Final answer:
Solvent drag is the process during reabsorption in the PCT where water carries dissolved substances, facilitated by osmotic pressure gradients due to active transport of ions.
Step-by-step explanation:
During reabsorption from the Proximal Convoluted Tubule (PCT), water can carry dissolved substances by the process of solvent drag. Solvent drag occurs when water moves through the nephron and carries with it dissolved substances, primarily due to osmotic pressure gradients established by the active transport of ions such as sodium (Na+).
This process is distinct from active transport, where substances are moved against their concentration gradient using energy in the form of ATP, and facilitated diffusion, where substances move down their concentration gradient with the help of a carrier protein. Solvent drag is part of the passive transport processes that contribute to the reabsorption of water and solutes within the kidneys.