Na-K ATPase: (A) 3 Na out / 2K in, (B) 3Na in / 2K out, (C) 2Na out / 3K in, (D) 2Na in / 3K out
Answer is A. Na+-K+ATPase, which actively moves Na+and K+ against their electrochemical gradient. The electrogenic Na K ATPase plays a critical role in cellular physiology by using the energy in ATP to extrude 3 Na+ out of the cell in exchange for taking two K+ into the cell. (REF.GANONG'S REVIEW OF MEDICAL PHYSIOLOGY 23rd EDITION page no.85.)