Question

1. what is the function of na+-k+ atpase pump on the basement membrane of proximal tubule?

a. reabsorb na+
b. secrete k+
c. reabsorb cl-
d. secrete h+

1. which segment of renal tubules has the greatest amount of na+ reabsorption ( )

a. proximal tubule
b. extensive ascending branch of loop
c. distal tubule
d. collecting tube

Explanation:

Question 4

The Na⁺ - K⁺ ATPase pump on the basement membrane of the proximal tubule is mainly responsible for reabsorbing Na⁺. It uses ATP to transport Na⁺ out of the cell and K⁺ into the cell, creating a gradient that drives Na⁺ reabsorption from the tubule lumen. Option B is incorrect as it's more about K⁺ handling in other parts, option C is about Cl⁻ reabsorption mechanisms not directly by this pump, and option D is about H⁺ secretion via other transporters.

The proximal tubule reabsorbs the largest fraction (about 65 - 70%) of the filtered Na⁺. The thick ascending limb of the loop (extensive ascending branch) reabsorbs around 25%, distal tubule around 5 - 10%, and collecting tubule a small amount. So the proximal tubule has the greatest Na⁺ reabsorption.

Answer:

A. Reabsorb Na⁺

Question 5