Final answer:
Without ATP, the sodium-potassium pump will remain facing the extracellular space, with sodium ions bound, as the energy from ATP hydrolysis is required for the pump to change shape and transport ions. The correct option is (a).
The correct answer is A.
Step-by-step explanation:
The question relates to the sodium-potassium pump and what happens if no ATP is present in a cell. ATP is crucial for the function of the sodium-potassium pump because it provides the energy for the protein to change shape and execute the active transport of ions. In the absence of ATP, the protein pump cannot transition between its different states required for pumping ions across the cellular membrane. Consequently, if no ATP is present:
- The pump will remain facing the extracellular space, with sodium ions bound, because it won't have received the energy from ATP required to release the sodium ions and bind the potassium ions, which is the normal action when ATP is hydrolyzed.
The correct choice is (a), which states that the pump will remain facing the extracellular space, with sodium ions bound.