What is Amylase? - Definition & Function

Instructor: Catherine Konopka

Catherine has taught various college biology courses for 5 years at both 2-year and 4-year institutions. She has a Ph.D. in cell and molecular biology.

Have you ever wondered why your body can digest food so rapidly? One of the reasons is a specialized protein called amylase, which you can read more about in this lesson.

Water vs. Saliva

Let's do a thought experiment. Imagine you have two crackers. You put the first one in a glass of water. What happens to it? The cracker will get soggy, but it will still be there, nice and soggy, the next morning. Now, imagine that you put the second cracker in your mouth, but you don't chew it. What happens to it? If you think that it gets soggy really fast and pretty soon it will completely dissolve, you are right.

So, what's the difference between the first cracker in the glass and the second cracker inside your mouth? Both are in a wet environment - the first is in water and the second is in saliva, which is 99.5% water. However, saliva contains a very important molecule that can rapidly digest, or break down, the starch in the cracker. The molecule's name is amylase. Before we delve into the function of amylase and how it digests starch, let's first review the chemical nature of our food.

Macromolecules and Polymers

All living organisms are made up of just four types of large macromolecules: carbohydrates, proteins, lipids and nucleic acids. We eat living or once-living organisms, so our food is made up of those same four types of macromolecules. These macromolecules are polymers, which means they are composed of repeating units, called monomers. A pearl necklace can be thought of as a polymer, whose monomers are the pearls. Or you can think of a polymer as a train made up of train car monomers.

The monomers in macromolecules are connected by chemical bonds, similar to how pearls in a pearl necklace are connected to each other. Polymers can grow longer when monomers are added. On the other hand, polymers can also be broken down when monomers are taken off the chain. Polymers are broken down into monomers in a hydrolysis reaction.

Carbohydrates are polymers made up of sugar monomers. Starch is one type of carbohydrate and is composed of entirely glucose monomers. The glucose molecules are attached to each other by glycosidic bonds. When we digest the starch in the food we eat, we are breaking the glycosidic bonds between the glucose molecules.

Starch is a polymer (circled in green) that is composed of many glucose monomers (boxed in red.)
A starch polymer is composed of many glucose monomers bonded together

Enzymes Help Reactions Happen

There are billions of chemical reactions that happen in our body every day. But only very few of them would happen on their own without the help of enzymes. Enzymes are proteins that catalyze reactions, or help them proceed. Without enzymes we couldn't move, think or digest our food. In fact, there are about 10 enzymes in our digestive tract whose job it is to break down our food just so that we can absorb nutrients into our blood. Amylase is one of those enzymes.

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