Which statement best describes osmosis in the digestive tract?

• A. Water movement requires energy
• B. Water moves toward lower solute concentration
• C. Water moves via bulk flow with no gradient
• D. Water moves toward higher solute concentration due to osmotic gradient

Answer: (D)

Osmosis is the diffusion of water across a selectively permeable membrane toward the side with higher solute concentration. This movement is driven by an osmotic gradient and does not require energy. In the digestive tract, solutes such as electrolytes and absorbed nutrients create gradients across the intestinal epithelium, so water follows toward the side with more solute to help equilibrate concentrations. That’s why water moving toward higher solute concentration due to an osmotic gradient best describes osmosis. The other statements imply energy use, movement toward lower solute concentration, or bulk flow without a gradient, which aren’t characteristics of osmotic water movement.