 10

Na+ glucose symporter

Glucose uniporter

Question 11

Where do the the 2 different glucose transporters operate?

Answer 11

Opposite sides of epithelial cells