Explain the Selective Reabsorption Process

1. Specialized proteins called 'transporters' are located on the membranes of the various cells of the nephron.

2. These transporters grab the small molecules from the filtrate as it flows by them.

3. Some transporters require energy, usually as ATP (active transport), while others don't (passive transport).

4. Water gets reabsorbed passively by osmosis in response to the build up of reabsorbed Na in spaces between the cells that form the walls of the nephron.

5. Other molecules get reabsorbed passively when they are caught up in the flow of water (solvent drag).

6. Reabsorption of most substances is related to the reabsorption of Na, either directly, via sharing a transporter or indirectly through a solvent drag.