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4- The digestion of proteins

In the stomach, the gastric glands secrete the gastric juice. This contains HCl and pepsin: enzyme
that act on proteins and transform them to polypeptides.

5- The digestion of lipids

The pancreatic and intestinal lipases, in the presence of bile, transform lipids into fatty acids and
glycerol.

6- Intestinal absorption

The wall of the small intestine is formed of many ridges that constitute a large surface of
absorption. It allows the diffusion of the nutrients into the blood and the lymph.
The blood receives the water, the simple sugars, the mineral salts and the amino acids whereas
the fatty acids and glycerol pass to the lymph.
The nutrients circulate through the blood and lymphatic routes to reach the cells.

Digestion 31