Anatomy and Physiology: Pancreatic Panacea?

Pancreatic Panacea?

The pancreas is my favorite organ, if only because mine doesn't work so well (see Figure 14.8). Beyond the endocrine role as a result of the release of insulin and glucagon (which, ironically, control the products of digestion), the pancreas is also an accessory digestive organ. Many of the enzymes used in digestion are produced here. A listing of them can be found in the following section.

In order to prevent wasteful production of enzymes, the pancreas needs to know what to produce, and when. This is due to the hormonal control of pancreatic secretions. These secretions are exocrine in nature, traveling to the small intestine through the pancreatic duct, which joins up with the common bile duct to form the hepatopancreatic ampulla.

Given that these pancreatic juices go to the duodenum, it only makes sense that the duodenum should be sending the message to make the enzymes. This chemical message is the duodenal hormone cholecystokinin, which causes the release of pancreatic enzymes. In a similar fashion, the duodenum's release of the hormone secretin causes the pancreas to release a buffer solution (pH 7.5 to 8.8) to counteract the acidity of the chyme from the stomach.

Tear 'Em Up!

Remember monomers and polymers? Well, what follows is a table of the basic enzymes produced by each of the major organs of the body, the location where that enzyme is used, the polymers they break down, and the monomers that are produced.

Digestive Enzymes—Their Production, Use, and Effects
Organ	Enzyme Produced	Enzyme Used	Substrate	Products	Organic Molecule
Mouth	Salivary amylase	Mouth and stomach	Starch	Maltose	Carbohydrates
Mouth	Lingual lipase	Mouth and stomach	Fats	Monoglyceride 2 fatty acids	Lipids
Stomach	Pepsin	Stomach	Proteins	Polypeptides	Protein
Stomach	Gastric lipase	Stomach	Fats	Monoglyceride 2 fatty acids	Lipids
Liver	Bile	Gallbladder	Fat globs	Globules (More SA/V)	Lipids
Pancreas	Pancreatic amylase	Small int.	Starch	Maltose	Carbohydrates
Pancreas	Trypsin	Small int.	Polypeptides	Peptides	Proteins
Pancreas	Chymotrypsin	Small int.	Polypeptides	Peptides	Proteins
Pancreas	Carboxypeptidase	Small int.	Peptides	Terminal amino acids	Proteins
Pancreas	Cholest. esterase	Small int.	Cholest. esters	Cholesterol and fatty acid	Lipids
Pancreas	Pancreatic lipase	Small int.	Fats	Monoglyceride 2 fatty acids	Lipids
Pancreas	Deoxyribonuclease	Small int.	DNA	DNA nucleotides	Nucleic acids
Pancreas	Ribonuclease	Small int.	RNA	RNA nucleotides	Nucleic acids
Small int.	Maltase	Small int.	Maltose	2 Glucoses	Carbohydrates
Small int.	Sucrase	Small int.	Sucrose	Glucose, fructose	Carbohydrates
Small int.	Lactase	Small int.	Lactose	Glucose, galactose	Carbohydrates
Small int.	Aminopeptidase	Small int.	Peptides	Amino acids	Proteins
Small int.	Dipeptidase	Small int.	Dipeptides	Amino acids	Proteins
Small int.	Nucleotidase	Small int.	Nucleotides (Phosphate, Sugar, and Base)	Separates Nitrogenous Base and Sugar	Nucleic acids
Small int.	Phosphatase	Small int.	Nucleotides	Removes Phosphate	Nucleic acids

You might remember that enzymes are basically large proteins with an active site where the substrate, or molecule to be digested, fits. The way an enzyme functions is by changing its shape, and, in the case of digestive enzymes, separating polymers into either monomers or smaller polymers. In the first case, sucrase breaks down sucrose, or table sugar, into glucose and fructose, which are both monomers. Larger polymers, such as starch, are digested in a multistep process; they need to first be broken down by either salivary or pancreatic amylase into small polymers (disaccharides) of maltose, and then the maltose is broken down by what else, maltase, into two molecules of glucose. This is yet another example of the division of labor.