This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transport Across Cell Membrane, Subject name: Physiology
Which of them is TRUE about Na+-K+ pump: 
Select and explain. 
A. K+ is pumped against the gradient., B. 2K+ are exchanged with 5Na+, C. Hypercalcemia causes arrest in Na+ K+ pump., D. Increase in intracellular Na+ increases action potential.
A: K+ is pumped against the gradient.
Answer: A: K+ is pumped against the gradient. 
Explanation: Ans. is 'a' i.e. K+ is pumped against the gradient Na+-K+ pump or Na+-K+ ATPase, extrude 3 Na+ from the cell and take 2 K+ into the cell. *Thus its coupling ratio is 3:2.It pumps both Na+ & K+ against their concentration gradients by utilizing energy from the hydrolysis of ATRBecause of this differences in the charges moved in and out, it is an electrogenic pump. *Increase in intracellular Na+, decrease the height of action potential.