Digestion and gastrointestinal function
Digestion of carbohydrates
Carbohydrates include sugars, starches and fiber. They are essentially long chains of saccharides (simple molecules like glucose). Enzymes such as amylase and disaccharidases help breakdown these chains to single molecules that can be absorbed by the intestines.
Amylase is a protein (or enzyme) that helps break down long chains of saccharides. It is found in breastmilk and saliva. It is also secreted into the intestines by the pancreas.
Disaccharidases are proteins that help break 2-unit groups of saccharides into separate molecules. Lactose (the main carbohydrate in milk) requires a disaccharidase called lactase for digestion. The disaccharidases are found in the walls of the intestines.
Monosaccharides (such as glucose, galactose and fructose) can be absorbed by the intestinal wall directly with the help of water and sodium.
An excess of saccharides can cause diarrhea. This is how some constipation medicines like lactulose (a disaccharide) work. Excess fruit juice (fructose) or "sugar-free" foods (sorbitol) can also cause diarrhea for this reason.
Digestion of lipids
Lipids in milk provide about 50% of the energy requirements for infants. They contain more than twice the number of calories per gram when compared to carbohydrates and proteins.
Lipase is a protein that helps breakdown lipids (fats) for digestion. Lipase is found in breastmilk and is produced by the tongue, stomach and pancreas.
Bile acids are chemicals produced by the liver that are excreted into the intestines. They help break down fat droplets that can be digested and absorbed more easily.
Digestion of proteins
Pepsin is a protein in the stomach that is activated by stomach acid to break down proteins.
The pancreas also makes enzymes (such as trypsin and chymotrypsin) that are secreted into the small intestines to help break up protein molecules.
Enzymes in the small intestinal walls complete the breakdown of proteins into small units called amino acids which are absorbed into the blood.
Absorption of vitamins and minerals
Vitamins and minerals are absorbed directly through the intestinal walls into the blood.
Last Updated (Friday, 26 June 2009 02:27)