VPY-0025
QUESTION
At proximal convoluted tubule, Hydrogen ion is secreted into lumen by?
OPTIONS
(A) Active transport
(B) Counter co-transport
(C) Simple diffusion
(D) Co-transport
ANSWER
(B) Counter co-transport
EXPLANATION
Counter co-transport is the correct option because hydrogen ions are secreted across the apical membrane of proximal tubular cells mainly through the Na+/H+ exchanger, which exchanges luminal Na+ for intracellular H+. Active transport, simple diffusion and generic co-transport do not describe the principal apical mechanism responsible for H+ secretion here.