How Do Enzymes Help Digestion?

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson explores enzymes and their role in digestion. In this lesson we'll cover what an enzyme is, how digestion works, and how enzymes work together to break down food for your body.

Steps of Digestion

When you're enjoying a tasty snack while studying, that food goes from your plate, in your mouth, down to your stomach, and, eventually, to your entire body. This incredible journey is sponsored by your digestive system, a series of organs responsible for breaking down food into useable nutrients for the body. Before we can get into how enzymes help this process, let's take a quick look at each of the steps in digestion.

The first step of digestion happens in the mouth. Deliciously sweet carbohydrates--like cake, cookies, bread, and pasta--start their breakdown here. Next, the food is transported to the stomach through the esophagus, a long, narrow muscular tube that stretches from your mouth to your stomach. Once the food gets to the stomach, chemicals and enzymes start to eat away at the food. From the stomach, the mushed up food, or chyme, travels into the small intestine. Here's where the action happens. Food is further broken down through chemical digestion and nutrients from food are absorbed into the blood that circulates through our bodies. Accessory organs like the pancreas, liver, and gallbladder help out here too. Next, the large intestine absorbs water and sends the waste to the rectum for disposal.

digestive system

Now that we have a sense of the path food takes from start to finish, let's check out where enzymes join the digestive journey.

What Is an Enzyme?

Enzymes are tiny, beyond microscopic, proteins found all over your body that speed up chemical reactions. They can break things down, like in the digestive system, but they can also help build things in other parts of the body. Enzymes are crucial for your body to function. Without them, we couldn't be able to break down food, breathe, or even think! Now, let's find out how enzymes work in digestion.

Enzymes break down chemicals into other products needed by the body.
enzyme action

Enzymes in the Mouth and Stomach

Enzymes start the digestion process from the very beginning in the mouth. An enzyme called amylase starts breaking down carbohydrates right away. Digestion is a long process, though, and it continues in the stomach and finishes in the small intestine much later.

Enzymes start breaking down carbohydrate-rich foods like these right away as they are eaten.

Lipids, or fats, also begin their journey here, being broken down by another enzyme called lingual lipase. However, like carbohydrates, most digestion and absorption is completed in the small intestine.

The next step for food is the stomach, which is very acidic. In fact, your stomach acid could even dissolve iron nails! These powerful acids would destroy most enzymes, but your stomach has special enzymes. When you eat, cells in your stomach lining release a precursor for enzymes, which are activated by acid once in the stomach. Think of it like a sponge. When you get a sponge in a package, it's usually small and dry. But once you drop it in water, it expands and you can use it to scrub the gunk off your countertop. The precursor is converted to another enzyme, pepsin, which breaks up proteins in the stomach.

Acid activates special enzymes in the stomach to digest food.
stomach acid and enzymes

Enzymes in the Intestines

The next step of digestion occurs in the small intestine, aka the boss of nutrient absorption. In conjunction with the pancreas, liver, and gallbladder, the small intestine absorbs and breaks down the food with enzymes and chemicals. The pancreas secretes important enzymes into the small intestine, making it possible to digest fat and protein.

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