Question

Question: Draw the process by which water-soluble nutrients are absorbed. Include the following labels:

1. Monosaccharide

2. Amino acid

3. Absorptive cell(s)

4. Apical cell surface

5. Basolateral cell surface

6. Villus

7. Blood capillaries

8. Lacteal

Answer 1

Process of absorption of water soluble nutrients

Mainly water soluble nutrients are absorbed in small intestine. Disaccharides like maltose, sucrose and lactose are converted to glucose,glucose and fructose ,glucose and galactose respectively by maltase, sucrase and lactase before they undergo absorption in small intestine.

Proteins are converted into large polypeptides ,small polypeptides and ultimately amino acids before absorption.

About 95% of lipids are absorbed in small intestine. The small size of short chain fatty acids allows them to be absorbed by enterocytes via simple diffusion and then same take up the same path as monosaccharides and amino acids into blood capillary of villus.

The free fatty acids and monoglycerides entering the epithelial cells are re incorporated into triglycerides. Triglycerides mixed with phospholipids and cholesterol, surrounded by a protein coat forms chylomicron (water soluble lipoprotein ).Chylomicrons are transported in the lymphatic vessels (lacteal)and empty through thoracic duct into subclavian vein.In the blood stream chylomicrons are converted to free fatty acids and glycerides by lipoprotein lipase.

There are absorptive cells in the villi with an apical and basolateral cell surface.Apical cell surface faces lumen of intestine whereas basolateral surface faces away from lumen.

The amino acids, fats and monosaccharides are absorbed into the small intestine through villi having enterocytes on them .Villi are small finger like projections that increase the surface area for absorption.

Each villi have lacteal and blood vessels that help transport nutrients.