Although not as well known as the mouth, esophagus, stomach, small and large intestines, the pancreas is an integral part of the digestive system. It is also one of the most protected organs in your body. The pear-shaped pancreas hides between the stomach and the spine, and is surrounded by the diaphragm, intestines, liver and spleen from all sides. Your pancreas produces three all-important digestive enzymes that break down the complex proteins, fats and carbohydrates in your meals for your body to absorb and use.
Dietary protein from the hamburgers, poultry, steak, fish and beans that you eat is made up of large macromolecules that can only be absorbed after digestion into individual amino acids. While the stomach produces pepsin, an enzyme that starts the process of breaking down dietary protein, the pancreas produces trypsin and chymotrypsin, two protease enzymes that digest most of the dietary protein while inside the small intestine. Because these potent enzymes have the ability of digesting the pancreas itself, they are secreted and delivered to the small intestine in their inactive forms, trypsinogen and chymotrypsinogen.
Action of Pancreatic Proteases
Activation of pancreatic proteases occurs in the small intestine by the action of enterokinase, an intestinal enzyme that converts trypsinogen into trypsin. Trypsin then goes on to activate chymotrypsinogen, changing it into chymotrypsin. Trypsin and chymotrypsin digest the large protein macromolecules into smaller peptides. Two other proteases produced by the pancreas, carboxypeptidase and elastase, further break down the partially digested protein into dipeptides and tripeptides. In the final step of protein digestion, another enzyme produced by the pancreas, pancreatic peptidase, splits some of these peptides into individual amino acids.
The pancreas also produces pancreatic lipase, an enzyme essential for the digestion of dietary fat. However, the action of pancreatic lipase is dependent on the release of bile from the liver. Bile emulsifies fat, suspending it as small droplets in the water-based digestive juices of the small intestine. Pancreatic lipase acts on these dispersed droplets of fat, and digests them to release monoglycerides and free fatty acids, which the body absorbs and utilizes.
In addition to pancreatic protease and lipase, the pancreas produces pancreatic amylase, an enzyme that digests the carbohydrates in your food. Starch, the form of carbohydrate in foods such as bread, pasta and potatoes, is a polysaccharide made up of many units of glucose. Pancreatic amylase breaks the polysaccharides into maltose, a disaccharide or sugar molecule comprised of two glucose units. Breakdown of complex starches into simple sugars by the action of pancreatic amylase is critical for digestion of carbohydrates before they can become a source of energy for your body.
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- The Breakdown of Triglycerides in the Small Intestine
- The Major Enzymes in the Stomach
- Does Fat Take Longer Than Protein to Digest?
- How the Absorption of Fat Differs From That of Carbohydrates