Your pancreas plays an important role in the digestion of food. In this lesson, you will learn about the enzymes found in pancreatic juice that allow your body to break down carbohydrates, proteins and fats.
We previously learned that starches, which are a type of carbohydrate, begin to break down in the mouth due to enzymes found in your saliva. We also learned that proteins begin to break down in your stomach due to enzymes in the gastric juices.
However, from the mouth to the stomach, we have seen virtually no fats be digested. This will change as we move into the small intestine and learn how the secretions from the pancreas help in the digestive process.Chemical digestion kicks into high gear as we move into the first section of the small intestine, which we previously learned is called the duodenum. The duodenum is the area where many digestive juices enter the digestive tract.
Now, we see here that the pancreas is a triangular gland that extends across your abdomen and sits somewhat behind the stomach. The pancreas is a vital digestive organ because it produces a variety of enzymes that break down all of the major food groups. These enzymes are secreted into the duodenum along with a high concentration of bicarbonate. Bicarbonate makes the pancreatic secretions alkaline in nature. This flow of alkaline fluid into the small intestine helps to neutralize the acidic chyme that comes from the stomach. We previously learned that chyme is the term that we use for the partially digested food mass that has just passed out of the stomach.
Neutralizing the acidic chyme provides a better environment for activation of the pancreatic enzymes.We will look at the digestive enzymes that come from the pancreas in a moment, but before we do, it’s important to note that the pancreas also has an endocrine function. We previously learned that a gland can be either an exocrine gland, meaning that it secretes substances out through a duct, or an endocrine gland, meaning that it secretes hormones directly into the bloodstream. In the case of the pancreas, we see that it has both exocrine and endocrine functions. The pancreas is considered an exocrine gland because it secretes digestive juices through the pancreatic duct into the duodenum. It is also considered an endocrine gland because it produces and secretes the hormones insulin and glucagon into the bloodstream.
We previously learned that these two hormones play an important role in maintaining a normal blood sugar level.
When food enters the duodenum, it is deluged with pancreatic juice, which is defined as an alkaline secretion of the pancreas containing enzymes that aid in the digestion of proteins, carbohydrates and fats.
Because all of the major nutrients are either completely or partially broken down by enzymes from the pancreas, we see just how vital this organ is to digestion. This pancreatic juice contains enzymes that complete the digestion of starch called pancreatic amylase.In biochemistry, the most common way to name an enzyme is to add the suffix -ase. Not every enzyme ends in -ase, but if the suffix is present, you can feel safe to assume it is an enzyme. For example, you may recall that salivary amylase began digestion of starches in the mouth.
So, we see that ‘amylase’ is an enzyme that digests starches. You may also recall that the digestion of protein started in the stomach.
Trypsin, Chymotrypsin, Carboxypeptidase
Three enzymes found in pancreatic juice, called trypsin, chymotrypsin and carboxypeptidase, are the pancreatic enzymes that complete the digestion of proteins. Because proteins are held together by peptide bonds, these enzymes work by breaking peptide bonds.
Therefore, it might help you recall these enzymes by remembering that ‘trypsin’ and ‘chymotrypsin’ trip over and break the peptide bonds and that ‘carboxypeptidase’ has the word ‘peptide’ in its name.
To this point in the digestive system, we have not come across an enzyme that digests fats. However, pancreatic juice contains an enzyme that breaks down dietary fat molecules called pancreatic lipase.
Fat digestion is a little different than the digestion of carbohydrates and proteins. Because fats have not been broken down before entering the small intestine, we see that an additional substance called bile must first act on the fat molecule and break large fat droplets into smaller droplets so pancreatic lipase can be more effective. We’ll learn more about how bile helps pancreatic lipase do its job in a later lesson.
Let’s review. The pancreas is an important organ in digestion because it produces a variety of enzymes that break down all of the major food groups. In addition to the enzymes, your pancreas also secretes bicarbonate, which makes the pancreatic secretions alkaline in nature. This is helpful because it neutralizes the acidic chyme entering the small intestine from the stomach.
The pancreas is unusual in the fact that it is both an exocrine gland and an endocrine gland. It is considered an exocrine gland because it secretes digestive juices through the pancreatic duct, and it is considered to be an endocrine gland because it secretes the hormones insulin and glucagon into the bloodstream.The pancreatic juice contains enzymes that complete the digestion of starch called pancreatic amylase. It also contains pancreatic enzymes that complete the digestion of protein called trypsin, chymotrypsin and carboxypeptidase. We also see that pancreatic juice contains an enzyme that breaks down dietary fat molecules called pancreatic lipase.
Pancreatic lipase gets a little bit of help from bile, which first breaks down large fat droplets into smaller droplets.
Following this lesson, you will be able to:
- Describe the structure and function of the pancreas
- Explain the functions of bicarbonate and bile
- List several pancreatic enzymes and summarize their function