Question

Your classmate is excited to tell you about something they just learned. There’s a toxin named ouabain that was used by East Africans to make poison arrows. “And guess what-ouabain kills people by blocking the sodium/potassium pump that we learned about in BILD 1!” But your classmate is confused about something. “The sodium/potassium pump moves sodium and potassium ions against the concentration gradients, in the opposite direction of how the ions would normally go. But in class we said that moving ions against concentration gradients was endergonic, which means that it can’t usually spontaneously happen.”You say, “The pump uses ATP.” They say, “Yeah, but how exactly is the ATP used so that the pump can move the ions in the
non-spontaneous direction?”

Explain to your classmate the mechanism that allows the sodium/potassium pump to use ATP to have the energy to move the ions in the non-spontaneous directions. (In other words, do not focus on movement of the ions; focus on energy and ATP.) You may want to use vocabulary such as endergonic and exergonic, spontaneous and non-spontaneous, energy, and ATP. (Roughly 4 sentences)

Answer 1

The sodium potassium pump, or Na+/K+ ATPase, is hydrolyzed by the transporter to transfer three Na+ ions out of the cell and two K+ ions into the cell. The Na+ ions bind to the transfer first, followed by ATP. The ATP is hydrolyzed and provides the energy needed to change the pump's conformation from inward to outward, leaving inorganic phosphate bound to the pump.The now externally directed pump removes the Na+ ions from the cell and helps the K+ ions to join the protein pump. The release of the phosphate group, which removes the K+ ions into the cell, induces a final conformational transition from the outward- to the inward-facing.