The sodium-potassium (Na /K ) pump functions like an anti-porter transporting Na and K across membranes using ATP. This protein spans the membrane with intracellular and extracellular domains. It has a binding site for Na , K , and ATP. An experiment was conducted to determine the locations of these binding sites. Artificial cells were created and incubated in buffers containing ATP, ouabain (or oubain), Na , and K in varying combinations inside and outside of the cell as indicated in the chart. The transport of Na and K was measured to determine activity of the Na /K pump. Experiment ATP present inside cells? ATP present outside cells? Ouabain present inside cells? Ouabain present outside cells? Was Na+transported? Was K+transported?
1 Yes Yes No No Yes Yes
2 Yes No No No Yes Yes
3 No Yes No No No No
4 No No No No No No
5 Yes No Yes Yes No No
6 Yes No Yes No No Yes
7 Yes No No Yes Yes No
Which conclusion is supported by the data?
A. Ouabain does not disrupt ATP binding to the Na+/K+ pump.
B. ATP is required for the transport of Na+ and not for transport of K+.
C. The ATP binding site of the Na+/K+ pump is located on the intracellular domain of the pump.
D. The ATP binding site of the Na+/K+ pump is located on the extracellular domain of the pump.