How is glucose absorbed in the small intestine?
Glucose is the monosaccharide obtained by the digestion of carbohydrates (polysaccharides) and is the smallest unit. it is soluble in water. In the intestine the water is absorbed through the membrane of the microvilli due to osmotic gradient. Since blood is osmotically higher (having more salts or ions) the water will diffuse into the blood contained in the capillaries of the intestine. Along with this water the glucose also move into the circulation. If you keep more salts (nondiffusible) in the lumen of the intestine then water will not diffuse into the blood circulation (this is the principle of laxatives- most of them cotanin magnesium salts and thus will not allow the water to diffuse- more water retained in the intestine will lead to purgative or laxative action, i.e loose motion).
Glucose is absorbed by the intestinal mucosa in 1-4 hours after meal by four mechanisms: (1) active transport that requires energy (2) passive diffusion, (3) endocytosis, and (4) facilitative diffusion. However, a mixed meal containing protein, fiber and fat delays gastric emptying and takes longer time to digest and be absorbed from the intestine.
