Water Absorption in the Large Intestine: Osmosis, Active Transport & Cotransport

The correct answer is D: all choices are correct.

Water movement out of the large intestine can occur through osmosis, active transport, and cotransport. Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. Active transport is the movement of molecules against a concentration gradient, requiring energy input. Cotransport is the movement of two or more molecules across a membrane simultaneously, with the movement of one molecule driving the movement of the other. In the large intestine, water can be absorbed through osmosis as a result of the high concentration of solutes in the intestinal lumen. Active transport of ions, such as sodium and potassium, can also create an osmotic gradient that drives water absorption. Additionally, cotransport of sodium and glucose or other solutes can facilitate water absorption.