Kidney function - active transportWatch
The contents of a cell are higher in sugar and ions than the solution passing through the tubule. As such, the concentration gradient favors movement of sugar/ions into the tubule, rather than re-absorption.
It's like entering a packed car in the Tube during rush hour, (car = cell, station = tubule). Harder to get into a packed car than to leave it.
it says here that active transport is required to reabsorb sugar and sufficient ions back in to the blood from a nephron. Im not sure why? could someone elaborate please? :-)
Active transport is the movement of molecules from an area of low concentration to high concentration (against a concentration gradient).
We need to absorb all of the sugar (glucose) for respiration and energy, and ions for carrying specific functions in the body.
However only a small amount of ions is needed, otherwise there will be excess ions that wont be used.