How does chemical digestion differ from mechanical digestion?

How does the digestion of fats differ from the digestion of carbohydrates?

• Answer:

  Digestion of fats and other lipids begin in the small intestine and relies on the production of bile. Bile contains salts, which act as detergents (emulsifiers) that aid in digestion and absorption of lipids. In the small intestine many nutrients leave the intestine through the bloodstream, some products of fat (triglyceride) take a different path: After being absorbed by epithelial cells, fatty acids and monoglycerides (glycerol joined to a single fatty acid) are recombined into triglycerides within those cells. These fats are then coated with phospholipids, cholesterol and proteins forming water-soluble glubules called chylomicrons. These globules are too large to pass through the membranes of capillaries. Instead they are transported into a lacteal, a vessel at the core of each villus of the intestinal wall. Lacteals are part of the vertebrate lymphatic system. Digestion of carbohydrates start in the mouth. Amylase, an enzyme in saliva, hydrolyzes starch and glycogen into smaller polysaccharides. This digestion continues in the stomach after the food (bolus) passes through the esophagus. In the stomach, gastric juice that have two components finishes the digestion of the carbohydrates before the intestine absorbs the broken down molecules through capillaries in the villus, before being diffused or pumped into the bloodstream. One of the components of gastric juice is HCI, which disrupts the extracellular matrix that binds cells together. Pepsin is the other component, but is more relevant in the digestion of proteins.