Question

uppose the vesicles with the isolated pump are inside-out of their normal orientation in the stomach. The vesicles are re-suspended in a buffer containing KCl and left overnight so that the buffer equilibrates across the membrane. Then, MgATP is added to the extravesicular medium and acidification of the vesicles is observed. However, this experiment is repeated with NaCl as a replacement to KCl in the buffer, and in that case, even when MgATP is added, acidification is not observed. Explain what type of activity this pump appears to have from these experiments solely.

* How can you tell if it is primary or secondary active transport?

Answer 1

According to the experiment, when we add potassium in the buffer then acidification takes place while when sodium no acidification takes place. We can observe two things here :-

1. Acidification is done by H+ ATPase so it is involved,

2. The acidification only in presence of potassium when ATP is added.

So we can say that it is an K+/H+ or potassium /hydrogen pump, which controls the acidity means these vesicles influence the acidity by the action of potassium and ATP.

And from above conclusion, we can say it is primary active transport because the ATP is directly involved which leads to movement of ions while in secondary active transport ATP in not directly involved instead coupled with ions, for example, sodium /potassium pump.