digestion occurs in the stomach and the duodenum through the action of three main enzymes: pepsin, secreted by the stomach, and trypsin and chymotrypsin, secreted by the pancreas.During carbohydrate digestion the bonds between glucose molecules are broken by salivary and pancreatic amylase.The digestion of certain fats begins in the mouth, where short-chain lipids break down into diglycerides because of lingual lipase. The fat present in the small intestine stimulates the release of lipase from the pancreas, and bile from the liver enables the breakdown of fats into fatty acids.DNA and RNA are broken down into mononucleotides by the nucleases deoxyribonuclease and ribonuclease (DNase and RNase) that are released by the pancreas.