What Are Digestive Enzymes? - Functions & Types

What Are Digestive Enzymes? - Functions & Types
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  • 0:02 We 'Are' What We Eat
  • 1:09 Overview of Digestive Enzymes
  • 1:52 Types of Digestive Enzymes
  • 4:05 Lesson Summary
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Lesson Transcript
Instructor: Thomas Higginbotham

Tom has taught math / science at secondary & post-secondary, and a K-12 school administrator. He has a B.S. in Biology and a PhD in Curriculum & Instruction.

We are what we eat. But that doesn't mean our blood vessels are filled with giant chunks of hamburger. Thankfully, digestive enzymes help break down food into sizes small enough to be absorbed into our bloodstream. In this lesson, learn about these vitally important proteins.

We 'Are' What We Eat

The nutrients and components from our food provide not only the energy we use but the actual physical structure of our bodies. But our food does not generally come in a ready-to-use form. The animals and plants we eat tend to store energy in the form of large macromolecules like starches (plants) or glycogen (animals). Along with the mechanical breakdown of large food macromolecules, digestive enzymes help our food to be broken down into sizes and forms that are small enough to be absorbed into our bloodstream and usable to our bodies.

Digestive enzymes occur not only in humans and other animals, but also within carnivorous plants such as the Venus flycatcher (Dionaea muscipula) and sundew (Drosera rotundifolia). Digestive enzymes are also found within cell structures called lysosomes, where they perform the same function of breaking down larger molecules into smaller, usable ones. In this lesson, however, the focus will be on digestive enzymes in humans.

Overview of Digestive Enzymes

While digestive enzymes are found in most human cells' lysosomes, we'll focus here on those in the alimentary canal. The alimentary canal can be thought of as a one-way tube that starts at the mouth and ends at the anus. In order, the alimentary canal contains the mouth, esophagus, stomach, small intestine, large intestine, and anus. Believe it or not, digestive enzymes begin their work in the mouth.

If you hold a chewed up cracker in your mouth for a few minutes, you should notice the cracker tasting slightly sweeter as time progresses. This is because the enzyme amylases in saliva begin to break the cracker's starch down into its component sugar molecules.

Types of Digestive Enzymes

Amylases are one of the major categories of digestive enzymes. Not surprisingly, the major categories of enzymes follow the major biomolecule categories: carbohydrates (starches and sugars), proteins, and fats. Categories of digestive enzymes are listed:

  • Amylases break down starches and other carbohydrates into disaccharides, and digestive enzymes such as sucrase, lactase, and maltase break down disaccharides into absorbable simple sugars (monosaccharides)
  • Proteases break down proteins into peptides, and peptidases break those peptides down into absorbable amino acids.
  • Lipases break down fats into absorbable fatty acids and glycerol.

Let's take a closer look at how each of these types of digestive enzymes work to break down the major types of biomolecules in the body.

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