Why Are Digestive Enzymes Found in Gastric Juices?
Since many of the foods we eat are complex and rich in protein and other nutrients, chemicals from the digestive system are used to break down food into smaller molecules. Each organ within the digestive system secretes its own enzymes, with the stomach secreting the gastric juices. Gastric juices are used to break down proteins, starches, and fats. The liver and pancreas also help in digesting food once it leaves the stomach and enters the intestines.
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Digestive System
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The digestive system contains a series of organs and tissues starting at the mouth and ending in the large intestine. The primary purpose of the digestive system is to ingest (eat) and digest (process) food for nutrition. Organs and tissues secrete different chemicals to aid in the processing of the food. These chemicals include enzymes, surfactants, and diluents.
Food Absorption
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Humans are omnivores, which means that we eat all sorts of foods. From meats to vegetables and everything in between, food is broken down during digestion. Our digestive system is designed to help us get the most nutrition out of everything we eat, and smaller molecules are better absorbed. However, the proteins and sugars we eat are made up of large molecules that are too big to be absorbed into the body. The chemicals in the digestive system help to break down food to its most basic molecules.
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Enzymes
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Enzymes are complex chemicals that aid in chemical reactions in the body. Enzymes speed up chemical reactions that would otherwise require more energy. This leaves more energy for the body to absorb. The creation of enzymes and adding them to the food begins at the mouth, where enzymes in saliva begin to aid in the breakdown of starches into simple sugars and meat into simpler proteins. Once in the stomach, gastric enzymes are added.
Gastric Juices
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Gastric enzymes include pepsin, which breaks down proteins even further into amino acids small enough to be absorbed later in the intestines. Gelatinase collapses the connective tissues in meat. Lipase reduces fats (lipids) into more basic oils. Another enzyme, renin, breaks down proteins in milk and other dairy products. Without these enzymes, the food would reach the intestines as larger molecules, unable to be absorbed into the body.
Other Digestive Enzymes
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The pancreas and the liver also produce digestive enzymes. The pancreas secretes amylase to further break down starches. It also secretes trypsin and nuclease to disintegrate proteins even more; protein molecules are complex structures that require multiple enzymes to reduce them to their most basic parts. The liver secretes bile, which acts as an emulsifier to allow fats and oils to become water-soluble for absorption into, and transfer within, the blood stream.
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References
- Photo Credit Image by Flickr.com, courtesy of Arnold Gatilao
